Polymers

Question 1

What are the three types of polymers?

Answer 1

Thermoplastics, thermosetting plastics and elastomers.

Question 2

What are the properties of thermoplastics?

Answer 2

-has ‘plastic memory’
-melts at relatively lower temperatures
-not appropriate in a heat-related setting
-widely used and recycled

Question 3

Give examples of thermoplastics.

Answer 3

-Low-density polyethylene (LDPE)
-Acrylonitrile butadiene styrene (ABS)
-Nylon
-High-impact polystyrene (HIPS)
-High-density polyethylene (HDPE)
-Acrylic/polymethylmethacrylate (PMMA)
-Polypropylene (PP)
-Polyvinyl-chloride (PVC)
-Unplasticised polyvinyl-chloride (uPVC)
-Polyethylene terephthalate (PET)
-Polystyrene (PS)

Question 4

What are the properties of thermosetting plastics?

Answer 4

-permanent shape
-high heat resistance (will burn if heated)
-non-recyclable

Question 5

Give examples of thermosetting plastics.

Answer 5

-Polyester resin
-Melamine formaldehyde
-Urea formaldehyde (UF)
-Epoxy resin

Question 6

What are the properties of elastomers?

Answer 6

-good elasticity
-can be distorted under pressure and return to its original shape

Question 7

Give examples of elastomers.

Answer 7

-Natural rubber (Polyisoprene)
-Butadiene rubber (BR)
-Neoprene (Polychloroprene rubber)
-silicone

Question 8

What are the performance characteristics of polymers?

Answer 8

-toughness
-elasticity
-insulation (thermal and electricity)
-UV resistance
-ability to be moulded
-chemical and liquid resistance
-melting point
-suitability for food applications
-biodegradability
-self-finishing
-ability to be combined with polymers and additives

Question 9

What are polymer enhancements?

Answer 9

Polymer enhancements are additives added into polymers to improve certain characteristics and properties.

Question 10

What do lubricants do?

Answer 10

Lubricants, wax or calcium stearate, reduce the viscosity of the molten polymer which allows for more intricate shapes to be formed. It also lowers the moulding temperature, thus saving energy.

Question 11

What do thermal antioxidants do?

Answer 11

Thermal antioxidants help prevent the polymer from oxidising or discolouring due to excessive heat during processing.

Question 12

What do pigments do?

Answer 12

Pigments are tiny particles that are mixed into the polymer in its molten state to give colour to the final processed product.

Question 13

What do antistatics do?

Answer 13

Antistatics improve surface conductivity by attracting moisture from the surroundings, therefore reducing static charge.

Question 14

What do flame retardants do?

Answer 14

Flame retardants reduce the likelihood of combustion or the spread of fire.

Question 15

What do plasticisers do?

Answer 15

Plasticisers allow plastics such as PVC to become less hard and brittle at normal temperatures, or LDPE in the manufacture of food wrap, allowing the wrap to be stretched. It also helps in processing because they allow polymers to be easily formed at higher temperatures.

Question 16

What do fillers do?

Answer 16

Fillers can provide reinforcement to the polymer, reduce costs by using less expensive components and increasing product volume or weight.

Question 17

What do antioxidants do?

Answer 17

Antioxidants help reduce the environmental deterioration of the polymer due to exposure from oxygen in the air.

Question 18

What do UV light stabilisers do?

Answer 18

UV light stabilisers prevent the polymer chains from breaking down by sunlight and discolouration.

Question 19

What are the performance characteristics of polymers?

Answer 19

• toughness
• elasticity
• insulation (thermal and electrical)
• UV resistance
• ability to be moulded
• chemical and liquid resistance
• melting points
• suitability for food packaging applications
• biodegradability
• recyclability
• self-finishing
• ability to be combined with polymers and additives

Question 20

What are biodegradable polymers?

Answer 20

Biopolymers are polymers that are designed to degrade in as little as a few months to a couple of years.
Degradation occurs in the presence of: light, water, oxygen.
Natural biopolymers are made from natural materials such as cellulose starch and polysaccharides.
Synthetic biopolymers are made from renewable resources bet are chemically engineered (synthesised) to break down more quickly.

Question 21

What are the polymer stock forms?

Answer 21

• powder
• granules
• sheets
• film
• rods
• foam

Question 22

What are the polymer processes?

Answer 22

-vacuum forming
-thermoforming
-line bending
-laminating (layup)
-injection moulding
-blow moulding
-rotational moulding
-extrusion moulding
-compression moulding

Question 23

What are the moulding processes?

Answer 23

Thermoplastic
-injection moulding
-blow moulding
-rotational moudling
-extrusion
-calendaring

Thermoset
-compression moulding

Question 24

What are the forming processes?

Answer 24

Thermoplastic
-vacuum forming
-thermoforming
-line bending

Question 25

What are the joining processes?

Answer 25

Thermoplastic
-screw fixings
-integral snap fixing
-captive nuts
-adhesives
-thermal welding
-ultrasonic welding

Thermoset
-screw fixings
-adhesives

Question 26

What is vacuum forming?

Answer 26

Vacuum forming is a process that shapes heated plastic sheets over a mold using vacuum pressure.

Question 26

What is vacuum forming used for?

Answer 26

Vacuum forming is used to make prototypes, packaging, automotive parts, industrial components, custom items, displays, signs, and medical device parts.