properties of polymers

thermoplastics

PPP PHN ALPH

• Thermoplastics can be reheated and reshaped, this gives them a wide range of appications

• Both types of polymer can be recycled but thermoplastics are easier to recycle

• Both types of polymers can be easily pigmented (coloured)

• Thermoplastics are prone to UV degradation

• Both polymers are heat and eletrical insulators

• Both polymers are hygenic, easily cleaned and waterproof

Production and extraction

• Fractional distillation of crude oil produces hydrocarbons

• One of the factions produced is called naphtha, and is the main once used for the production of polymers

Hydrocarbon chains:

• Cracking breaks large hydrocarbons into smaller and more useful forms

• Small → low bp, very volatile, flows easily and ignites easily

• Large → high bp, not volatile, doesn’t flow or ignite easily

Stock forms for polymers

• Sheet – Large, flat sections of polymer used for signage, packaging, and protective covers.

• Film – Thin and flexible polymer material used for packaging, wrapping, and waterproofing.

• Granules – Small pellets of polymer, commonly used in injection moulding and extrusion processes.

• Rod – Solid cylindrical shape used for machining, structural applications, and components.

• Other extruded forms – Includes tubes, channels, and profiles used in construction, insulation, and automotive applications.

• Foam – Lightweight polymer with air pockets, used in cushioning, insulation, and protective packaging.

• Powder – Fine polymer particles used in coatings, sintering processes, and rotational moulding.

Polypropylene (PP)

Thermoplastic - melting point 130c, safe working temp 100c, used for medical syringes, carpets, kitchenware

Advantages

• Lightweight

• Hard

• Impact resistant

• Chemical resistant

Disadvantages

• Can discolour from UV light

• Oxidation can cause problems

• Not heat resistant

• Difficult to paint

Polymethyl Methacorylate (Acrylic) (PMMA)

Thermoplastic - melting point 160c, safe working temp 95c, used for CD cases, baths, glass replacement

Advantages

• Stiff

• Hard

• Durable

• Good electrical insulator

• Available in a range of colours

Disadvantages

• Very brittle

• Scratches easily

• Splinters easily

• Poor fatigue properties

Rigid Polyvinyl Chloride (uPVC)

Thermoplastic - melting point 100c, safe working temp 95c, used for windows, guttering and pipes

Advantages

• Good chemical and weather resistance

• Durable and long-lasting

• Rigid

• Good electrical insulator

Disadvantages

• Can degrade under UV light

• Releases toxic fumes when burned

• Difficult to recycle

Flexible Polyvinyl Chloride (PVC)

Thermoplastic - melting point 100c, safe working temp 95c, used for hosepipes and cable insulation

Advantages

• Good chemical and weather resistance

• Durable and long-lasting

• Flexible

• Good electrical insulator

• Can be foamed which adds volume without weight

Disadvantages

• Can degrade under UV light

• Releases toxic fumes when burned

• Contains plasticisers that may leach out

• Difficult to recycle

High Impact Polystyrene (HIPS)

Thermoplastic - melting point 217c, safe working temp 70c, used for food packaging, preproduction prototypes and childrens toys

Advantages

• More durable than regular PS

• Rigid with low shrinkage

• Easy to mould and press

• Good dimensional stability

• Accepts paints and glues well

• Low cost material

Disadvantages

• Poor chemical resistance

• Brittle at low temperatures

• Poor UV resistance (yellows outdoors)

• Flammable (releases toxic fumes when burning)

Nylon (Polyamide)

Thermoplastic - melting point 258c, safe working temp 150c, used for bearings, gears, ropes and cable ties

Advantages

• High strength and durability

• Good wear resistance

• Low friction coefficient

• Resistant to chemicals and abrasion

Disadvantages

• Absorbs moisture, reducing strength

• Can degrade under UV light

• Produces static electricity

• Difficult to recycle

Polyethylene Terephthalate (PET)

Thermoplastic - melting point 260c, used for fibres in clothing, food containers and washing up bottles

Advantages

• Good alcohol and oil barrier

• Weather resistant

• Can be made transparent

• Inert/non-toxic

• Stiff/tough/hard

• Available in a range of colours

Disadvantages

• Can discolour from UV light

• Needs to be treated when used for food containers

• Susceptible to heat degradation

Acrylonitile Butadiene Styrene (ABS)

Thermoplastic - melting point 220c, safe working temp 80c, used for lego, helmets, suitcases, fidget spinners

Advantages

• Good chemical resistance

• Hard

• Tough/durable

• Heat resistant

• Naturally good finish

• Great for injection moulding

Disadvantages

• Can discolour from UV light

• Poor solvent resistance

Low Density Polyethylene (LDPE)

Thermoplastic - melting point 105c , safe working temp 65c, used for squeezy bottles, plastic films, plastic bags

Advantages

• Highly flexible and soft

• Good chemical resistance

• Easy to process and seal

• Transparent in thin films

Disadvantages

• Lower strength than HDPE

• Poor heat resistance

• Prone to UV degradation

• Can deform under load

High Density Polyethylene (HDPE)

Thermoplastic - melting point 120c , safe working temp 65c, used for milk jugs, detergent bottles, pipes, toys, cutting boards

Advantages

• High strength-to-density ratio

• Resistant to impacts and chemicals

• Stiff and durable

• Good moisture barrier

• Waxy texture

Disadvantages

• Less flexible than LDPE

• Susceptible to stress cracking

• Difficult to bond (needs welding/adhesives)

• Limited transparency

thermosetting polymers

PEMU

• Burn with too much heat

• Both types of polymer can be recycled

• Thermosetting polymers are heat resistant and more durable, they retain their shape when heated

• Both types of polymers can be easily pigmented (coloured)

• Both polymers are heat and eletrical insulators

• Both polymers are hygenic, easily cleaned and waterproof

Polyester Resin

Thermosetting polymer -, safe working temp 95c, used for chair sets, GRP, CFRP and garden furniture

Advantages

• Good electrical insulator

• Heat resistant

• Hard

• Cost effective

Disadvantages

• Short shelf life

• Emissions are harmful

• Brittle unless treated

Epoxy Resin

Thermosetting polymer - safe working temp 150c, used for adhesives, paints and electronics

Advantages

• Corrosion resistant

• Electrical insulator

• Good bond qualities

• Rigid

Disadvantages

• Causes health issues/toxic fumes

• Brittle

Melamine Formaldehyde (MF)

Thermosetting polymer - safe working temp 130c, used for buttons, electrical insulation and laminates

Advantages

• Hard and durable

• Excellent heat resistance

• Good chemical and moisture resistance

• Scratch and stain resistant

Disadvantages

• Brittle and can shatter under impact

• Not recyclable

• Can release formaldehyde during production

• Limited flexibility

Urea Formaldehyde (UF)

Thermosetting polymer - safe working temp 80c, used for wood glue for plywood or chip board as well as toilet seats and plug sockets

Advantages

• Strong

• Hard

• Heat resistant

• Good electrical insulator

Disadvantages

• Can emit toxic vapours during manufacture

• Brittle