Exam Style Questions: Performance Characteristics of Polymers, Biodegradable Polymers, Polymer-Based Sheet And Film

Question 1

Explain the difference between the terms, transparency and translucency (2 marks)

Answer 1

• Transparent material allows light to pass through a material and enables a clear view through the material
• Translucent material only allows a little bit of light to travel through it, often with a degree of fuzziness and obscuring the view through to some extent

Question 2

Many polymers are flexible and can be used to form hinges.

Explain one disadvantage of using polymers to make hinges. (2 marks)

Answer 2

Polymers have a tendency to work harden as they are folded backward and forwards (1) which means the material can become brittle/stiff/hard and may break (1).

Question 3

Additives are blended into polymers for many reasons.
Name four different additives in the grid below and state one benefit for its inclusion. (8 marks)

Additive:
Benefits:

Answer 3

Additive: Fire Retardant
Benefits: To reduce the risk of fire / reduce flammability / reduce toxic fumes released when burnt
Additive: Plasticisers
Benefits: To enhance flow characteristics and enable polymers to be moulded at
higher temperatures
Additive: Thermal antioxidants
Benefits: To help to prevent oxidation due to heat exposure during the manufacturing process
Additive: Lubricants
Benefits: To improve polymer flow during moulding by decreasing viscosity
Additive: Antioxidants
Benefits: To reduce the degradation and deterioration from exposure to air and water and help prevent cracking and discoloration
Additive: UV light stabilisers
Benefits: To improve the material’s resistance to degradation by UV light
Additive: Plasticisers
Benefits: To make materials stretch/flow
Additive: Antistatic additives
Benefits: To reduce the build-up of static charge
Additive: Fillers
Benefits: To add bulk and improve the properties of polymers, reducing the amount of polymer used and thus weight and costs
Additive: Bio-batch materials
Benefits: To encourage biodegradability at end of use

Question 4

Give one source of natural polymers. (1 mark)

Answer 4

• Trees
• Animals
• Humans

Question 5

This question is about thermoplastics.

(a) What is polymerisation? (3 marks)
(b) Explain using notes and sketches how the polymer chains in thermoplastics are connected and how this affects the way they behave. (3 marks)

Answer 5

a) It is the chemical process of joining monomers together (1) end to end (1) to create long-chain polymers (1).

b) In thermoplastics, polymer chains are loosely entangled with allowing chains to slide over each other when heated (1). This means thermoplastics can be formed
using heat and reshaped many times without changing their properties (1). [For the last mark, google a diagram of polymer chains in thermoplastics to check if you have got it correct]

Question 6

Name one polymer that is commonly used in the manufacture of ropes for use in the marine industry and explain what properties make them suitable for this application. (2 marks)

Answer 6

Award 1 mark for naming the polymer and a further 1 mark for a relevant explanation.

Nylon – Nylon has a low coefficient of friction, it is durable and resistant to abrasion,
lightweight and it floats on water.
PP Polypropylene – flexible polymer with excellent fatigue resistance, is resistant to
chemicals and solvents, lightweight and floats on water.

Question 7

This question is about thermosetting plastics.
(a) Name the type of polymerisation used to create thermosets (1 mark)

(b) Explain how cross-linking occurs (1 mark)
(c) What type of reaction is caused? (1 mark)

Answer 7

a) Condensation polymerisation
b) A chemical catalyst is used to cure the polymer causing cross-linking to occur
c) An exothermic reaction

Question 8

With reference to both the physical and mechanical properties, evaluate the use of 
urea formaldehyde (UF) is used for plug sockets (2 marks)

Answer 8

Award 1 mark for each relevant property up to a maximum of 2 marks.

• Urea formaldehyde UF is a hard, opaque resin that can be cast to produce the form of the plug socket
• UF has good resistance to deformation by heat
• UF is an excellent thermal insulator
• UF I an excellent electrical insulator
• UF can be coloured using pigments to increase the visual appeal

Question 9

Explain one way in which UF is used as an adhesive in the timber industry (2 marks)

Answer 9

Award 1 mark for the usage and a further 1 mark for a relevant explanation

UF is used as an adhesive to bond materials such as:
- MDF where particles of waste material from the timber industry are formed into
a board using heat and pressure
- Plywood where layers of thin timber veneer are laminated to form a board

Question 10

Suggest and justify an appropriate polymer for use in the manufacture of the contact 
lens case (3 marks)

Answer 10

Award 1 mark for an appropriate polymer and up to 2 marks for a relevant justification.

Polymer – HDPE has a good strength to weight ratio and so will be light and portable whilst strong enough to protect fragile contents (1).

