Plastic Classification: Thermoplastics, Thermosets, and Elastomers
Classification of Plastics: Thermoplastics, Thermosets, and Elastomers
Thermoplastics
Thermoplastics are derived from petroleum. The polymer chains are linked together weakly. They soften when heated and can be molded, retaining their shape upon cooling. This process can be repeated.
Types of Thermoplastics:
- PVC (Polyvinyl Chloride): Tough and waterproof, used in pipes, shoe soles, and gloves.
- Polystyrene: Transparent or pigmented, used in films for packing and wrappers. Expanded polystyrene is used in packaging and for sound and heat insulation.
- Polyethylene:
- High density: Rigid and strong, used in transparent cube containers and bottles.
- Low density: Soft and light, used in bags and glasses.
- Perspex (Plexiglass): Transparent, used in lighthouses, windows, and protective glasses.
- Teflon (Fluorocarbon): Non-stick, used in utensils and countertops.
- Cellophane: Transparent, flexible, strong, shiny, and adherent, used in packaging.
- Nylon (PA or Polyamide): Translucent, shiny, flexible, resistant, and waterproof fabric used in toothbrushes.
Thermosetting Plastics
Thermosetting plastics are derived from petroleum. They are formed from strongly linked chains in various directions. They stiffen when heated only once and cannot be reshaped. They are hard and extremely tough, but more fragile than thermoplastics.
Types of Thermosetting Plastics:
- Polyurethane (PUR): Spongy, flexible, soft, elastic, and adherent, used in foam mattresses, seats, sponges, rods, glues, and varnishes.
- Phenolic Resin (PH): Bakelite, reinforced with glass fibers for shock resistance, asbestos for heat resistance, dark colored, electrically insulating, used in cookware handles, gears, housings, and switches.
- Melamine: Light, strong, hard, odorless, tasteless, thermal insulation, used in electrical, thermal, and acoustic insulation, tableware, and containers.
Elastomers
Elastomers are obtained through vulcanization (mixing rubber with sulfur at 160°C), which gives them elastic properties. They are formed by chains attached laterally and folded back on themselves. When force is applied, the chains stretch, giving them great elasticity and hardness.
Types of Elastomers:
- Natural Rubber: Obtained from latex, resistant and inert, used in thermal and electrical insulation, mattresses, and tires.
- Synthetic Rubber: Derived from petroleum products, resistant to chemical agents, used in tires, steering wheels, shock absorbers, tubing, sponges, and gloves.
- Neoprene: A synthetic rubber, harder, more durable, and waterproof, used in immersion suits, joints, hoses, and gloves.
Properties of Plastics
Plastics are materials made of polymers formed by long chains of carbon atoms.
Origins:
- Natural Plastics: Obtained directly from raw materials like cellulose (cellophane) or casein.
- Synthetic Plastics: Made from petroleum products, natural gas, or charcoal. Most plastics are in this group. The industrial transformation of these materials is called polymerization.
Properties:
- Physical Properties: Hardness, elasticity, rigidity, toughness, and flexibility vary depending on the type of plastic.
- Common Properties:
- Mechanical: Malleability, ductility, mechanical strength.
- Acoustic: Sound insulation.
- Thermal: Thermal insulation.
- Electrical: Electrical insulation.
- Other: Lightweight and waterproof.
- Ecological Properties: Most plastics are not biodegradable and are eliminated by incineration. They can also be recycled.
- Recycling:
- Chemical Recycling: Recovering the original constituents to gain new materials.
- Mechanical Recycling: Crushing the plastic into granules to produce new plastic or agglomerates.