Chapter 17 - Polymers

What is the definition of a 'physical property' in the context of materials?

The characteristics of a material, such as its appearance and features.

What is another term for a material's 'working property'?

Mechanical properties.

How is a 'working property' of a material defined?

The way in which a material responds to an external force or certain environment.

What does it mean for a material to be 'naturally occurring'?

It comes from nature and is not made or altered by humans.

What does it mean for a material to be 'manufactured'?

It is produced by humans, often using machinery.

Define the term 'synthetic' in relation to materials.

A material made through chemical processes.

What are the three main categories into which polymers can be placed?

Thermoplastics (or thermo polymers), thermosetting plastics (or thermosets), and elastomers.

What are the two main categories for polymers based on their origin?

Naturally occurring and synthetic.

What is the primary source of most synthetic polymers?

Fossil fuels such as crude oil, gas, and coal.

How can polymers often be identified for recycling purposes?

Through the number inside their recycling triangle.

The number 2 inside a recycling triangle stands for which polymer?

High-density polythene (HDPE).

What is the defining characteristic of thermo polymers (thermoplastics)?

They melt on heating and can be repeatedly reshaped and remoulded.

Are thermoplastics generally recyclable?

Yes, because they can be repeatedly reheated and remoulded.

What is the defining characteristic of thermosetting polymers?

They do not melt on heating, can only be formed once, and will burn at extreme temperatures.

What happens at a molecular level when thermosetting polymers are formed that prevents them from being reshaped?

A chemical reaction causes cross-linking between the long chain molecules which cannot be broken by heat.

Are thermosetting polymers easily recycled?

No, they are often difficult to recycle because they cannot be remelted and reshaped.

What is the defining characteristic of elastomers?

They are soft, flexible polymers with good elasticity, meaning they can be distorted but will return to their original shape.

What is the origin of High-Density Polythene (HDPE)?

It is a synthetic polymer made from fossil fuels.

List three working properties of High-Density Polythene (HDPE).

Lightweight, resistant to chemicals, and high impact resistance.

Name two common products made from High-Density Polythene (HDPE).

Milk bottles and recycling/refuse wheelie bins.

What is the origin of Polylactic Acid (PLA)?

It is a manufactured polymer often made from cornstarch or sugars.

What are two key properties of Polylactic Acid (PLA)?

It is biodegradable and has a low melting point.

What is a primary application for Polylactic Acid (PLA)?

3D printer filament.

What is the origin of shellac?

It is a naturally occurring polymer secreted by the lac bug.

Name a product that is an example of shellac use.

Nail varnish or timber varnishes.

What is the origin of urea-formaldehyde?

It is a synthetic polymer made from fossil fuels.

List two key properties of urea-formaldehyde.

It has high heat resistance and is a good electrical insulator.

What are urea-formaldehyde polymers commonly used for?

Electrical fittings such as plug sockets and light switches.

What is the origin of silicone?

It is a synthetic polymer made from fossil fuels.

List two key properties of silicone.

It has excellent heat resistance and is non-stick.

Name two common applications of silicone.

Flexible baking trays and bathroom sealant.

_____________ polymers can be heated and formed repeatedly and are therefore often recyclable.

Thermoforming

What are the physical properties of Acrylic (PMMA)?

It is hard, brittle, shiny, and available in a wide range of colours.

What are three common uses for Acrylic (PMMA)?

Car lights, visors, and baths.

What are the physical properties of High Impact Polystyrene (HIPS)?

It is rigid, cheap, and available in many colours.

What is a major safety concern when burning High Impact Polystyrene (HIPS)?

It is toxic when burned.

Name two products made from High Impact Polystyrene (HIPS).

CD cases and yoghurt pots.

What are the physical properties of High Density Polythene (HDPE)?

It is stiff, strong, and lightweight.

What are some common uses of High Density Polythene (HDPE)?

Washing baskets, pipes, and chairs.

What are the working properties of Polypropylene (PP)?

