Thesis by Mazlinda SHM

INFLUENCE OF MONMORILONITE CLAY ON THE SETTING
REACTION AND COMPRESSIVE STRENGTH OF GLASS
POLYALKENOATE CEMENTS FOR LG3 (NON-SODIUM GLASS) AND
LG66 (WITH-SODIUM GLASS)

by

MAZLINDA BINTI SARIHASAN

A Project Submitted in a Partial Fulfillment of the Requirement

For Bachelor of Science (Honours), in Petroleum Chemistry

Department of Chemistry

Faculty of Science

Universiti Putra Malaysia

April 2011

INFLUENCE OF MONMORILONITE CLAY ON THE SETTING
REACTION AND COMPRESSIVE STRENGTH OF GLASS
POLYALKENOATE CEMENTS FOR LG3 (NON-SODIUM GLASS) AND
LG66 (WITH-SODIUM GLASS)

by

MAZLINDA BINTI SARIHASAN

(149586)

Approved by:

Project Supervisor:

……………………………………. Date:………………...

(DR.NORHAZLIN ZAINUDDIN)

Project Coordinator:

……………………………………. Date:………………..

(DR.NORHAZLIN ZAINUDDIN)

DECLARATION

I hereby declare that the thesis is based on my original work except for quotations and citations,

which have been duly acknowledged. I also declare that this thesis has not been previously or

concurrently submitted for any other degree at Universiti Putra Malaysia or other institutions.

……...………………………………

(MAZLINDA BINTI SARIHASAN)

Date:……………………………

ACKNOWLEDGEMENT

All praises to ALLAH the Almighty for giving me the strength to complete this study. The

special thanks dedicated to my helpful supervisor, Dr. Norhazlin Zainuddin. The supervision,

guidance, encouragement and support that she gave truly help the progression and smoothness

of my final year project. The co-operation is much indeed appreciated.

Special appreciation goes to my project’s senior, Nur’Izzah Md Nasir for her big contribution

during the progression of this project. I really hope that she can complete her study in master

level with flying colours.

Sincere thanks forwarded for staffs of Faculty of Science: Mrs Rusnani Amiruddin,

Mrs.Zaidina Md Daud and Mr. Then for their assistance in running my samples on the FTIR,

TGA and XRD analysis. Also, big thank to Faculty of Engineering and Institusi Teknologi

Maju (ITMA) for allowing me to do compressive test and grind my sample. A big contribution

from all staffs throughout my project is very great indeed.

I am grateful to my lovely parents, family, course-mate and friends for giving me great

support, inspiration, reminder and advice through all difficult time. Thanks all.

ABSTRACT

INFLUENCE OF MONMORILONITE CLAY ON THE SETTING REACTION AND
COMPRESSIVE STRENGTH OF GLASS POLYALKENOATE CEMENTS FOR LG3
(NON-SODIUM GLASS) AND LG66 (WITH-SODIUM GLASS)

By

MAZLINDA BT SARIHASAN

APRIL 2011

Supervisor : Dr.Norhazlin Bt Zainuddin

Faculty : Science UPM

Department : Chemistry

Several features such as mechanical, physical and chemical properties play vital role in

selection of dental cement. Glass ionomer cement (GIC) that is a modern version of silicate

cement becomes the most significant dental material due to the existence of these features. In

this study, the (GIC) also known as Glass Polyalkenoate Cement (GPC) was produced via acid-

base neutralization reaction of aqueous polyacrylic acid (PAA) with finely ground calcium

fluoro-alumino silicate glass powder. Two of glass formulation were used, LG3 (33.3 SiO2-22.2

Al2O3-11.1 P2O5-22.2 CaO-11.1 CaF2) and LG66 (33.3 SiO2-22.2 Al2O3-11.1 P2O5-17.8 CaO-

11.1 CaF2-4.4 Na2O). This study emphasized the influence of montmorillonite (MMT) on the

compressive strength of GPCs. For this study, it was found that 2.5 wt% is the best percentage

of MMT that could be mixed with GPC. The excess amount of MMT leads to difficulty in

mixing the glass powder and PAA and thus unable to mix homogenously. GPCs were

characterized using XRD, FTIR spectroscopy and TGA. The amorphous phases of GPCs were

proven from XRD pattern. From FTIR spectroscopy, the setting reaction of GPCs at various

aging time can be determined. The original glass powder give major absorption band around

920 cm-1 correspond to Si-O(Si) stretch. For PAA, strong band with medium width occurred in

the region 1700 – 1660 cm-1 was due to COOH stretch of carbonyl group. In GPC, new band

appears between 1710 cm-1 – 1390 cm_1. The appearance of this new peak was caused by the

formation of COO-M+ (M = Ca, Al) from the cross linking of metal ions with carboxylate group

of PAA. Band around 920 cm-1 which had formed earlier was disappeared as aging time

increase. This phenomenon was due to formation of Si-O-Si. This study found that the addition

of MMT improved the compressive strength of GPCs. The addition of MMT in LG3 and LG66

cements increased the compressive strength from 53 to 74 MPa and from 10 MPa to 66 MPa at

14 and 28 days aging time respectively. The presence of sodium influences the working time

and compressive strength at early of setting reaction. However, the compressive strength value

and setting reaction of both glasses become almost similar at 28 days aging time.

ABSTRAK

PENGARUH ‘MONMORILONITE CLAY’ TERHADAP ATURAN TINDAKBALAS
DAN DAYA MAMPATAN DALAM GELAS POLYALKENOAT SIMEN PADA GELAS
LG3 (TIADA KANDUNGAN SODIUM) DAN GELAS LG66 (DENGAN KANDUNGAN
SODIUM)

Oleh

MAZLINDA SARIHASAN

APRIL 2011

Penyelia : Dr.Norhazlin Bt Zainuddin

Fakulti : Sains UPM

Jabatan : Kimia

Beberapa ciri seperti sifat mekanik, fizikal dan kimia memainkan peranan penting dalam

pemilihan simen gigi. Gelas ionomer simen (GIC) merupakan versi moden simen silikat yang

penting kerana adanya ciri-ciri ini. Dalam kajian ini, GIC juga dikenali sebagai Gelas

Polialkenoat Simen (GPC) telah dihasilkan melalui tindakbalas penuetralan asid-bes poliakrilat

cecair (PAA) dengan serbuk kaca halus fluoro-alumino kalsium silikat. Dua formulasi gelas telah

digunakan, LG3 (33.3 SiO2-22.2 Al2O3-11.1 P2O5-22.2 CaO-11.1 CaF2) dan LG66 (33.3 SiO2-

22.2 Al2O3-11.1 P2O5-17.8 CaO-11.1 CaF2-4.4 Na2O). Kajian ini menekankan pengaruh

montmorilonit (MMT) terhadap daya mampatan GPC. Untuk kajian ini, didapati bahawa

peratusan pemberat 2.5 % adalah pemberat paling sesuai yang boleh dicampurkan dengan

dengan GPC. Jumlah yang berlebihan menyebabkan kesulitan dalam pencampuran serbuk gelas

dengan PAA dan tidak bercampuran secara homogen. Pencirian GPC dilakukan dengan

menggunakan analisis XRD, spektroskopi FTIR, dan TGA. Fasa amorf GPC dapat dibuktikan

melalui pola XRD. Daripada FTIR, aturan tindakbalas GPC pada pelbagai tempoh penuaan

dapat ditentukan. Serbuk gelas asli memberikan serapan utama pada panjang gelombang 920cm-1

yang menunjukkan renggangan pada ikatan Si-O(Si). Untuk PAA, puncak yang besar dan lebar

berlaku di kawasan panjang gelombang antara 1700 – 1660 cm-1 adalah selaras dengan kehadiran

kumpulan COOH. Dalam GPC pula, satu puncak baru muncul antara panjang gelombang 1770 –

1390 cm-1. Kemunculan puncak ini adalah disebabkan berlakunya pembentukan COO-M+ (M =

Ca, Al) dari persilangan ion logam dengan kumpulan karbosilik dari PAA. Puncak di sekitar

panjang gelombang 920 cm-1 yang terbentuk pada awalnya telah menghilang apabila masa

meningkat. Fenomena ini berlaku kerana pembentukan ikatan Si-O-Si. Secara umumnya,

penambahan MMT dapat meningkatkan kekuatan GPC. GPC daripada gelas LG3 tanpa dan

dengan penambahan MMT masing-masing memberikan nilai daya mampatan yang maksimum

sebanyak 53 dan 74 Mpa. GPC dari gelas LG66 memberikan daya mampatan 10 Mpa dengan

tiada penambahan MMT dan 66 Mpa dengan adaya penambahan MMT. Kehadiran sodium

mempengaruhi masa kerja dan daya mampatan pada awal aturan tindakbalas.

Walaubagaimanapun, nilai daya mampatan dan aturan tindakbalas pada kedua-dua gelas menjadi

sama pada tempoh penuaan 28 hari.

