1. Mechanical Engineering Technology
Reusable Bottles Materials
Name of Principal Author: Stephanie Ulman
210.01-04 Materials in Engineering Design
Project
Date of Submission:
November 20, 2013
Abstract:
Reusable bottles have always been around since the 1700s but, they have not been popular
until today. Today, they are made out of two materials that are BPA free, have high resistance
to chemicals (such as water and electrolytes), must be rigid, must be able to withstand cold
temperatures (preferably around -18°C to 0°C), have a high melting temperature (around 120°C
to 150°C) and must be resistant to absorb water. The user of the bottle must be able to clean
out the bottle after using it. One of the most popular company of a reusable bottle is Nalgene.
The materials HDPE and PP are used in the reusable bottle because they fit in these
requirements in order for the product to reusable. Today, scientists are trying to make plastic
products be more environmentally friendly, because most plastic products end up in landfills
and they do not break down. According to research the best biodegradable material for a
reusable bottle would be bio-PET.

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Introduction:
In the 1600’s, leather skins from animals were used to carry water. Of course, this had some
major problems such as it was not clean inside, it leaked, and they had a funny taste and smell.
In the 1700’s in America glass bottles were used. It was very expensive to make so people had a
scarce amount of them. Glass reusable bottles were used for soda, beer, milk and medicine.
People reused their bottles by taking them back to the stores because owners would give
money them if they would reuse their bottle. An advantage of having glass bottles milk says
cooler longer and does not spoil as fast. A disadvantage of glass bottles is that they can break
very easily.
In the 1800’s, people started to use metal canteens because they did not break. Metal
canteens had drawbacks as well. Metal canteens had a small opening so it was hard to fill and
it was impossible to clean. Another disadvantage of metal canteens it gave the water a weird
taste. When the temperature was below freezing outside, people drank from their water
canteen and it would stick to their lip.
People used metal canteens until the 1970’s, then polyethylene bottles became popular.
Polyethylene bottles had many advantages such as they are lightweight, does not give the
water a metallic taste, and they do not break. Polyethylene bottles were developed in 1949 by
Emanuel Goldberg. These bottles were used to hold chemicals in the lab. Later, scientists
brought their lab bottles to store things in while they went camping because the bottle was
perfect to store things in. In the1970’s, the Nalgene bottles were added to the camping
equipment in stores.
Currently plastic bottles are really popular they are made out of various types of plastic, colors
and shapes. In 2006, there was a BPA scare were people found out some plastic bottles
contained BPA (bisphenol A) which is an industrial chemical that is found in some plastics. It is
found in polycarbonate and its epoxy resins. Some of the applications of BPA are cell phones
computers, eyeglasses, drinking bottles, medical devices, food containers, and CDs. BPA is bad
for human body. Research states BPA can cause hormone levels to increase, brain and behavior
problems, cancer, heart problems, obesity, and diabetes. This is a good reason to check the
label when buying a product to make sure it is BPA free.
Today, Nalgene makes several products such as containers, travel kits, cups, and a variety kind
of bottles. Nalgene products are made of the materials mainly copolyester, HDPE, LDPE,
Polypropylene (PP) Polyethylene terephthalate (PET), and stainless steel.
The product that was chosen is a 16 ounce narrow mouth bottle by Nalgene shown in Figure 1
below. The 16 ounce narrow mouth bottle has many design requirements that have to be met.
This product must be BPA free. The threads of the bottle have to be straight shouldered semi-
buttress threads for a greater surface. So the bottle can be tightened with a greater force. The

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cap must be durable and has to mate perfectly with the bottle in order for the bottle not to
leak. Another design requirement is that the bottle must be durable and thick for it to be more
resistant to impact failure. The bottom of the bottle is must be round in order for it to be easier
to clean.
Figure 1 shows the N Nalgene 16 ounce bottle.
Discussion:
High Density Polyethylene
The material of bottle is made out of High Density polyethylene (HDPE). The bottle is processed
by blow molding. HDPE is type of polyethylene that has a higher molecular weight than other
polyethylene materials. The chain of HDPE is located in figure 2. The repeat unit of HDPE is in
figure 2 as well. According to CES (general propose molding extrusion), HDPE repeat unit is
between 10,000-20,000. The molecular weight of the repeat unit of HDPE is 28.02g/mol.
Figure 2 shows the chain of HDPE on the left and it shows the repeat unit on the right.
HDPE is a thermoplastic and they have covalent bonds in the chains that make up the material
HDPE. Thermoplastics can be re-melted over and over without destroying the covalent bonds in
the structure. Thermoplastics have covalent bonds in the chain. HDPE is a homo-polymer which
means the monomer repeats itself shown in figure 1. The convent bonds make a linear
Cap
Bottle

