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POLYMERS (Thermosets are hard and durable with good structural rigidity
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POLYMERS
Thermosets are hard and durable with good structural rigidity
They are:
able to withstand higher
temperatures
waterproof when solid, so ideal
for use in adhesives
a good electrical insulator
cannot be remoulded
Thermoforming
Also known as thermoplastics, when heated the plastic becomes soft and flexible
Thermoplastics can be remoulded without affecting the material’s physical properties
Don't have cross links
Thermoplastics can be repeatedly heated
and moulded
Thermoplastics are not suitable for use
in areas of heat or UV sensitivity
A good surface finish can be
achieved for superior aesthetics
They can be recycled
Each time the plastic is reheated
it will try to return to its original shape
– this is known as plastic memory
Thermosetting
Also known as thermosets, this plastic cannot be reformTed once set in to shape
Thermosets have strong chemical bonds between the molecules, which do not separate on heating
Thermosetting plastics have cross links.
Polyester resin is a viscous, pale polyester solution and the addition of a catalyst, hardens the resin
The hardened resin is tough with high abrasion resistance which makes a high-performance coating for areas of high wear, for example flooring
Clear polyester resin is suitable for object embedding, clear sculpture casting and jewellery making
Resin replicas e.g. anatomical models can also cast be cast and painted
Polyester resin is commonly used with composite materials such as fibreglass
Lightweight and
weatherproof, it’s
used to adhere
layers of fibreglass
in the making of
boat hulls, vehicle
parts and panels
for caravans
Polymers are mostly synthetic materials
They are usually derived from finite resources such as coal, natural gas or crude oil
More renewable and sustainable materials such as vegetable starches are being used to make bio-plastics
This is the most common thermoplastic with over
80 million tonnes produced globally each year
There are several types of polyethylene including
Polyethylene terephthalate (PETE)
High density polyethylene (HDPE)
Low density polyethylene (LDPE)
Polyethylene can be rigid with good strength to weight ratio
It has good ductility and impact strength
Its stability makes it a suitable plastic for blow-moulding
Thermoplastics must be recycled separately to enable reuse, where possible
In order to easily separate items, thermoplastics are
marked with a common code
Polyethylene terephthalate
High-density polyethylene
Polyvinyl chloride
Low-density polyethylene
Polypropylene
Polystyrene
Other plastics, such as acrylic, nylon and polycarbonate
Melamine is a hard thermoset
A heavy material, it has good resistance to heat, chemicals
and moisture
It has good resistance to scratches,
but it is prone to chipping
Available in a range of colours and thicknesses, it is often used for picnic wear and as a laminate for
kitchen surfaces
PVC is widely used for packaging, pipes, outerwear, electrical tapes and children’s toys
PVC can be rigid and commonly used for making pipes
It is tough and easily extruded
With the addition of plasticisers, it becomes flexible
Urea formaldehyde is a good electrical insulator
With good heat resistance it is used for
manufacturing electrical fittings
The textiles industry treats some fabrics with
UF resins to promote easy care properties
such as anti-wrinkling
The paper industry uses UF to improve
tear strength
The timber industry uses UF resin to
bind particles in the making of
manufactured boards such as MDF
Polyethylene terephthalate
Lightweight, chemically resistant, stable, easily blow moulded
High density polyethylene
Lightweight, rip and chemical resistant, stiff and resists cracking
Low density polyethylene
Flexible, tough, high strength to weight ratio, easily extruded into sheets
Epoxy resins are a class of
reactive polymers
Supplied as two liquids; a resin with a
hardener which acts as a catalyst to
set the resin
Epoxy resins are used as adhesives,
for example Araldite®
With a good strength to weight ratio, epoxy adheres well to fibreglass and carbon fibre, reinforcing it
Plastics can be formed using a variety of processes
Blow moulding – forming hollow plastic items
Extrusion – creating objects with a cross section profile
Injection moulding – injecting softened plastic into a mould
Vacuum forming - sheet of softened plastic forced onto a mould
A very versatile polymer, polypropylene is used for solid plastics, films and fibres
It has low density, making it lightweight
It is ductile, enabling it to stretch for use in fibres and films
It’s chemically resistant and easily cleaned which makes
it very suitable for food containers
HIPS is shatterproof and a good insulator
It’s flexible and lightweight so ideal for vacuum forming
Impact resistant, it is suitable for food containers particularly yoghurt pots and fast food containers
HIPS is easily mouldable and has a good gloss finish
Acrylic Polymethyl-
Methacrylate
This versatile and hard wearing plastic, comes in a variety of thicknesses and colours
It’s a tough plastic, but becomes
brittle if very thin
It can also be spun into
threads and woven