LIST OF TABLES

TABLES PAGE
1.1: Comparison among dental restorative materials 3

3.1: LG3 and LG66 composition in mole percent, % 22

3.2: Weight ratio of glass, PAA, MMT clay and water 24

4.1: Compressive strength of LG3 cement as a function of time 39

4.2: Compressive strength of LG66 cement as a function of time 39

LIST OF FIGURES

FIGURES PAGE
2.1: Classification of cement 7

2.2: Schematic depiction of the setting reaction of glass ionomer cements 9

2.3: Schematic representation of aluminium coordination states in glasses and GICs 14

4.1: XRD pattern for LG3 cement without and with addition of MMT 28

4.2: XRD pattern for LG66 cement without and with addition of MMT 29

4.3: Thermogram for LG3 glass 30

4.4: Thermogram for LG66 glass 31

4.5: Thermogram of PAA 32

4.6: Thermogram of MMT 32

4.7: Thermogram of LG3 glass without addition of MMT 35

4.8: Thermogram of LG66 glass without addition of MMT 35

4.9: Thermogram of LG3 glass with addition of MMT 36

4.10: Thermogram of LG66 glass with addition of MMT 36

4.11: Compressive strength of LG3 cement without and with addition of MMT 40

4.12: Compressive strength of LG66 cement without and with addition of MMT 40

4.13: Infrared spectrum for LG3 glass 44

4.14: Infrared spectrum for LG66 glass 44

4.15: Infrared spectrum for polyacrylic acid, PAA 45

4.16: Infrared spectra of LG3 cement without MMT addition with aging time from 5 47
minutes to 28 days

4.17: Infrared spectra of LG66 cement without MMT addition with aging time from 49
5 minutes to 28 days
4.18: Comparison of FTIR spectra of LG3 cement and LG66 cement without MMT 53
at 5 minutes aging time
4.19: Infrared spectrum of MMT 54

4.20: Infrared spectra of LG3 glass with and without addition of MMT at 5 minutes 55

4.21: Infrared spectra of LG66 glass with and without addition of MMT at 55
5 minutes

LIST OF ABBREVIATIONS

ADA-MMT 12-amino-dodecanoicacid treated montmorillonite

Ca-MMT Calcium montmorillonite

FTIR Fourier transform infrared

GICs Glass ionomer cement

GPCs Glass polyalkenoate cement

IR Infrared

MAS-NMR Magic-angle spinning nuclear magnetic resonance

MMT Montmorillonite

MPa Mega Pascal

ISO International Organization for Standardization

PAA Polyacrylic acid

TEM Transmission electron microscopy

TGA Thermal gravimetric analysis

Wt% Weight percent

XRD X-Ray diffraction

CHAPTER 1

INTRODUCTION

1.1 Dental Cement

Dental cement is a kind of material used as clinical dentistry to restore lost tooth functions due to

cavity formation. Therefore, it must have properties that close to natural tooth. In studies of

dental cement, several terms have to be understood such: chemistry of the setting reaction,

consistency in proportion of powder to liquid ratio in mixing cements, maximum solubility and

disintegration, dimensional change, working and setting times, bonding strength for their

intended use (MPa), optimum film thickness, thermal and electric conductivity, amount of heat

generated during setting, and safety (should not be toxic, carcinogenic, mutagenic, irritating, or

sensitizing).

Nowadays, dental researcher have wide opportunity to develop the newer cements and achieve

better understanding of the clinical and biological performance of cements since it is necessary to

produce the ideal cement to use in dentistry. There are many types of dental cement are available

but none of them are perfect (Nicholson and Anstice, 1999). Even thought the amount of dental

cement required is so small but clinical investigators and investigations on cement performance

still on demand in order to improve the properties of dental restorative materials. Changes in the

pattern of caries and the emergence of an aging, longer-lived population in many countries also

will increase the need for the better quality, effective and durable cementing agents.

Dental cement has multiplicity applications since it was ideal artificial materials that have roles

as luting agents, cavity linings and bases, and restorations for teeth thus make them perhaps the

most important materials in clinical dentistry. Through available dental cement, glass-ionomer

achieved the best number of application since it comes with good adhesion and ability to release

fluoride. Other clinical application of glass ionomer include in various non dental application

such as ear, nose, throat surgery and craniofacial reconstruction (Nicholson, 1988).

In this current age, improved formulation of glass ionomer cement have gone through deep

investigation since it shows unique properties such as adhesion to wet tooth structure and base

metals, anticariogenic properties due to release of fluoride, thermal compatibility with tooth

structure, biocompatibility and low cytotoxicity ( Moshaverinia et al., 2011). Besides, GPCs also

have been recognized to have thermal compatibility with tooth enamel (Craig, 1997) and provide

a better clinical retention of non-carious cervical restorations as compared with conventional

adhesives (Peumans et al., 2005). From the clinical point of view, this cement has ability to self-

hardening, chemically bonded to dental tissues, excellent translucency thus suitable for several

applications in the dental practice.

Currently, there are four major dental restorative materials being used in the field of dentistry

such are: amalgam, resin composite, conventional glass ionomer cement (CGIC), and resin

modified GIC (RMGIC). CGIC and RMGIC are classification of GIC. Several comparisons

among these materials are shown on table below:

Table 1: Comparison among dental restorative materials (Jun Zhao,2009)

Properties Dentin Amalgam Resin CGIC RMGIC
composite
Compressive 297 310 ~ 445 280 ~ 390 235.6 212.7
Strength
(MPa)

Tensile 98.7 27.3-54.7 32.0 ~ 63.8 8.7 ~ 12.9 12.6 ~ 14.2
Strength
(MPa)
Flexural 212.9 119-146 61.4 ~ 139.4 11.1 ~ 31.4 71.1 ~ 82.1
strength
(MPa)
Wear Resistance - 0.3 0.8 1.8 1.2
(nm/cycle)
Biocompatibility - Controversial Poor Good Medium
Setting Time - 2~6 <1 4 <1
(min)
Thermal 8.3-11.4³ 22.1 ~ 28.0 25-68 <1 25
Expansion
(10-6·°C-1)
1.364 0 54.0 2.61 1.3 ~ 1.6 0.49 ~ 0.66
Thermal
Conductivity
(ᵒC.m2)
Esthetic - Bad Good Good Good
Property
Durability - Durable Durable Low Low

Jun Zhao (2009) had summarized and did several comparisons between all above materials. Ideal

compressive, tensile and flexural strength of dental cement are very important to give proper

function of the cement itself. From the compressive strength, it clearly showed that amalgam has

the highest compressive strength compare to other. For the tensile strength and flexural strength,

amalgam is significantly higher than any of current dental restorative materials. CGIC or

RMGIC is much weaker than amalgam or resin composite. Amalgam show less wear resistance

compare with other restorative materials. Wear is the tribological process which could cause loss

of material due to the interaction of opposing surfaces (Mair et al., 1996). The degree of wear

determines the usage of dental restoratives. For instance, GIC cannot be used for class II

restorations because greater occlusive and abrasive wear are present in the area. However,

addition of suitable type and amount of clay could decrease the wear resistance of the CGIC and

RMGIC (Dowling et al., 2006).

William (1987) defined biocompatibility as the ability of a material to perform with appropriate

host respond in a specific application. Regarding to health and environmental concerns, CGIC is

the best material since it have good biocompatibility than RMGIC and the other two materials.

Regarding to the unique properties, GPCs can be used as an alternative for the replacement of

amalgam that susceptible to corrosion, toxicity, non-tooth coloured and non adhesive. However,

GPCs face with some limitation due to brittleness, poor fracture toughness material and

sensitivity to moisture in the early stages of the placement (Moshaverinia et al., 2011). Major

disadvantage of GIC is the mechanical weakness. This cement can achieve Young’s modulus

values in the range 4-8 GPa and flexural strength between 25-35 MPa (Kenny and Buggy, 2003).

GIC have inferior fracture toughness compared to amalgam and therefore limited its application

as posterior filling material for the class I and II cavities (Lewis, 1989).

1.2 Significance of the study

Glass polyalkenoate cements (GPCs) are important material for the modern clinical dentistry that

remain success until today as result of their capacity to chemically bond to the apatite mineral of

teeth, avoid second carries, inherently good adhesion and their ability to release fluoride.

However as mentioned before, GPCs have limitation in terms of brittleness, poor inferior

fracture toughness and wear resistance compared to amalgams thus limited its application to low-

stress bearing sites and use as filling material on front teeth only. Amalgam has been applied for

quite a long time in dental clinics. But then, in oral environment amalgam are susceptible to

corrosion, non-tooth coloured and the presence of mercury in its composition bothers health

professionals and dental patients. This lead to a set of fundamental should be considered by

dental profession to investigate alternative of restorative material to replace the application of

amalgam. Therefore, the aim of this laboratory study was to investigate GPCs associated with

sufficient mechanical strength that is essential for the proper function of dental restoratives

beside to follow its setting reaction.