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structure which means that the material has a more crystalline structure. A more crystalline
structure has are more organized and as closely packed together.
Some other applications of HDPE is that (CES) are pipes, toys, bowls, buckets, milk bottles,
crates, tanks, containers, film packaging, and blown bottles for food.
HDPE has many great properties about the material. The tensile strength of the material is 22.1
to 31 MPa according to Table 1. (CES) This means that HDPE has good strength and is rigid.
Good strength means that the bonds the interior forces are better holding the material
together. The linear structure and the crystalline of the HDPE make it a high tensile strength as
well.
The density of the material is also important because the higher the density the more strength
that the material will have. The density of HDPE is located in Table 1. The density can range
between 952 and 965 (kg/m^3). (CES) The actual resin density of the material is 950 (kg/m^3)
(or 0.95 specify gravity). (Thermo Scientific) Table 2)
Properties of HDPE
Tensile strength
(MPa)
22.1 - 31
Density (kg/m^3) 952 -965
Water absorption at
24 hrs. (%)
0.005-0.01
Melting point (C) 130-137
Glass temperature
(C)
-125 - -90
Transparency Translucent
Table 1 shows properties of HDPE from CES general purpose, molding & extrusion (level 3)
The temperature ranges are very important for a water bottle because people use them to
drink out of. There glass temperature ranges from the table above -125°C to -90 °C. Nalgene
makes the bottle have the glass temperature of the bottle at -25°C. The glass temperature is
really cold temperatures so the water bottle can undergo freezer temperatures. If the customer
wants to freeze whatever liquid they put in the bottle they can.
The melting point is also important because that is the state when the plastic starts to melt. It is
important that the water bottle does not melt. According to Table 1 (CES) the melting point is

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between 130°C and 137°C. From Table 3 (Thermo Scientific) the melting point is between 125°C
and 138°C.
A small water absorption needs to a property of the material as well. Table 1 (CES) shows the
water absorption that can happen in 24 hours. HDPE can absorb between 0.005% and 0.01%
water in 24 hours. Thermo Scientific water absorption is less than 0.02%.
The bottle is translucent so people will be able to see how much liquid is in there bottle.
Table 2 shows the properties of the plastic resin that is used for the Nalgene water bottle. (From
the Thermo Scientific Nalgene Bottles and Carboys)
Table 3 shows the properties of the plastic resin that is used for the Nalgene water bottle. (From
the Thermo Scientific Nalgene Bottles and Carboys)
According to Appendix 1 (Nalgene) and Appendix 2 (CES), HDPE has an excellent chemistry
resistance for both water and fluid with electro-lights such as juices, sodas, and Gatorade. This
is good to know because the customer will drink these fluids and know that the bottle can
tolerate water and fluid with electro-lights.
HDPE can be recycled it is a number 2 on the recycling chart. Meaning it can be broken down
easily. HDPE has poor UV resistance as well. HDPE is not biodegradable.
According to POLYETHYLENE, HDPE has a low impact strength which ranges from 0.5-20ft-lib/in.
A low impact strength is good because the user does not want the bottle to break or have a
mark on it if the user drops it.

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Polypropylene
The cap of the bottle is made out of PP. The chain of Polypropylene (PP) and the repeat unit is
located in figure 3. The molecular weight of the repeat unit is 42.08 g/mol.
Figure 3 shows a repeat unit of PP.
Figure 4 shows a chain of syndiotactic PP.
Figure 4 shows an isotactic PP. The red is carbon atom while the blue is hydrogen.
PP is a thermoplastic and they also have covalent bonds in the chains. PP is co-polymer because
it has two different monomers in the chain. There are two different types of tacticities an
isotactic or a syndiotactic tacticity. An isotactic tacticity of PP is shown in figure 5. Figure 5
shows all the methyl groups are on the same side. Figure 4 shows the syndiotactic tacticity
methyl groups are alternating sides.
The research shows that the cap of the bottle has an isotactic tacticity. Isotactic tacticity are
less branched and is easier to crystalize than syndiotactic tacticity. This means that isotactic
tacticity is less branched than syndiotacity. Therefore, syndiotactic PP is softer than isotactic PP.
Isotactic PP is more rigid and has better crack resistance. Since PP are co-polymers and have
two monomers that are repeating each other it will be more branched and less crystalline than
HDPE.
PP is have many another applications such as ropes, general polymer engineering, automobile
air ducting, parcel shelving, and air-cleaners, garden furniture, washing machine tank, wet-cell