• It is tough and hard and so can resist impact and will not scratch or dent easily (1).
• It has good chemical resistance and so will not be harmed by contact lens solution (1).
• It is waterproof and impermeable protecting the contents from water, oxygen, and dust (1).

Question 11

A company designing play areas for primary schools is looking for an alternative surface to the sand currently in place. They have considered tarmac but decided this was too unforgiving a surface when children fall. They have looked at woodchips, however, it was found that this was too messy, and the woodchips could be walked into the school buildings on children’s shoes.

Suggest an alternative surface for the playground, explaining what advantages it has to offer (4 marks)

Answer 11

• Rubber granules or shreds could be used to create a safe playground surface.
• Rubber is more forgiving than tarmac if a child were to fall, it also absorbs impact so is better for running and jumping on.
• The rubber granules come in a variety of colours, so patterns or lettering can be created to make the playground more appealing.
• Granules are mixed with an adhesive on-site and then poured and left to cure, this is a relatively easy operation.
• It is easy to level uneven ground when pouring and spreading.
• The surface is safe all year round.
• The surface is easy to mend by cutting around the scuffed area and pouring in new granules.
• Recycled rubber can be used for this purpose.
  It is a long-lasting surface.

Question 12

Discuss the advantages and disadvantages of using fluted polypropylene sheet to make wine storage box

Answer 12

Advantages:
- It is lightweight meaning it does not add too much additional weight to the
product
- It is waterproof meaning it will not absorb any split liquids and can be
easily washed or wiped clean
- The fluting adds rigidity to the material without adding weight, so the box
is less likely to buckle
- The material is able to be cut and scored to allow the box to be created
and stored as a flat packed net and then folded constructed as needed
- The material is flexible when folded and can withstand repeated folding
without work hardening to the point of breaking
- The material is impact resistant protecting the glasses if handled
carelessly
Disadvantages:
- Hardwearing, robust plastic creates a sealed crate, if glasses are put away
wet the water won’t evaporate easily
- If folded carelessly new inaccurate folds can be created weakening the
material
- The plastic sheet may become slippery and difficult to hold if wet
- It not folded and interlocked correctly the load may fall out of the bottom
- If too many boxes are stacked one on top of the other, the bottom-most
box may buckle under the strain

Question 13

Discuss the advantages and disadvantages of using fluted polypropylene sheet to make a wine storage box

Answer 13

Advantages:
- It is lightweight meaning it does not add too much additional weight to the
product
- It is waterproof meaning it will not absorb any split liquids and can be
easily washed or wiped clean
- The fluting adds rigidity to the material without adding weight, so the box
is less likely to buckle
- The material is able to be cut and scored to allow the box to be created
and stored as a flat packed net and then folded constructed as needed
- The material is flexible when folded and can withstand repeated folding
without work hardening to the point of breaking
- The material is impact resistant protecting the glasses if handled
carelessly
Disadvantages:
- Hardwearing, robust plastic creates a sealed crate, if glasses are put away
wet the water won’t evaporate easily
- If folded carelessly new inaccurate folds can be created weakening the
material
- The plastic sheet may become slippery and difficult to hold if wet
- It not folded and interlocked correctly the load may fall out of the bottom
- If too many boxes are stacked one on top of the other, the bottom-most
box may buckle under the strain

Question 14

Explain two reasons why foam board is an appropriate material to make concept models of some modular storage furniture (4 marks)

Answer 14

Award 1 mark for a reason and 1 mark for an explanation to a maximum of 4 marks.

• It is available in a large flat sheet (1) which means that although the models are likely to be smaller scale, large single pieces can be used to represent the panels rather than having to join sheets, edge on edge (1).
• It is relatively inexpensive (1) and so adaptations and changes can be made where necessary without great cost (1).
• It is easy to cut using a scalpel, straight edge, and cutting mat (1) It has a good uniform thickness which means you can get a consistent, clean-cut (1).
• It is easy to join using adhesive, tape, or by creating slots (1) enabling the model maker to create 3D forms (1).
• It has an excellent flat surface finish (1) which could be laminated, painted, or printed to represent different materials (1).

Question 15

Explain one reason why solvent-based adhesives are not the best choice for joining foam board. (2 marks

Answer 15

The solvents are likely to dissolve the foam inner (1) which will result in the board collapsing/losing its core strength and rigidity / making parts hard to join (1)

Question 16

Explain one reason why it is important for polypropylene film to be able to withstand heat when being used in the food packaging industry (2 marks)

Answer 16

• It is quite often sealed to a container with food inside using a heat-sealing process (1) therefore it must be capable of withstanding the temperatures involved in this process (1).
• Sometimes food is sold hot or may need to be heated in a microwave (1) and the protective film covering the food must be able to withstand this heat and not contaminate the food (1).