1.3 Objectives of study

The main objectives of this study were:

1. To synthesize and characterize GPCs with the addition of MMT.

2. To study the influence of MMT clay on the compressive strength of GPCs.

3. To investigate the influence of Na on the setting reaction of cement

CHAPTER 2

LITERATURE REVIEW

2.1 Glass Polyalkenoate Cement (GPCs)

Glass polyalkenoate cement (GPC) is also known as water based glass ionomer cement (GIC).

Although named as glass ionomer cement, there is evidence that the structure of the GIC does

not fully exhibit the properties of ionomer (Milne et al.,1997). GICs were developed in the late

1960s at the Laboratory of Government Chemist, London, United Kingdom (Wilson and Crisp,

1972). Figure 1 shows that GICs are composed of glass powder which is alumino-silicate glass

and aqueous solution of polyacrylic acid.

Figure 2.1: Classification of cement (3M ESPE in Technical Product Profile)

GPCs became well known in dental community due to its unique properties such are adhere

directly to tooth structure and base metals , anticariogenic due to release of fluoride (Forsten,

1977), thermal compatibility with tooth enamel and dentin due to low coefficients of thermal

expansion similar to that of tooth structure minimized microleakage at the tooth–enamel

interface due to low shrinkage (Craig, 1997), biological compatibility (Sasanaluckit et al., 1993)

and have low cytotoxicity (Hume et al., 1988).

GPC consist of a basic glass powder and a water-soluble acidic polymer, such as poly(acrylic

acid). The main structure of glass is still alumina and silica which form the skeletal bone of the

glass. When glass powder mixed with water, acid degrades the network structure and releasing

metal ions that further determine the extent of crosslinking and polysalt bridge in the polysalt

matrix (De Barra and Hill, 1998). The general equation for the reaction between the glass and

PAA is: as:

MO. SiO2 + H2A MA + SiO2 + H2O

Where M is a metal ion such are Ca2+, Sr2+, or Al3+ within the glass and A is the conjugated base

of the acid (Noort, 1994).

Figure 2.2: Schematic depiction of the setting reaction of glass ionomer cements
(3M ESPE in Technical Product Profile)

Once basic glass fillers and acidic poly(acryliclic acid) solution are mixed together, the outer

layer of filler particle reacts with the acid via neutralization and involves initial formation of

calcium or strontium polyacrylate and later formation of aluminium polyacrylate (Beata et al.,

2007) Multi-charged cations (Al3+ and Ca2+) are then released from the glass particles. These

released cations are chelated by the carboxylate groups and crosslink with PAA chain (Kenny

and Buggy, 2003). The COO− groups and the released Al3+ and Ca2+ ions enables cross linking

of these chains, giving a solid network around the glass particles. The binding of the COO−

groups with Ca2+ ions from the enamel occur and form a chemical bond between the cement and

the tooth structure (Tjalling et al., 2006). Reaction involved is acid-base reaction where glass

being a base in sense that it accepts protons from acid even though it is not soluble in water. The

number and type of anions and cations released from the glass particle will determine the extent

of cross linking in polysalt matrix (De Barra, 2008).

However, GPC also consists of unreacted glass particle in that complex matrix which include

calcium and aluminium polyacrylates (Crisp et al., 1974) in the form of inorganic network. This

network has been suggested to be responsible for maturation process that will lead to the

increasing of compressive strength and binding water into the structure (Nicholson, 1988).

GIC is known to contain fluoride and there are very extensive literatures on fluoride release from

GIC. Fluorides are used to prevent caries and secondary caries. Secondary caries rarely

developed adjacent to silicate cement restorative fillings. The leached fluoride is taken up by that

adjacent enamel to reduce secondary caries formation (Guida et al., 2002). Glass ionomer

cements release fluoride ions and the effect of the released fluorides on bacteria metabolism has

been reported (Hoszek et al., 2008). Noriko and Miroslav (2010) has been reported that the

release of fluoride ions from glass ionomer cements that associated with titanium can be

generated or recharged by the use of solutions of high fluoride concentration and can be

continued for longer than a year.

The properties of cement formed depend on the glass composition, powder size, polyacid

concentration, polyacid molar mass and the reaction time. Some researchers conclude that the

properties of the set of cement can be explained entirely by the formation of ionically crosslinked

polymer chain. However, the exact relationship between the composition of the glass and these

properties is not yet fully understood (De Maeyer et al., 2005).

For glass with sodium, Na content, the resulted cement likely to have disportionate influence on

its properties ( De Barra and Hill, 1998). Na usually added to lower the melt temperature during

manufacturing process. However, glass with higher amount of sodium content will had

opalescent apprearance and promotes phase separation during quenching from the melt. Hill et

al. (1995) have shown that crosslinking in polysalt matrix for cement based on sodium

containing glasses was disrupted, thus facilitating diffusion and exchange of fluoride ions for

hydroxyl ion.

Reduction in the powder particle size of up to 10 mm will result in a smoother surface. With

regard to surface roughness, it is considered that the smoother surface discourages the occurrence

of defects (such as cracks and flaws) that cause stress concentrations and ultimately promotes the

fracture resistance (Mitsuhashi et al., 2002).

2.2 Setting Reaction of GPCs

Setting reaction of cement is significant for the development of glass materials for their correct

application in dentistry. There are some issues among the researchers on how the setting reaction

mechanism takes place. Some researchers believe that there are three steps could lead to

complete setting reaction (Nicholson et al., 1998). Firstly, the acid degrades the glass structure

and leading to release of cations such Ca2+ and Al3+. Secondly, step is rapid reaction between

Ca2+ and Al3+ ions and polyacid chain. These reactions enable more gradual release of latter ion

from anionic complex. The latter can act as a network modifier by forming Si-O-Na or Si-O-Ca

bonds, thus breaking down the silica network and rendering the glass more basic. Further

reaction of metal ions will result crosslink between metal ions and polyacid. The bivalent and

Al3+ ions that are leached from the glass form a metal polyalkenoate gel, which acts as a binding

matrix in the cement (De Maeyer et al., 1998). Thirdly, the reconstruction of the silicate network

of that associated with maturation of glass to yield a matrix of increasing strength, greater

resistance and improved translucency (Matsuya et al., 1996).

Another theory of setting reaction is discussed by Wilson and McLean (1988) where they found

that the setting within cement occurs via two steps mechanism. The primary step is hardening

step after glass and aqueous polyacid mix each other about 3-5 minutes. Through FTIR study,

Crisp and Wilson (1974) assigned that a calcium salt was formed leading to gelation at initial

step. From study of Cook (1983) suggested that Al3+ ions are also involved in the initial setting

reaction. The presence of aluminium in the glass structure is important to create negative sites to

be attacked by polyacid. Disintegration of glass release Al3+ ions that will enter the tetrahedron

silicate network and leave a net negative charge on the structure (Nicholson et al., 1998). Despite

from this, Nicholson et al., (1998) also mentioned that even though Al3+ released early in the

initial setting, a delay and formation of aluminium polyacrylate species is depend on the

decomposition of the aluminium in the aqueous solution. The secondary mechanism is post-

hardening steps. This step is involves the formation aluminum salt species and contribute to the

improvement of mechanical properties that measured relative with time.

Glass composition is a major factor that influences the setting reaction. Since GPCs were easily

manipulated, the composition such Al2O3/SiO2 ratio can be varied prior to specific application.

Other than that setting reaction also depend on the temperature, storage medium, and storage

time. Tjalling et al.(2005) study was investigated the influence of temperature on the setting

time. Increase in temperature will speed up the setting reaction significantly. Their study proved

that working and setting time decreased with increasing temperature showed by rheometer. It

was concluded that a temperature between 333 and 343K almost sets conventional GIC’s on

command. Work done by Roemhildt et al.(2006) verify the previous work as the working time

decreased progressively: 28.2, 14.2, 8.6, 6.3, and 4.4 min, with increasing temperature. Similarly,

the setting time decreased: 64.4, 27.5, 17.92, 12.8, and 10.2 min, as the temperature increased.

The rate of setting can be affected by the particle size of the glass. A glass with finer particle

sizes will set faster and have a shorter working time (Nicholson et al., 1998); that is time

indicates the end of moldability without damage to the developing cement structure (Driessens et

al., 1995). Water also the main constituent in setting reaction of glass. As setting continues,

water hydrates the matrix. The hydration is important in the formation of a stable gel structure

and building the strength of the cement.

There are several acceptable techniques have been used to characterize setting reaction of cement

such as MAS-NMR spectroscopy (Prosser et al., 1982), Fourier transform infrared spectroscopy

(FTIR) (Nicholson et al., 1988), Raman spectroscopy (Young et al., 2002), pH study

(Stamboulis et al., 2004), X-ray Diffraction (XRD) (Robert and Atul, 1980) analysis and

Transmission Electron Microscopy (TEM) (Hatton and Brook, 1992).

