Properties of PVC (Polyvinyl Chloride) Plastic
Chemical Structure:
Composed of vinyl chloride monomers (CH₂=CHCl).
High chlorine content (56-57%), contributing to flame resistance and durability.
Physical Properties:
Form: Can be rigid (uPVC/unplasticized) or flexible (with plasticizers like phthalates).
Density: 1.3–1.45 g/cm³, heavier than many plastics due to chlorine.
Color: Naturally white/translucent; easily colored with pigments.
Mechanical Properties:
Strength: Rigid PVC has high tensile strength (50–80 MPa).
Impact Resistance: Brittle at low temperatures unless modified with impact additives.
Durability: Long-lasting with resistance to abrasion and wear.
Thermal Properties:
Melting Point: Decomposes at ~140–260°C, releasing toxic HCl gas.
Glass Transition Temperature (Tg): ~80°C.
Thermal Stability: Requires stabilizers to prevent degradation during processing.
Electrical Properties:
Excellent insulator, widely used in electrical cables and coatings.
Flame-retardant and self-extinguishing due to chlorine content.
Chemical Resistance:
Resistant to acids, bases, salts, oils, and aliphatic hydrocarbons.
Poor resistance to aromatic hydrocarbons, ketones, and chlorinated solvents.
Low permeability to gases and liquids.
Environmental and Safety Aspects:
Recycling: Challenging due to additives; mechanical recycling is common.
Toxicity: Burning releases dioxins and HCl. Vinyl chloride monomer is carcinogenic.
Durability: Long lifecycle reduces replacement frequency but complicates disposal.
Weather Resistance:
Susceptible to UV degradation unless stabilized with additives like TiO₂.
Becomes brittle over time when exposed to sunlight without stabilizers.
Applications:
Rigid PVC: Pipes, window frames, bottles.
Flexible PVC: Cables, flooring, medical tubing.
Other Uses: Signage, roofing membranes, synthetic leather.
Processing:
Easily welded using solvents or heat.
Compatible with extrusion, injection molding, and calendaring.
Summary:
PVC is versatile, cost-effective, and durable but poses environmental and health challenges during production and disposal. Its properties vary significantly with additives, making it adaptable for diverse applications.