Question 17

Describe using notes and sketches, the process of using a hot wire cutter to cut
Styrofoam, making sure you include any relevant health and safety issues (4 marks)

Answer 17

• A wire is hot via an electrical current passing through it (1).
• Fence guide is used to ensure a parallel cut (1).
• Material should be pushed through at a steady constant rate so as to give time for it to be cut without putting too much tension on the hot wire (1).
• Gloves should be worn in case you slip and burn/touch the hot wire (1).
• The room should be well ventilated and/or an appropriate mask is worn to prevent inhalation of fumes (1).

Question 18

With reference to both the physical and mechanical properties, evaluate the use of Plastazote foam as a swimming buoyancy aid for young children when learning 
to swim (6 marks)

Answer 18

Indicative content: Award credit for any other valid response.

• The foam is buoyant, being a foam with nitrogen-based bubbles, it will float in water
• It is a flexible material which means it can be bent around when formed in a long ‘tube-like’ sections to wrap around and support the body of a young child
• It is non-toxic therefore it will not affect the water or the skin of a child or be dangerous if chewed
• It has excellent chemical resistance therefore it will not be affected by the chlorine or chemicals in the swimming pool water
• It can be wiped clean or disinfected to make sure it is safe to use by a number of children
• It is weather and UV resistant and durable so it will not fade in sunlight if used or left outside

Question 19

A company specialising in running shoes for desert marathon runners is looking to improve the longevity of the soles on their shoes.

Suggest a specific material that could be used to create a new sole and explain the advantages this would offer the runner.

Answer 19

Polybutadiene, butadiene rubber, or BR.

• It is a strong synthetic rubber that is highly resistant to wear against friction which is important as runners are moving over sand and scree for prolonged periods.
• It also has excellent thermal resistance against friction which is ideal as the sand can reach very high temperatures.
• Like natural rubber, it has excellent tensile strength and is tough and elastic so should be able to withstand the rigours of a marathon and the wear and tear the shoes will be subjected to.
• It absorbs impact making it ideal for a running shoe that will encounter a variety of surfaces.

Question 20

Study the racing bike saddle pictured below and suggest how two elastomers could be used together in the design of a saddle cover to increase comfort.

Answer 20

• Neoprene (open cell) would make a suitable saddle cover. It is spongy and therefore comfortable, it is breathable, it can be cut and stitched to form the cover, and is stretchy so can be pulled over the saddle enabling it to fit snugly.
• Silicone (gel) sections could be integrated into the cover to increase cushioning and absorb the impact of the rider sitting from a standing position or riding over rougher ground. It will not react with sweat and will be protected from abrasion by the neoprene cover.

Question 21

Which one of the following describes the process of curing and hardening rubber? (1 mark)

• Vulcanisation
• Polymerisation
• Over moulding
• Cross-linking

Answer 21

• Vulcanisation

Question 22

Are all elastomers thermosetting? Explain your answer (3 marks)

Answer 22

Award 1 mark for each valid point up to a maximum of 3 marks.

No, thermoplastic elastomers known as TPEs (1) are polymer blends (1) that can be heated and moulded without forming cross-links (1). Most TPEs are known by their trade names (1). They display similar properties to the cross-linked elastomers (1) like rubber however unlike rubber, they can be reprocessed once moulded (1). TPEs offer faster processing times than cross-linked elastomers (1).

Question 23

Suggest one process that could be used during manufacture to improve the comfort and friction of the grip of toothbrush (1 mark)

Answer 23

• The use of over mouldings (1).

- The addition of a moulded texture (1).

Question 24

Evaluate the use of silicone in mould making for confectionery (6 marks)

Answer 24

• Silicone can be moulded into intricate shapes enabling a vast range of different confectionary forms
• Once moulded silicone is very stable so will retain its shape and ensure the confectionery is of consistent shape
• It is very smooth and that will be reflected in the finish on the confectionery
• Silicone is resistant to extreme temperatures so can cope with hot chocolate being poured in or being put in the freezer for setting
• It is non-reactive so is food safe for use with edibles
• It is self-lubricating enabling the confectioner to turn out the set confectionery easily and without damaging it
• It is malleable and smooth so easy to eject the food items and is also easy clean after use