The advantages of MAS-NMR spectroscopy are it can probe the structure of amorphous glasses

and determine the molecular structure, environment of species and their next neighbors. The

NMR data verified phase purity, specify one molecule per asymmetric unit and provide an initial

structural model including relative stereochemistry and molecular conformation of the glass

cement formed (Aliev and Law, 2007). The most important MAS-NMR can show that A13+ ion

was tetrahedrally coordinated by oxygen in theoriginal glass, but a part of the A13+ ion was

octahedrally coordinated after hardening to form Al polyacrylate gel. In the initial glass

aluminium is mostly present in a four coordination or tetrahedral state, Al(IV), and switches to a

six coordination or octahedral state, Al(VI), when crosslinking the polymeric chains (Matsuya et

al., 1996). Figure 3 illustrates the aluminium coordination in each environment that is Al(IV) in

glass and Al(VI) in cement.

Figure 2.3: Schematic representation of aluminium coordination states in glasses and GICs
(Munhoz et al., 2010)

The A13+ ions leached into the cement matrix form aluminium carboxylate species (Pires et al.,

2007). Besides, by using MAS-NMR, Si measurements also can be used as an indirect structural

probe, since the chemical shift of the silicon nucleus is dependent on the connectivity of its

tetrahedral structure and number of aluminium atoms in their second coordination sphere

(Engelhardt and Koller, 1994).

From FTIR, we could determine setting reaction by assigning particular peaks that develop due

to acid-base reaction. Crisp S et al.(1974) suggested FTIR studies revealed a calcium salt was

formed during the early stage of reaction. However, this kind of technique only suitable for semi-

quantitative analysis since the loss of carbonyl group absorption band from the carboxylic acid

group during the neutralization can be masked by the asymmetric COO salt band (Nicholson et

al., 1988). The FTIR result also could indicate the structural change of pattern in the silicate

network of the glass. The absorption band between 1350 and 800 cm-1 moved toward higher

frequency for longer aging time and finally achieve a maximum around 1060 cm-1 with a

shoulder at 950 cm-1.

pH also can be used to indicate the neutralization reaction between glass and polyacids.

However, pH study was not use widely (Crisp and Wilson, 1974). For XRD and TEM analysis,

its serve better understanding of the setting reaction within GPCs. With using XRD, change in

phase composition that is expected to continue over a much longer period of time can be

observed. From TEM, we could see the existence of the inorganic network that important to

explain the fact that glass forming-elements such as silicon have been found throughout the

matrix (Hatton and Brook, 1992).

2.3 Hardening and Maturing of GPCs

Hardening of GPCs is based on the crosslinking of released metal cations such as Ca2+ and Al3+

with PAA. This also lead to the reconstruction of the silicate network of the glass (Nicholson, et

al. 1998). This network consist of Si-O-Si bonds which is four-fold coordinated aluminum has

partly replace Si to form Si-O-Al network as A13+ ions leached from the glass. The new formed

network in silica serves negative sites and become available as attack site by an acid (De Meyer

et al.,1988). This step also known as gelation where the reaction promotes subsequent leaching

of the glass modifier cations into the cement matrix. Depend on the glass composition, some

cations such Na+ and Ca2+ can be released from the glass and this will form other networks such

Si-O-Na or Si-O-Ca. As a result, another Si network will break and causes the glass become

more basic and able serves another negative charge. A13+ ions that are leached from the glass

upon acid will further attack react with the polyacid anion to form a metal polyalkenoate gel or

polymer interconnected by the cations. Barry et al. (1979) showed that the leaching of Al3+ from

the glass particles is more difficult than Ca2+. Thus, polyalkenoate forms stronger bonds with

trivalent (A13+) than with bivalent (Ca2+) ions, which then form more mobile bond and less

solvated Ca2+ ion (Nicholson et al., 1998)

In initial hardening, GPC undergo maturation rapidly as a result from bond reconstruction. The

gel formation could occur within several minutes. From the FTIR, the Ca 2+ cations form

carboxylates immediately during gelation, Al3+ cations only react with the polymeric chains

later, during maturation (Matsuya et al., 1996). Recent work by Pires et al. (2007) on the setting

chemistry of commercial glass–ionomer cement showed the existence of three different Al

species in the glass particles that had different leaching characteristics. Thus, faster leaching of

five and six coordinated Al species takes place and causes Al3+ in four coordinate environments

is more resistant to acid attack. Despite from this, the study proved that it is not only Al3+ from

four coordinate environments is leached into the cement matrix. As previously reported by

Matsuya et al. (1996) Al3+ also comes from five and six coordinate environments. Part of

aluminium ions leached into the cement matrix and formed aluminium carboxylate species.

Gradual reconstruction in the cement matrix is leading to the increase of compressive strength

which arises gradually over some period time to a maximum value as explained by Wilson and

McLean, (1988). Glass ionomer typically can reach a compressive strength of 180-220Mpa at

one day and may rise over time. Translucency is also change and become more like natural tooth

material as a result of maturing (Billington and Williams, 1991)

2.4 FTIR technique analysis

The setting reaction of glass ionomer can be investigated according to infrared spectroscopy due

to the structural hardening of cement as glass react with polyacid solution. To see the change

pattern of absorption band, the original powder of the experimental cement must be compared

with the glass produced with different aging time. According to Matsuya et al.(1996) the

absorption of original powder of the experimental cement is totally different with glasses that

have been produced. Original glass powder had a maximum absorption is around 920 cm-1.

However, the maximum tended to shift toward higher frequency with time, and finally the broad

band showed a maximum at 1050 cm–l with a shoulder at 950 cm-1. At early stage of the reaction,

a strong absorption band was observed at 1730 cm-1. This absorption due to the C=O stretch

peak. Then, as time elapsed, a new band appeared around 1620 cm-1, and its intensity rapidly

increased within 1 hour (Matsuya et al., 1996). During the reaction also, the C=O stretch peak

decrease in intensity as the acids are neutralize with glass (Tomlinson et al., 2007). Another

feature is the maximum of a broad band between 1350 and 800 cm-1 moved toward higher

frequency with time, and finally the band showed a maximum around 1060 cm-1 with a shoulder

at 950 cm-1. The spectral pattern was quite similar to that of hydrated silica gel, which had a

strong band around 1050cm-1 due to the Si-O-Si stretching vibration (Hanna and Su, 1964) and a

medium band at 950 cm-1 due to Si-OH deformation vibration (Soda , 1961). This was happen

due to the increasing of degree of polymerization during the hardening.

Then, in terms of silicate network, characteristic band appeared around 1000 cm-1 was then

shifted toward high frequency relative with time. The same fact also ever revealed by Soda

(1961) and Efimov (1996) where the strong band between 1000 and 1200 cm-1 in the spectra

present due to the characteristic of the asymmetric stretching vibration of Si-O. These result also

supported by Matsuya et al. (1996) in which band profile can be observed within this range and

stated that the absorptions near 1180 cm-1 and between 1018 and 1073 cm-1 both originate from

the asymmetric Si-O stretching. The appearance of the band near 800 cm-1 and the decrease of

the band intensity near 730 cm-1 were related to the Al and other extraneous ions from the silica

network, resulting in a shift of the symmetric Si-O stretching vibration band (Farmer et al.,

1979).

As water also the main constituent in the formation of GPCs, the intensity of H-O-H bending

peak also appear at early of setting reaction (Nicholson et al., 1998). Band near 1640 cm-1 that

appears after leaching is caused by the bending vibration of water (Davis and Tomozawa, 1996).

De Maeyer et al. (1998) whose work with variety types of acid degradable glasses, they found

that intensity of this band vibration is higher for the glasses exhibiting significant modifications

of the Si-O band profiles. Water is probably included in the sample, since it apparently cannot be

removed by drying (De Maeyer et al. 2002).

2.5 Compressive strength of GPCs

There are four important mechanical properties need to be determined such hardness,

dimensional stability, compressive and flexural strength. Compressive strength testing is widely

used for evaluating brittle material such as glass ionomer cement. Loof J et al.(2003) already

stated the necessary for mechanical properties according to ISO standard 4049 and 9917.

International standard 4049 specifically designed for composite and 9917 for dental evaluation

for GIC. These test were done by using an INSTRON Universal instrument which associated

with flattened stainless steel discs on the top and bottom of sample to compensate determined

height and diameter cylindrical GIC.

Based on Loof et al. (2003), mechanical strength depends on important parameter that is the

grain size of the filler. A smaller filler grain size such microsize gives the higher hardness than

coarser. Besides, it also could improve the dimensional stability due to the lower expansion. Fine

grain size yielded expansion in the interval 0-0.1% compared with coarse grain size with 0.1-

0.2% interval after 4 month. This study was also had been investigate the compression strength

for different form of GPC. GPC with fine grain size filler have compressive strength to be 300

MPa and with coarse grain size to be 160 Mpa.

