Plastics & Adhesives

Plastics can be derived from• Coal• Natural Gas• Other Petroleum Products• Cotton• Wood• Waste Organic Matter

• From the base product monomers are extracted.

• These monomers react with each other to form chains which are called polymers

• See diagram page 1

Development

• Plastics are being used in many facets of our industry

• Where do we see plastic?

Two Types of Plastic

1. Thermoplastics

2. Thermosetting Plastics

Types of Plastic

1. Thermoplastics

• Become Soft when heated• Reharden when cooled• This process can be repeated to allow the plastic

to be moulded or formed to a required shape• Constant Cooling & Reheating will affect it’s

appearance & Strength• Soften then catch fire

Types of Plastic

2. Thermosetting plastics (Thermosets)

• Undergo a irreversible chemical change during production

• Will not soften when heated• Will not soften before catching fire• Cannot be moulded or bent to shape

Properties of Plastics

• Strength –

• High Tensile Strength to weight ration• Due to elasticity they are not suitable for

structural applications• Heat will also degrade when heat applied• Thermal Expansion can be as much as 10 x

steel

Properties of Plastics

• Thermal Conductivity

• Expanded Plastic has Low Thermal Conductivity

• Foamed Plastics are good insulators

Properties of Plastics

• Electrical Properties

• Non Conductors• Will build up Electrostatic Charges• Attract Charges• Sparking Can Occur- This has OH&S

Implications

Properties of Plastics

• Combustibility

• Will catch fire when open flame applied• Will propagate fire• Additives can be used to retard fire- usually

will still burn when open flame applied and self extinguish when flame removed.

• Gases emitted are toxic• Some plastic will melt and cause injury

Properties of Plastics

• Durability

• Do not corrode• Will be degraded by UV radiation which will

break down the plastic• Plastic for External use must be UV stabilised

Properties of Plastics

• Environmental Hazards

• Not Biodegradable• May be recycled• Burning released toxic gases

Plastics in the Building Industry

• Polythene – Builders Plastic- Concrete Underlay – Thermoplastic

• Polyvinyl Chloride – PVC Pipes, Roof & Wall sheeting, Vinyl Floor Covering, Electric Cabling

• Resistant to Fire

Plastics in the Building Industry

• Polyvinyl Acetate (PVA), Glue, Curing Compound, Bonding agent for Plaster, Insitu Floor Coverings

• Polymethyl Methacrylate (Acrylic) – Roof Sheeting

• Polystyrene – Insulation, Form Voids in concrete – easily dissolved by organic solvents

Plastics in the Building Industry

• Teflons – Resistant to heat, very low friction, plumbers tape

• Nylons – Nuts, bolts, Carpets, Door Fittings

• Polycarbonates – High Ductility, High Tensile, Roof Sheeting, Bullet Proof Glass

Plastics in the Building Industry

• Bakelite –, Thermosetting Oldest form of plastic, Electrical fittings, resistant to ignition

• Resorcinal Formaldehyde – Waterproof & Boil proof Glue

• Polystyrene – Insulation, Form Voids in concrete – easily dissolved by organic solvents

Adhesives

• Originally based on animal and vegetable matter – Horse Glue!

• Last 20 years synthetic glues developed that provide high stress bonds

General Properties

Properties vary• Some are Highly Flammable eg Contact

Adhesives• Liquid Nails is Flammable and degrade

polystyrene while Liquid Nails Fast Grab is not flammable and will not degrade polystyrene

Types of Adhesives

Adhesives from Natural Products• Wall paper paste based on cellulose

Only suitable for Interior use

• Susceptible to attack by micro- organisms

Types of Adhesives

Adhesives from Natural Products• Bituminous Adhesives resistant to water and

many chemicals

• May reactivate under heat

• Used for Vinyl & Parquetry

• Bonding of Roof Felt