Question 25

``` Explain one possible safety issue with wearable rubber or latex products like surgical gloves (2 marks) ```

Answer 25

Some people are allergic to rubber and or latex (1) and exposure can cause skin complaints (1).

Question 26

Photo-degradable polymers can be used to create plastic six-pack rings for drinks cans like the one pictured. What are the benefits of these? (5 marks)

Answer 26

Six-pack rings are single-use plastics and invariably get thrown away after use. Unfortunately, this can result in them being picked up by birds or if the plastic waste is left on beaches, wildlife and sea life can get tangled up in it. This can lead to strangulation, deformations in growth, poisoning, and starvation. If these single-use six-pack rings are made from photo-degradable polymers they could degrade before causing problems or, if picked up by wildlife, they will weaken to such an extent that it brakes and degrades releasing the animal, bird, or fish.

Question 27

Polylactide (PLA) sheets and film are used extensively as biodegradable single-use food packaging however, PLA granules are also used in the manufacture of reusable plastic items.

Answer 27

- It is made from renewable resources. - PLA can break down and decompose in a relatively short time given specific conditions in commercial composting facilities. - Because it is a synthetic biopolymer its life span can be built-in. - It can be moulded and formed just like any other thermoplastic. - It is food safe. - It is available in a range of colours. - PLA can be recycled with specialist facilities.

Question 28

Most local councils now collect food waste from households which have collected and stored it in special food waste bags

Answer 28

- Easy to empty the bin/cleaner rather than having food in contact with the bin which would then need to be washed out every time the bin is emptied. - Allows the contents to be sealed as the bag can be tied up to stop smells coming out. - Keeps all the waste together rather than falling out when it is being emptied into the bin lorry. - Old disused degradable carrier bags may be used which will not biodegrade. - Bags should be biodegradable/compostable so that they break down with the compost rather than non-biodegradable bags which will last for years. - If compostable bags are left in the caddy for too long, they will disintegrate and may cause a mess when removed. - Composting bags still need energy and resources to be made. - Old newspapers can be used to line the bins which are even more eco-friendly but not as convenient.

Question 29

Biodegradable polymers fall into two categories, define each category (2 marks)

Answer 29

- Those that are made from renewable raw materials including sugar and plant starches such as Polylactic acid (PLA) (1). - Those that are manufactured from petrochemicals with the addition of biodegradable additives (bio batch) which aid degradation (1).

Question 30

Define photo-degradation (1 mark)

Answer 30

Polymers that are photo-degradable will start to break down when exposed to UV light.

Question 31

Oxy-degradation is the degrading of polymers when exposed to oxygen (a) Suggest one advantage of this method of degradation (1 mark) (b) Suggest one disadvantage of this method of degradation (1 mark)

Answer 31

a) The time it takes to break down can be ‘built in’ to the material (1) Biodegradation doesn’t require any special condition other than access to oxygen (1) b) If bags are stored and reused, they may start to break down before they are disposed of or gone through their useful life/function.

Question 32

Evaluate the use of photo-degradable weed suppressant sheeting in allotments (6 marks)

Answer 32

- Photo-degradable polymers break down when exposed to UV light and so will naturally degrade over time without the need for further treatment - The sheeting will temporarily block out the light thus suppressing weed growth - In blocking out the light, the sheet will also keep the earth around the plants of seedlings warm, acting as a mulch and promoting faster crop development - The sheeting prevents the evaporation of water in the soil keeping roots moist - Sheeting is easy to lay, cut to size and cut holes through which to plant - Photo-degradable sheeting is a more environmentally friendly option than the use of chemical weed killers - Some people may find the sheeting aesthetically unattractive - The sheeting does take some time to break down and can look tatty as it does so - As it degrades it can break into smaller parts and be blown around and could prove a hazard to some wildlife

Question 33

Suggest and explain one reason why hospital laundry bags are sometimes made from hydro-degradable polymers (3 marks)

Answer 33

Award 1 mark for a valid reason and up to 2 marks for an explanation up to a total of 3 marks. Sheets, clothes, and other hospital-generated laundry may have been used by sick people with infectious conditions (1). If the orderlies remove the laundry wearing gloves and put it into a hydro-degradable bag, this can be sealed and then put straight into the wash without the need to remove and touch the laundry (1). The bag will then dissolve during the wash (1).

Question 34

``` Which one of the following is a synthetic biopolymer? (1 mark) • Biopol • Lactide • PotatoPak • PHA ```

Answer 34

- Lactide

Question 35

Give three reasons why corn starch polymer is suitable for single-use food packaging (3 marks)

Answer 35

Award 1 mark for each valid reason and up to a maximum of 3 marks. - It can be extruded to produce a sheet or film and can also be injection moulded - It is food safe and resistant to fats - It is oxy-biodegradable - It is UV resistant - It is printable

Question 36

Explain why Lactide is used in the manufacture of pills and casings (1 mark)

Answer 36

It is used in pill and capsule casings as it allows the slow release of the medication as it hydro-degrades.

Question 37

``` Glycolide is also a PLA based polymer. Suggest one appropriate use for Glycolide film (1 mark) ```

Answer 37

- Food packaging - Packaging wrap - Floristry wrap - Bin liners - Carrier bags - Horticultural sheeting - Medical and drug delivery materials (1).