To investigate mechanical properties such compressive strength of cement, Lucksanasombool et

al. (2002) developed a study to set GIC for different time setting before exposure to aqueous

environment. Some GPC have been used and the result is invariant strength obtained with aging

time of GIC. Previously, Couston (1981) also did some condition of aqueous environment and

obtained increase in compressive strength as aging time become longer. However, Cattini-

Lorente et al.(1993) come with their statement that compressive strength probably due to the

wide variation in GIC composition itself as they work in various commercial GIC.

Cattani-Lorente et al. (1993), studied the mechanical properties of GICs when stored in water at

different time aging. They found four different pattern changes of the mechanical properties for

various type of GIC found when stored in water as the function of time. They are an increase in

strength to an upper limit value, a gain in strength over a period of 2 or 6 months, followed by

decrease, a continuous decrease in strength with time, and an invariable strength of GIC. This

study also concluded the strengthening of GIC with time resulted from the influence of

crosslinking in polymer matrix and build up of a silica gel phase, whereas weakening resulted

from the erosion and the plasticizing effect of water.

There were many other factors that influence compressive strength of GIC. Nicholson et al.

(1998) studies reported cement has various compressive strengths depend on the concentration of

lactic acid used to form the cement. They also reported that the inorganic network that develop in

silicon glass also responsible in maturation processes which will lead to increment in

compressive strength.

In contrast with this statement, De Barra and Hill (1998) reported the existence of inorganic

network do not have significant influence and might be it need to be balanced against the other

strong evidence for the important of the polymer component on the mechanical properties. The

exposure to aqueous environment has been shown to have deleterious effects on the mechanical

properties of GIC relative to the disturbance of Al3+ ions activity, which play a major role in

crosslinking polymerization of the PAA (Kobayashi et al., 2000). Crosslinking reaction is a

continuous process evident by the increase in mechanical properties of the cement with time.

Polymer has been shown to influence the toughness of the set cement (Wilson, 1972).

CHAPTER 3
MATERIALS AND METHODS

3.1 Materials

Two types of glass formulation were used in this study labeled as LG3 and LG66. Both of these

glasses were prepared at the Imperial College, London. The glass consists of silica (SiO2),

alumina (Al2O3), phosphorus pentoxide (P2O5), calcium oxide (CaO), calcium fluoride (CaF2),

and sodium oxide (Na2O). The mole percent of the glasses composition were shown below.

Table 3.1: LG3 and LG66 composition in mole percent, %.

Glass Code SiO2 Al2O3 P2O5 CaO CaF2 Na2O

LG3 33.3 22.2 11.1 22.2 11.1 -

LG66 33.3 22.2 11.1 17.8 11.1 4.4

The medical grade freeze-died PAA (Mw~80,000) was used for cement preparation and was

supplied by Advance Healthcare, Kent, England. Ethanol, liquid nitrogen and distilled water

were used throughout the experiment in propose to dehydrate the cement, terminate setting

reaction, and as reaction medium respectively.

3.2 Methodology

3.2.1 Preparation of glass

Both glass powders were prepared in the required amounts. The glasses were produced by

melting the reagents: silica (SiO2), alumina (Al2O3), phosphorus pentoxide (P2O5), calcium oxide

(CaO), calcium fluoride (CaF2), and sodium oxide (Na2O) in a platinum/rhodium or mullite

crucible at high temperature between 1300-1550⁰C for 2 hours. The resulting melts were rapidly

poured into water. The glass frit was collected and dried overnight in an oven at 100ºC. The glass

frit produced was ground by using Gyro Mill (Glen Creston Gyro Mill, Middlesex, England) and

sieved to a fine particle size of less than 45 μm for preparation of GPCs (Zainuddin N et al.,

2009).

3.2.2 Synthesis of GPCs

The preparations of the cements were divided into two parts:

1) GPCs without MMT clay

2) GPCs with MMT clay

GPCs without MMT clay

Both types of cement were formed by mixing the glass with poly(acrylic acid) and distilled water

with fixed ratio 2:1:1. For example, 0.5g of glass mixed with 0.25g of PAA and 0.25g of distilled

water. The mixtures were mixed homogenously and allowed to set at 37 C in the oven for 1 hour.

The cement was then soaked in water at 37C in the oven for the required ageing time. Time

intervals were used to study the setting reaction of the GPCs: 5 minutes, 10 minutes, 15 minutes,

30 minutes, 1hour, 6 hours, 1 day, 7 days, 14 days and 28 days. For cements were with aging

time less than 1 hour, termination of the reaction was done by using liquid nitrogen followed by

dehydration with ethanol. Then, the cements were ground to fine powder for FTIR analysis.

GPCs with MMT clay

The determination of the optimum amount of MMT can be loaded to the glasses was studied.

The weight percent of MMT clay was correlated with the total amount of glass and PAA. The

weight ratio used in this study is shown in Table 3.2 such below:

Table 3.2: Weight ratio of glass, PAA, MMT clay and water

Glass LG3/LG66 PAA MMT clay water
2 1 0.5, 1.0, 1.5, 2.5wt% 1

It was found that the best ratio of MMT can mix with GPCs is 2.5 wt%. Above this value, the
cement will face the difficulties in mixing. Similar procedure was done as preparation of GPCs
without MMT.

3.3 Characterization of GPCs

3.3.1 X-Ray Diffraction (XRD)

XRD is a non-destructive analytical technique for identification and quantitative measurement

for various phases. Recognition of amorphous or crystalline phase of GPCs with and without

addition of MMT was determined. XRD pattern was obtained by automated Shimadzu

Diffractometer XRD-6000 model by continuous scanning at rate 2º/min.

3.3.2 Thermal Gravimetric Analysis (TGA)

Thermogravimetric analysis is an experimental technique to investigate the behavior and stability

of material as function of temperature. Thermal stability of glass LG3, LG66, MMT clay, PAA

and GPCs were analyzed. TGA analysis was obtained using a computerized Perkin-Elmer

Thermal Analysis system. Thermograms were recorded from room temperature to 800ºC at

heating rate 1°C/min and nitrogen gas as sample purge gas.

3.3.3 Compressive Strength Test

The compressive test of the cements was done on the cylindrical specimens. The cement was

mixed and packed in a mold with 6 mm height and 4 mm diameter. Two blocks of stainless steel

were used to compress cement compactly. The resulting cement was allowed to set for 1hour at

37⁰C inside the test mould in the oven. Then, the cement was kept in water for 1 to 28 days prior

to compressive test. The diameter and length of each specimen were first measured with a

micrometer. The specimen was placed between steel plates of INSTRON compressive machine.

The specimen was tested with 5kN load cell at a loading rate of 1 mm/min.

3.3.4 Fourier-Transform Infrared (FTIR)

Study on the setting reaction of the cements was done using FTIR spectroscopy. FTIR spectra of

the GPCs, MMT and PAA were recorded in the range 200-4000 cm-1 by using Perkin Elmer

FTIR spectrophotometer associated with UATR accessory.

CHAPTER 4

RESULT AND DISCUSSION

In this study, GPC phase was determined by X-Ray Diffraction (XRD) analysis. The setting

reaction of GPC was done by using Fourier Transform Infrared Spectroscopy (FTIR). The

compressive strength of GPC was evaluated by INSTRON compressive machine. The last,

thermal stability of GPC, MMT and PAA were characterized by computerized Perkin-Elmer

Thermal Analysis.

4.1 Analysis of X-Ray Diffraction (XRD)

XRD is an analytical technique for identification of various crystalline forms or known as

‘phases’. The X-ray diffraction studies were conducted on GPC without and with addition of

MMT.

Figure 4.1 and 4.2 show the XRD pattern for LG3 glass cement and LG66 glass cement

respectively. All pattern show the broad peak that represent the non- crystalline amorphous

phases. Amorphous is the condition where the atoms arranged in a random order. This finding

was similar with Wood and Hill (1991) which mentioned that alumina glasses will exhibit the

broad peak in XRD profile. Previous study by Zainuddin N (2009) was also revealing the same

XRD pattern for both glasses.

From the entire XRD pattern, there were no significant difference between LG3 cement and

LG66 cement. Similar pattern was observed with the addition of MMT into both glasses. These

similarities were probably due to small amount of MMT (2.5 wt %) in the cement formulation

which did not influence the XRD profile of the original glass cement.

Intensity (a.u)

With
MMT

Without
MMT

2-Theta (Deg/°)

Figure 4.1: XRD patterns for LG3 cement without and with addition of MMT

Intensity (a.u)

With
MMT

Without
MMT

2-Theta (Deg/°)

Figure 4.2: XRD patterns for LG66 cement without and with addition of MMT

4.2 Analysis of Thermal Gravimetric Analysis (TGA)

The thermo gravimetric analysis (TGA) is the analytical measurement to measure the amount,

rate of change in the weight and degradation of material as a function of temperature. This result

is important in providing insight into the original material structure (Wilkie, 1999). TGA thermo

grams were obtained by using a Perkin- Elmer Thermal Analysis system. The curves were

recorded from room temperature to 800ºC at a rate 1°C/min and nitrogen gas as sample purge gas.