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battery cases, pipes and pipe fittings, beer bottle crates, chair shells, capacitor dielectrics, cable
insulation, kitchen kettles, car bumpers, shatter proof glasses, crates, suitcases, artificial turf,
and thermal underwear. (CES level 2)
PP tensile strength of the material is between 27.6 and 41.4 MPa. (Table 4 CES) This means it
has good strength and is rigid. This means that PP crystalline structure is rigid and the interior
forces are holding them together.
According to CES that the density is slightly less than the HDPE as it ranges between 890 and
910 (kg/m^3). Also Nalgene shows it is less than HDPE giving it a density of 900 kg/m^3. (0.9
specific gravity) This means it is slightly less strong than HDPE.
Properties of PP
Tensile strength
(MPa)
27.6-41.4
Density (kg/m^3) 890-910
Melting point (C) 150-175
Glass temperature
(C)
-25.2 - -15.2
Transparency Translucent
Table 6 shows the properties of PP from CES (level 2)
The glass temperature ranges from -25.2°C - -15.2°C (Table 4) Nalgene shows the glass
temperature to be between -20°C to -5°C. (Table 3) This is good range. The average freezer
temperature ranges to -18°C to 0°C, so customers can freeze there water not worry about their
bottle cracking.
The melting point of PP can range between 150°C to 175°C. (table 6) The data that Nalgene
shows is that the melting point is between 160°C and 176°C. (Table 3) This is essential because
the melting point has to higher than outside temperatures. PP has a higher melting
temperature than HDPE.
PP has excellent resistance to water absorption. The water absorption is less than 0.02%. (Table
3)
According to Nalgene PP is the best stress-crack resistance of the polyolefins. This is good
because it is the cap of the bottle and the user is frequently twisting the cap on and off the
bottle.

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The cap also has poor impact-resistant and may crack or break when dropped from bench-top
height. (Nalgene) PP also has excellent resistance towards water and fluids with electro-lights.
(Appendix 1) The cap of the bottle is made by injection molding. PP has poor creep resistance
and poor UV resistance. PP can be recycled as it is numbered 4 on the recycling chart, meaning
it can not be broken down as easily as HDPE can. PP is not biodegradable as well.
Green polymer
Globally scientists are trying to figure out a way to make polymers more environmentally
friendly. Most polymers end up in the landfill including reusable bottles.
Today scientists are trying to make biogradable polymers and biopolymers so they can be
broken down. Biopolymers are biodegradable and some are compostable as well.
Biodegradable polymers are naturally occurring in nature. Meaning that they can be broken
down into CO2, methane, water, inorganic compounds or bimass by microorganisms. A
compostable polymer can be broken down into CO2, methane, water, inorganic compounds and
bimass in an amount of time and high temperatures.
From research that best biopolymer for reusable bottles are bio-ppolyethylene terephthalate
(PET). BioPET is used for many different products today such as shampoo bottles, Heinz ketchup
bottles, and coke bottles.
These bio-PET bottles used today are not all bioplastic. Meaning, 30% of the bottle is made out
of ethylene glycol made from sugar cane and 70% is PET. Pepsico made the first bio-PET bottle
that was 100% bio-based. The product is still in the lab today and not being used yet. They are
made out of switch grass, pine bark, and corn husks. Pepsi wants to use orange and potato
peels in the future for food products.
Some of the properties of bio-PET they and rigid and they have poor barrier properties again
(CO2, H20 and O2) under industrial composting conditions. When bio-PET bottles are put into
glass transition temperatures, the bottle is undergo creep and plasticity. One of the bio-PET
name that is the closest properties HDPE and PP in Nalgene bottles is PTI 002. The glass
temperature of PTI 002 is 78 C. Syntex did not show the melting temperature, but it showed the
mixing temperature which is 248 C. Since bio-PET bottles are used for coke bottles an
assumption is that bio-PET is a good material for reusable bottles.

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Conclusion:
In conclusion, the reusable bottle must be BPA free, have high resistance to chemicals (such as
water and electrolytes), must be rigid, must be able to withstand cold temperatures (preferably
around -18°C to 0°C), have a high melting temperature (around 120°C to 150°C) and must be
resistant to absorb water. The materials used in Nalgene bottles are HDPE and PP, because they
fit in these requirements. These properties are very important to have in a reusable bottle. The
closest biopolymer that met these requirements is bio-PET. This biopolymer is used for some
applications today. Hopefully in the future, scientists can make biopolymers in most products
that are used today.

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Appendix 1:
This appendix shows the Chemical Resistance of the 16 ounce bottle from Nalgene.
Chemical Resistance Classification
E: 30 days of constant exposure causes no damage. Plastic may even tolerate for years.
G: Little or no damage after 30 days of constant exposure to the reagent.
F: Some effect after 7 days of constant exposure to the reagent. Depending on the plastic, the
effect may be crazing, cracking, loss of strength or discoloration. Solvents may cause softening,
swelling and permeation losses with LDPE, HDPE, PP, PPCO and PMP. The solvent effects on
these five resins are normally reversible; the part will usually return to its normal condition
after evaporation.
N: Not recommended for continuous use. Immediate damage may occur. Depending on the
plastic, the effect will be a more severe crazing, cracking, loss of strength, discoloration,
deformation, dissolution or permeation loss.

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Appendix 2
This table shows the CES data for HDPE
Water
(fresh) Excellent
Water (salt) Excellent
Weak acids Excellent
Strong acids Acceptable
Weak alkalis Excellent
Strong alkalis Excellent
Organic
solvents Limited use
UV radiation
(sunlight) Fair
Oxidation at
500C Unacceptable
Recyclable Yes
Biodegrade No

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