It is tough and flexible.

A key working property of Polypropylene (PP) is its good fatigue resistance, making it suitable for what type of feature?

A hinge property (e.g., on hinged container lids).

Name two items commonly made from Polypropylene (PP).

Plastic chairs and medical equipment.

What are the working properties of Polyvinyl Chloride (PVC)?

It is brittle but durable and can be extruded or in flat sheets.

Name two common applications for Polyvinyl Chloride (PVC).

Blister packs and window frames (uPVC).

What are the key working properties of Polyethylene Terephthalate (PET)?

It is light, strong, and tough.

What is a very common application for Polyethylene Terephthalate (PET)?

Drinks bottles.

_______________ polymers can only be formed once, are hard to recycle, and are good insulators.

Thermosetting

How is Epoxy Resin (ER) typically supplied?

As two parts: one resin and one hardener, which combine to create a strong adhesive.

What are two working properties of Epoxy Resin (ER)?

It is rigid, durable, strong, and heat resistant.

What is Melamine Formaldehyde (MF) commonly used for?

Picnic wear, worktops, and decorative laminates.

What property of Melamine Formaldehyde (MF) makes it suitable for kitchenware?

It is food safe.

What are the physical properties of Phenol Formaldehyde (PF)?

It is rigid and brittle.

Name a product made from Phenol Formaldehyde (PF).

Snooker balls or bottle caps.

What are the key working properties of Polyester Resin (PR)?

It is strong, heat resistant, and a good insulator.

What is a common use of Polyester Resin (PR), especially when reinforced with fibres?

Waterproofing, boat hulls, and car body parts.

What are the key working properties of Urea Formaldehyde (UF)?

It is heat resistant, hard, brittle, and easily injection moulded.

List three unique properties that make polymers useful for modern applications.

Good electrical/thermal insulators, good strength-to-weight ratio, and good chemical resistance.

What kind of finish can polymers have without additional processes?

They can be self-coloured, opaque or transparent, and are self-finishing.

What is the common application for Low Density Polyethylene (LDPE)?

Squeezy detergent bottles, carrier bags, and food wrap film.

What are the properties of Polymethyl-methacrylate (PMMA) / Acrylic?

Tough, hard, and available transparent or translucent.

What are two common uses for Polyamide (Nylon)?

Bearings, gears, combs, and brushes.

Which polymer is described as extremely tough, hard, with good heat resistance and used for telephone handsets?

Acrylonitrile butadiene styrene (ABS).

What is rigid polyvinyl chloride (uPVC) commonly used for, due to its good weathering resistance?

Window frames, guttering, and pipes.

What are common uses for flexible polyvinyl chloride (PVC)?

Hose pipes, cable insulation, and fake leather.

What type of polymer is Liquid Silicon Rubber (LSR)?

It is a thermosetting elastomer.

What is a major advantage of Liquid Silicon Rubber (LSR) concerning temperature?

It can withstand temperatures ranging from -50°C to +250°C.

Name an elastomer known for its high tensile strength and use in car tyres.

Natural rubber (polyisoprene).

Which elastomer is tough with excellent wear resistance, making it suitable for shoe soles and water hoses?

Butadiene rubber (BR).

What are the properties of Neoprene (polychloroprene rubber)?

Good thermal resistance, tough, good oil resistance, and excellent weather resistance.

What is Neoprene commonly used for?

Wetsuits, laptop cases, and door seals.

Which elastomer has good flexibility at low temperatures and is used for flexible bakeware and medical uses?

Silicone.

What is a Thermoplastic Elastomer (TPE)?

A polymer with rubber-like properties that can be processed using conventional moulding equipment and is generally recyclable.

What is a significant advantage of using Thermoplastic Elastomers (TPEs) in manufacturing?

They have quicker production times compared to natural rubbers, and waste material can be recycled.

What are Thermoplastic Elastomers (TPEs) commonly used for?

Wire coatings, automotive seals, and over-moulding of grips onto tools and utensils.