Figure 4.3 and 4.4 show the TGA thermogram of glasses LG3 and LG66 respectively.

100

80
Weight %

60

40

20

0
0 1 00 2 00 3 00 4 00 5 00 6 00 7 00 8 00

Temperature (°C)

Figure 4.3: Thermogram for LG3 glass

100

Weight % 80

60

40

20

0
0 100 200 300 400 500 600 700 800

Temperature (°C)

Figure 4.4: Thermogram for LG66 glass

From both thermogram show the original starting glass composition of LG3 and LG66. Both

glasses haven’t exhibited any decomposition until 800°C. This was happen because the first

stages of decomposition of any glass usually take place at temperature 1000°C and above.

Figure 4.5 and 4.6 show the TGA thermogram of glasses PAA and MMT respectively.

94.1%
100 140.4°C

80 66.3%
316.5°C
Weight %

60

40
15.3%
491.9°C
20

0
100 200 300 400 500 600 700 800

Temperature (°C)

Figure 4.5: Thermogram of PAA

99.98%
100 36.70°C

95

90
Weight %

85
80.28%
80 291.63°C

75

70

65
100 200 300 400 500 600 700 800 900

Temperature (°C)

Figure 4.6: Thermogram of MMT

Figure 4.17 shows the thermogram of PAA. It showed three steps of decomposition occured

during heating PAA from room temperature to 800°C. The first decomposition was at 35-140ºC

with the weight loss of 5.9 wt%. This decomposition supports the decarboxylation reaction in

PAA. Second decomposition was at 195-316ºC with the weight loss of 27.8 wt%. This was

thought to be due to anhydride formation. The third decomposition was at 315-491°C which

corresponded to the polyacrylic anhydride formation. This yielded finding was similar with

Moharram and Khafagi (2006).

Figure 4.18 shows the thermogram of MMT. It clearly showed one step of decomposition during

heating MMT from room temperature to 800°C.there was no significant decomposition occurred.

This could be due to the major decomposition of MMT took place at temperature higher than

800ºC. This single decomposition took place at 36-291°C. The weight loss was about 19.7%

corresponded to the loss of free water.

Figure 4.7 and 4.8 show the thermograms of both cements without MMT addition. The patterns

of decomposition for both cements were similar to each other. However, the temperatures and

weight loss percentage were slightly different. For LG3 cement, it initially decomposed at

temperature of 49°C whereas LG66 cement at temperature of 63.52°C. Same situation happened

at high temperature. Both thermograms show two major decompositions. First, it was due to the

water contains that produced during setting which at range 49-151°C. Second, it was due to PAA

that involve in the reaction which at range 401-508°C. It may be due to the similarity of the

glasses. The only difference in these two glasses was the presence of Na2O in LG66 glass.

Therefore, both of glasses showed similar decomposition.

Figures 4.9 and 4.10 show the thermograms of cements with addition of MMT. Both cements

undergo almost similar decomposition. The temperature and percentage of decomposition at

certain stage did not change significantly. Similarly, thermograms still showed two major

decompositions as cement without addition of MMT. This situation might be due to the little

amount of MMT in the cement formulation (2.5 wt% of glass powder and PAA) which actually

did not influence the thermal properties of the cement formed.

110
99.80%
49.00°C
100

90
Weight, %

80.45%
401.73°C
87.31%
80
139.16°C

70

65.63%
60 504.54°C

50
100 200 300 400 500 600 700 800

Temperature, °C

Figure 4.7: Thermogram of LG3 glass without addition of MMT

110

98.01%
100 63.52°C

90
Weight, %

78.39%
85.11%
80 402.35°C
151.15°
C

70

60 63.30%
507.59°C

50
100 200 300 400 500 600 700 800

Temperature, °C

Figure 4.8: Thermogram of LG66 glass without addition of MMT

110
99.79%
46.00°C
100

90
Weight, %

77.85%
84.43% 406.16°C
80 144.58°C

70

60 63.03%
509.60°C

50
100 200 300 400 500 600 700

Temperature, °C

Figure 4.9: Thermogram of LG3 glass with addition of MMT

110
99.52%
45.77°C
100

90
Weight, %

78.39%
85.25% 402.98°C
80
149.60°C

70

60 63.71%
506.27°C

50
100 200 300 400 500 600 700

Temperature, °C

Figure 4.10: Thermogram of LG66 glass with addition of MMT

4.3 Compressive strength of GPCs

Compressive strength of GPCs is due to the maturing and hardening reaction. The invariant

strengths are very dependent on the aging time. Many literatures state that the compressive

strength was increase with longer aging time. The compressive fracture strength calculated using

the formula such below;

P = 4F
2

The unit is MPa. F is the load at fracture force in Newton (N) and D is the average diameter of

the specimen in millimeters (mm).

It is well known that GPCs increase in strengths in water with time due to constant salt-bridge

formations (Wilson and McLean, 1988). This investigation examined the effect of aging on the

compressive strength of glass cement without and with the addition of MMT. On the whole, both

cements gave a sharp increase of compressive strength as time elapse. It was due to the

hardening reaction that took place allow the water uptake for hydrates to fill up the porosity of

the cement to yield high strength of cement (Lea, 1970).

In this study, compressive strengths for both GPCs were determined within 4 time interval at

aging time: 1 day, 7 days, 14 days and 28 days. The compressive strengths of the GPCs from

LG3 cements and LG66 cements without and with addition of MMT as a function of time are

shown in the Table 1 and Table 2. The increases of compressive strengths are clearly shown on

Figure 4.13 and 4.14.

Figure 4.13, the compressive strength of LG3 cements increased rapidly in 14 days period.

Without addition of MMT, LG3 cements can achieve maximum strength up to 53.55 MPa while

with addition of MMT the maximum strength achieved 74.21 MPa. Figure 4.14, the compressive

strength increased slowly between 1 to 7 days aging time. However, rapid increase of

compressive strength happens after 7 days and continued even after 28 days aging time. Without

addition of MMT, LG66 cements can achieve maximum strength up to 53.24 MPa while with

addition of MMT the maximum strength achieved 66.16 MPa. The maximum compressive

strength of LG66 cements was slightly lower than LG3 cements that were 66.16 and 74.21 MPa

respectively.

Table 4.1: Compressive strength of LG3 cement as a function of time

Setting aging time LG3 cement without LG3 cement with Strength increment
MMT MMT %
1 day 38.86 42.6 8.78
7 days 51.61 66.32 22.18
14 days 52.55 74.21 29.19
28 days 53.55 64.16 16.54

Table 4.2: Compressive strength of LG66 cement as a function of time

Setting aging time LG66 cement without LG66 cement with Strength increment
MMT MMT %
1 day 10.38 25.15 58.73
7 days 19.81 51.61 61.62
14 days 37.00 52.55 29.59
28 days 53.24 66.16 19.53

80

With MMT
Compressive Strength, MPa

70 Without MMT

60

50

40

30
0 5 10 15 20 25 30

Aging Time, Day

Figure 4.13: Compressive strength of LG3 cement without and with addition of MMT

80

70
Compressive Strength, MPa

60

50

40

30

20

10

0
0 5 10 15 20 25 30

Aging Time, Day

Figure 4.14: Compressive strength of LG66 cement without and with addition of MMT

This study found that the addition of MMT to the GPCs increased the compressive value and

enhanced the mechanical properties as well. It was due to the property of MMT itself that able to

act as filler by intercalation reaction and fill in the layer within GPCs. The hydrogen bond that

formed between acid and MMT layer also may influence the increase of strength of the GPCs.

According to Drowling et al. (2006), the formation of hydrogen bond occurred between

carboxylic acid group and amine group of ADA-MMT have a greater reinforcing effect on the

mechanical properties of the material system to which they have been added. The amount of

MMT used that is 2.5 wt% also suitable for both glasses in cements formation. Drowling et al.

(2006) highlighted that MMT addition with excess of 2.5 wt% cause in difficulty to mix with the

glass.

The composition of glass strongly influences the interaction in the cement. The 4.4 mole% of

Na2O might cause the differences interaction in the LG66 cements formation. Small quantities of

sodium in the glass composition have a disproportionate influence on cement properties and may

affect compressive strength (De Barra and Hill, 1998). When comparing the trends of

compressive strength for both cements, it was found that LG3 cements showed rapid increase

within 14 days. After 14 days, the compressive strength became slightly lower. For LG66

cements, the compressive strength continually increases even after 28 days. It shows that the

setting reaction of LG3 cements were faster than LG66 cements. This situation most likely

related to the alkali metal anions leaching process. The presence of sodium in LG66 cements

influence the setting reaction and the dissolution chemistry. Sodium ions have tendency to

slower the setting reaction by competes with major interchange crosslinks such calcium and

aluminium cations to bind with carboxylate group of PAA. At initial period of aging time,

sodium may disrupt the crosslinking in the polysalt matrix by delaying the crosslinking of metal

cations (Al3+ and Ca2+) with carboxylate group. This causes the calcium and aluminium cations

unable to crosslink with the carboxylate group. However, this situation only temporary and take

place at early stage of reaction. Sodium has mobile properties to move freely and have tendency

to leave the carboxylate group (Akinmade and Hill, 1991). Therefore, after sodium released from

carboxylate group, calcium and aluminium cations will be available and replace the crosslink and

influence the compressive strength. Similar finding was obtained by De Barra and Hill (1998). In

their study, they found that the influence of sodium content glasses give significant reduction in

compressive strength at early stage of reaction and became considerably reduced as aging time

increase.

