polystyrene preparation , properties , applications

2. POLYSTYRENE
(POLY VINYL BENZENE)
SPECIFICATIONS COPOLYMERS
 Low cost
 higher weight
 good electrical properties
 good mould ability
 excellent color range
 transparency
 rigidity
 low water absorption
 High Impact Polystyrene
(HIPS)
 Styrene acrylo nitrile (SAN)
 Acrylonitrile Butadiene
Styrene (ABS)

3. MONOMER PREPARATION
benzene + ethane ethyl benzene
Ethyl benzene styrene

4. MANUFACTURING
1. Mass polymerization
• Gives polymers of high clarity/electrical resistance
• Styrene monomer is heated @ 800c for 2 days till 33%-35%
polymerization occurs
• The whole mixture is run out in to a tower about 25 feet
height
• Temp. in tower
top= 1100c middle= 1500c
bottom= 1800c (boiled off residual monomers)
• Cooled and disintegrated and packed

6. 2 . Solution polymerization
 Styrene and solvent blended together and pumped
through number of reactors
 Solvent and polymer fed in to extruder
 Extrudated , granulated and stored
 Residual monomers and very low molecular weight
polymers are removed

8. 3. Suspension polymerization
 Monomer suspended in droplets
 Use soluble initiator like BPO
 Coat the droplets using suspension agents like PVA
 Polymerization takes place, unreacted monomers removed

9. GENERAL PROPERTIES
 specific gravity - 1.05
 tensile strength - 32.4-56.5 MPa
 tensile modulus - 3103-3276 Mpa
 flexural modulus - 3103-3448 Mpa
 elongation at break - 1.2-3.6 %
 Impact strength - 13.3-24 J/m
 hardness - M 60-84
 Glass transition temp.- 74-1100c
 dielectric strength - 19.7 KV/mm

10. PROCESSING TECHNIQUES
INJECTION MOLDING
Melts are medium viscous
GPPS(general purpose PS)
wall thickness – 150:1
processing temp - 200-2500c
HIPS(high molecular weight PS)
wall thickness - 130:1
Processing temp – 180*250*c
Injection pressure - 30-275Mpa

11. EXTRUSION
 Used for making sheets used in thermoforms.
 Screw L/D ratio – 25:1 to 30:1
 Compression ratio – 2:1 to 3:1
 Processing temp – 150* - 250*c
THERMOFORMING
 Forming temp 130* - 180*c
 Removal temp 85*c

12. PROCESSING CONSIDERATIONS
• The negligible water absorption avoids the need of
pre-drying
• Specific heat of PS is less, therefore higher
plasticizing machines should be used
• Due to amorphous in nature, polymer gives low
mould shrinkage
 The strong dependence of apparent viscosity or shear
rate .this necessities particular care in the designers
complex extrusion dies

13. APPLICATIONS
HOUSEHOLD AUTOMOTIVE
 Power boxes
 Combs
 Toys
 Bangles
 Decorative gift articles
 Ball pen
 Water jug
 Mugs
 Plates
 Reflector
 Doom light
 Display signs
 Automotive penal covers

14. ELECTRICAL &ETRONICS MEDICAL
 Light diffusers
 Battery case
 Electrical coil forms
 TV and transistor cabinets
 Refrigerator
 Door and body liners
 Floppy storage boxes
 Disposable syringe

15. PACKAGING INDUSTRIAL
 Thin walled packaging
 Containers
 Bottles
 Fish packaging
 Flower packaging
 Bottle caps
 Battery case
 Filling cabinets
 Blade dispenser
CONSTRUCTION
 Toilet seats
 Wall tiles
 Towel racks
 Window envelope

16. REFERENCE
 PLASTIC MATERIALS
-CIPET
• PLASTIC MATERIALS
-BRYDSON.JA
 Working with Polystyrene
-Bill Fry