Both cements exhibit different value in compressive strength at certain aging time. The

hydrolytic instability may rise in silicate structure for LG66 cement rather than LG3 cement.

According to De Barra and Hill (1998), sodium content glasses would be expected to promote

hydraulic instability in the cement. In GPC formation, it showed that aluminium is the primary

component that contributing the strength of GPC. The sufficient aluminium ion that able to

crosslink gives effect to the full crosslinking (Leon et al., 2007).

In other case, the compressive strength of LG66 cement is too weak without MMT as filler.

From the observation, the surface of this glass cement was virtually wet and too soft at early time

after mixing. However, it becomes slightly hard as time elapse. Again, this situation was due to

the composition of the glass. Sodium obviously affected the working and setting time of the

cements. Despite from this, LG66 glass cement could reach almost the same value of

compressive strength at 28 days aging time. This might be due to the degree of crosslinking for

both cement almost same at this aging time.

The result of mechanical strength demonstrates both of these experimental cements have

potential to be used in application of dental restorative. However other properties such wear

resistance, hardness, dimensional stability and flexural strength should be considered as well.

4.4 Study on setting reaction of GPCs by using FTIR Spectroscopy

Figure 4.13, 4.14 and 4.15 shows the infrared spectra of LG3, LG66 and PAA respectively.

100

80
% Intensity

60

Si-O (Si)
40
Stretch
20

0
4000 3500 3000 2500 2000 1500 1000 500

Wavenumber, cm-1

Figure 4.13: Infrared spectrum for LG3 glass

100

80
% Intensity

60

40 Si-O (Si)
Stretch
20

0
4000 3500 3000 2500 2000 1500 1000 500

1
Wavenumber, cm-

Figure 4.14: Infrared spectrum for LG66 glass

100

80
% Intensity

60

40

O-H
COOH
20

0
4000 3500 3000 2500 2000 1500 1000 500

Wavenumber, cm-1

Figure 4.15: Infrared spectrum for polyacrylic acid, PAA

Figure 4.13 and 4.14 show major absorption band between 1050 – 980 cm-1 that provide

information about the presence of asymmetric Si-O(Si) stretch vibration in the glass. This bond

is the major bond in the glass network. The minor absorption bands develop at lower frequencies

is not really important but it can become some evidences to support the other compound that

present on glass composition. Such, band intensity near 730 cm-1 are may related to the Al, Ca

and/or ions from the silica network. Band between 850 – 500 cm-1 due to extraneous ion such

Ca2+ and Na+ that incorporated in glass phase (Farmer et al., 1979). Even though LG66 glass

have slightly different composition with LG3 glass, but these spectrum were still unable to

confirm the differences. As observed, glass spectra have almost no important band at frequency

above 1250 cm-1.

In Figure 4.15, strong band with medium width occurred in the region 1700 – 1660 cm-1 displays

peaks attributed to the C=O stretching vibration. The broad absorption near 3200 cm-1 to 2400

cm-1 gives information of acidity character. This stretch peak was very broad due to hydrogen

bond in PAA.

4.4.1 Setting reaction of GPCs without MMT addition

GPC formation involves acid base neutralization reaction. Acid come from aqueous PAA while

base come from aluminosilicate glass. It also known as water base reaction since water took part

as the medium of the reaction. The reaction initiated by the reduction of metallic ions from the

glass and causes siliceous hydrogel layers form on the surface of the glass. Associated with the

continuous reaction, the metal ions crosslink with the conjugated base of the acid and result

hardening and maturing process. Cross linking of these ions result the formation of a primary

polysalt matrix within the set cement (Matsuya et al., 1996).

The setting reaction of the GPC can be followed by FTIR spectroscopy. Figure 4.16 shows the
IR spectra of LG3 cement without MMT with aging time 5 minutes to 28days.

Figure 4.16: Infrared spectra of LG3 cement without MMT addition with aging time from
5 minutes to 28 days

Figure 4.16 showed the noticeable change pattern of infrared spectra for LG3 glass and its

cements. For original glass, there was only one absorption peak between 1050 – 980 cm-1. After

5 minutes aging time, two new peaks already developed. The peak appeared between 1710 –

1390 cm-1. The appearance of this peak was due to the formation of COO-M+ from the cross

linking of metal ions with carboxylate group. Another peak present as a shoulder at previous

asymmetric Si-O(Si) stretch of original glass. This peak at region 900 cm-1 corresponds to the

formation of hydrated silica gel (Si-OH). The change of absorption pattern between 1200 – 900

cm-1 were related to the evaluation of band as cement formed (Matsuya et al., 1984, 1996). The

stretching vibration observed at 1650 cm-1 due to the binding vibration water that appeared after

the leaching (Davis and Tomozawa, 1996). Peak at region 3700 to 2400 cm-1 came from O-H

stretch.

As time elapsed, the shoulder peak at 1570 cm-1 became increase in intensity. This was due to

formation COO-M+ became increase as metal ions (Al3+ and Ca2+) crosslink with the carboxyl

group in the acid (Crisp and Wilson, 1974). In contrast, the intensity of shoulder peak at 1710

cm-1 became decrease in intensity. This was because H+ from acid was taken by silica network to

form silica gel layer during the cross linking of metal ions and COO - in cements formation.

Figure 4.17: Infrared spectra of LG66 glass without MMT addition with aging time from 5
minutes to 28 days

Figure 4.17 showed the noticeable change pattern of infrared spectra for LG66 glass and its

cements. For original glass, there was only one absorption peak between 1050 – 980 cm-1.

Generally, the absorption peaks of LG66 cements were similar with LG3 cements. Two new

peaks developed after 5 minutes set of cements. The peak appeared between 1710 – 1400 cm-1.

The appearance of this peak was also due to the formation of COO -M+ from the cross linking of

metal ions with carboxylate group. Another peak present as a shoulder at previous asymmetric

Si-O(Si) stretch of original glass. This peak at region 900 cm-1 corresponded to the formation of

hydrated silica gel (Si-OH). The change of absorption pattern observed between 1200 – 900 cm-1

and the stretching vibration at 1650 cm-1 were also same with LG3 cements. Peak at region 3700

to 2400 cm-1 came from O-H stretch.

As time elapsed, the shoulder peak at 1550 cm-1 became increase in intensity. This was due to

formation COO-M+ became increase due to the cross-linking in the cement matrix (Crisp and

Wilson, 1974). In contrast, the intensity of shoulder peak at 1710 cm-1 became decrease in

intensity. This was because H+ from acid was taken by silica network to form silica gel layer

during the cross linking of metal ions and COO- in cements.

Both infrared spectra showed the most significant changes especially at early stage of reaction.

Setting reaction of LG3 cements is considerably faster than LG66 cements. Both change patterns

can be seen clearly between 5 minutes to 10 minutes. As aging time increases, the patterns

become almost similar. COOH absorption band almost become weak in intensity after 7 days

aging time. This could be due to the fast rate of crosslink of polycarboxylic acid by Ca2+ ion and/

or Al3+ within 7 days and thus reducing the COOH intensity of the acid. New band that indicate

the formation of COO-M+ already appeared at 5 minutes aging time. This situation also

contributed to the gelation of the carboxylate to form hard surface. For both glasses, the intensity

of COOH and COO-M+ peaks remains constant after 7 days. This shows that there are

possibilities that cross-linking between metal ions and conjugated base from acid have been

completed after 7 days setting aging time. During the setting reaction, silica gel and cross-linking

reaction take place simultaneously.

From both figures, it clearly showed that during the setting reaction, the absorption band between

1100 to 900 cm-1 became unnoticeable as aging time increased. This broad peak moved toward

higher frequency with increase of aging time, and finally the band showed a maximum

around1100 cm-1. The formation of hydrated silica gel caused the condensation of Si-OH bond to

form Si-O-Si with around surface of glass being siliceous. The spectral pattern was quite similar

to that of hydrated silica gel that proposed by Hanna and Su (1964). Their finding also obtained

that spectra of GPC had a strong band around 1050 cm-1 due to the Si-O-Si stretching vibration.

This fact also supported by Soda (1961) where a medium band around 950 cm-1 was due to Si-

OH deformation vibration. The intensity of Si-O-Si showed no significant changes after 10

minutes of setting reaction for LG3 cement and 30 minutes of setting reaction for LG66 cement.

It may due to water molecules in glass network were completely eliminated after this desired

aging time. Similar result was reported by Berzins D et al.,(2010). In their study, they found that

the broad peak centered around 1600 cm-1 show that water was the most abundant decomposition

product during the reaction between glass and PAA.

During hardening and maturing stage, metallic ions typically bind to polyanions via carboxylate

groups. The initial cross linking achieved because the more readily available metal ions. Rapid

reaction results the formation of hard surface within few minutes from the start of mixing.

However, the different composition of metallic ion is leading to the difference of the time taken.

LG66 glass contains sodium. According to De Barra and Hill (1998), small quantities of sodium

are likely influence the cement properties. This was because sodium ions have tendency to

compete with other ion like calcium and aluminium cations and inhibit the crosslinking process.

Therefore, the presence of sodium will increase the working time. LG3 cements set more rapidly

compare than LG66 cement due to absence of sodium in LG3 glass. The rate of setting for LG3

cement and LG66 cement were relatively different when compared at early stage of reaction.

From the infrared spectra also, it was clearly showed that the intensity of COO -M+ and COOH

peak significantly different at 5 minutes aging time.

From Figure 4.18, at 5 minutes aging time for LG66 cement, the absorption band that

corresponds to formation of COO-M+ is relatively weak at region 1600 – 1400 cm-1. That might

be due to the delay reaction of cross linking due to the presence of sodium. This is also the main

reason why the working time in this stage is too slow and GPCs formed have low compressive

strength. The development of shoulder peak on asymmetric Si-O(Si) stretch is also observed but

the absorption still very weak. The setting reaction of LG66 cement seemed slower than LG3

cement. It is because even at 10 minutes aging time, the intensity of COO-M+ stretching vibration

still relatively weaker than LG3 glass at the same aging time. As mentioned earlier, this happen

might be due to the sodium ion that acts to delay setting reaction. Sodium ions have tendency to

compete with other ion like calcium and aluminium cations and may inhibit the crosslinking

process.

LG3
Intensity, %

LG66

Wavenumber, cm-1
Figure 4.18: Comparison of FTIR spectra of LG3 cement and LG66 cement without MMT

at 5 minutes aging time

4.4.2 Setting reaction of GPCs with MMT addition

Figure 4.19 shows the spectrum for MMT. MMT showed major broad absorption bands around

1260 cm-1 to 730cm-1 that corresponded to the structural bending mode (Farmer, 1974). Figure

4.20 and 4.21 show FTIR spectra for LG3 and LG66 glass without and with addition of MMT at

5 minutes aging time. A slight difference between spectrum of both cements without MMT and

with MMT was the shoulder peak at 920 cm-1 that corresponded to hydrated silica gel. With

addition of MMT, this peak is seemed hardly to observe. The intensity of this peak was very

small compared with glass without MMT. This may have been because of hardening reaction

that took place. Cements with MMT easily to form hard surface and less working time compare

than cements without MMT.

100

80
% Intensity

60

40

20

0
2000 1800 1600 1400 1200 1000 800

Wavenumber, cm-1

Figure 4.19: Infrared spectrum of MMT

% Intensity

With MMT
Si-O(Si)
Without
Si-O(H)
MMT

2 0 0 0 1 8 0 0 1 6 0 0 1 4 0 0 1 2 0 0 1 0 0 0 8 0 0

Wavelength, cm-1

Figure 4.20: Infrared spectra of LG3 glass with and without addition of MMT at 5 minutes

With MMT
% Intensity

Si-O(Si) Without
Si-O(H)
MMT

2 0 0 0 1 8 0 0 1 6 0 0 1 4 0 0 1 2 0 0 1 0 0 0 8 0 0

Wavelength, cm-1
Figure4.21: Infrared spectra of LG66 glass with and without addition of MMT at

5 minutes
CHAPTER 5

CONCLUSION AND RECOMMENDATION

5.1 Conclusion

The compressive strength for both GPCs were improved with the addition of MMT. For GPCs

from LG3 glass, the maximum compressive strength can be achieved was 74 MPa. Without the

addition of MMT it only can achieve 53 MPa. GPCs from LG66 glass gave maximum

compressive strength 66 MPa with addition of MMT and 53.24 Mpa without addition of MMT.

It proves that MMT able to act as filler by intercalation reaction within GPCs. The formation of

hydrogen bonding also provides the great effect on the compressive strength.

The setting reactions of GPCs were followed by FTIR spectroscopy. For both GPCs, the

absorption band around 1700 cm-1 that represents COOH decreased in intensity. While the

intensity of absorption band around 1540cm-1 that represent COO-M+ peak increased with time.

It was due to the H+ from acid was taken by silica network during the cross linking of metal ions

and COO- crosslink with metal cations in cements formation. The peak located at region 900cm-1

corresponded to the formation hydrated silica gel (Si-OH). In conclusion, the setting reaction of

GPCs from LG3 glass was faster than GPCs from LG66 glass. It was due to the presence of

sodium ion in LG66 glass that disturb the crosslinking process in the cement formation.

5.2 Recommendation

This study has highlighted the use of FTIR technique to study the setting reaction of the GPCs.

However, another technique that equivalent to study this setting reaction also can be used in

order to optimize the finding.

For the future work, the setting reaction can be followed by using MAS-NMR spectroscopy. This

technique enables us to probe the structure of amorphous glasses and determine the molecular

structure. Other than that, the changes in silicate network structure can be observed as the

tetrahedral state, Al(IV) switches to octahedral state, Al(VI).

Another recommendation is to study different type of modified MMT in order to increase the

mechanical strength of the GPCs.

300

200
Intensity (a.u)

100

0
20 30 40 50 60

2-Theta (Deg/°)

XRD pattern for LG3 glass cement without addition of MMT

300

200
Intensity (a.u)

100

0
20 30 40 50 60
2-Theta (Deg/°)

XRD pattern for LG3 glass cement with addition of MMT

3 00

Intensity (a.u)

2 00

1 00

0
20 30 40 50 60

2-Theta (Deg/°)

XRD pattern for LG66 glass cement without addition of MMT

300

Intensity (a.u)

200

100

0
20 30 40 50 60
2-Theta (Deg/°)

XRD pattern for LG66 glass cement with addition of MMT

APPENDICES-C

COMPRESSIVE STRENGTH TABLES

1 day 7 days 14 days 28 days
40.48 50.21 52.25 58.32
37.98 55.44 51.37 51.13
31.23 50.61 53.68 53.37
45.76 50.17 52.48 50.17
38.85 51.62 52.97 54.76

38.86 51.61 52.55 53.55
Compressive strength of LG3 glass without addition of MMT

Compressive strength of LG3 glass with addition of MMT

39.78 70.62 77.51035 69.50
44.97 71.82 65.33787 63.27
45.42 64.15 71.17567 64.86
47.48 66.91 75.60180 61.72
35.35 58.10 72.42 61.48

42.60 66.32 72.41 64.16

Compressive strength of LG66 glass without addition of MMT

10.39 30.03 39.43 55.28
9.72 18.23 37.44 52.16
11.74 21.68 38.54 50.60
9.34 15.33 32.60 54.90
10.71 13.80 36.99 53.26

10.38 19.81 37.00 53.24

Compressive strength of LG66 glass with addition of MMT

24.78 50.21 52.25 68.39314
23.68 55.44 51.37 61.18370
23.56 50.61 53.68 64.40073
26.98 50.17 52.48 47.58641
26.75 51.62 52.97 70.67623

25.15 51.61 52.55 66.16

100

80

60
Intensity,%

40

20

0
4000 3500 3000 2500 2000 1500 1000 500

Wavenumber, cm-1

LG3 glass without addition of MMT at 5 minutes setting reaction

100

80

60
Intensity,%

40

20

0
4000 3500 3000 2500 2000 1500 1000 500

Wavenumber, cm-1

LG3 glass without addition of MMT at 28 days setting reaction

100

80

60
Intensity,%

40

20

0
4000 3500 3000 2500 2000 1500 1000 500

Wavenumber, cm-1

LG66 glass without addition of MMT at 5 minutes setting reaction

100

80
Intensity,%

60

40

20

0
4000 3500 3000 2500 2000 1500 1000 500

Wavenumber, cm-1

LG66 glass with addition of MMT at 28 days setting reaction

100

80

60
Intensity,%

40

20

0
4000 3500 3000 2500 2000 1500 1000 500

Wavenumber, cm-1

LG3 glass

100

80
Intensity,%

60

40

20

0
40 0 0 35 0 0 30 0 0 25 0 0 20 0 0 15 0 0 10 0 0 5 00

Wavenumber, cm-1

LG66 glass

100

80

60
Intensity,%

40

20

0
4000 3500 3000 2500 2000 1500 1000 500

Wavenumber, cm-1

PAA

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