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Polyvinyl chloride (PVC), with CAS No. 9002-86-2 and a molecular weight typically ranging from 24,000 to 100,000 g/mol, is a thermoplastic resin.
- Appearance and Physical Properties
Appearance:
Powder form: white powder (the most common industrial form).
Granular form: white or pale yellow granules (the processed form).
Odor: odorless and tasteless.
Hand feel: The powder has a fine, smooth texture; the finished product’s hand feel varies with the plasticizer content, ranging from rigid (e.g., water pipes) to flexible (e.g., synthetic leather).
-Physical parameters
Density: 1.35–1.45 g/cm³ (25°C), depending on the additive content.
Glass transition temperature (Tg): 77°C–90°C (this is the temperature at which PVC becomes rigid).
Melting point: No definite melting point. Softening begins at around 80°C, transitioning to a viscoelastic state at 130°C, and entering the viscous flow state between 160°C and 180°C (the decomposition temperature is approximately 200°C; therefore, stabilizers must be added during processing).
Refractive index: 1.544.
Solubility: Insoluble in water, ethanol, and gasoline; soluble in acetone, cyclohexanone, dichloroethane, tetrahydrofuran, and other organic solvents.
- Chemical properties
Stability:
Chemical corrosion resistance: Excellent. Exhibits outstanding resistance to acidic, alkaline, and saline media, such as hydrochloric acid, sulfuric acid, and sodium hydroxide.
Weather resistance: It exhibits good resistance to atmospheric aging; however, under the combined action of ultraviolet radiation and heat, it undergoes photooxidation and thermal degradation, resulting in discoloration (yellowing or browning) and embrittlement.
Thermal stability: poor. This is the greatest weakness of PVC. At temperatures above 100°C or under prolonged exposure to sunlight, PVC decomposes, releasing **hydrogen chloride (HCl)** gas, which in turn accelerates further decomposition through autocatalysis, leading to rapid material degradation. Therefore, stabilizers—such as calcium–zinc compounds and organotin compounds—must be added during PVC processing.
Flame retardancy: Excellent. The oxygen index is as high as 45% or more, and the material self-extinguishes upon removal from the flame, making it a self-extinguishing material.
Electrical insulation: excellent; it is an outstanding insulating material.
Uses
PVC is one of the most widely used plastics; depending on the plasticizer content, it is classified as rigid PVC (UPVC) or flexible PVC.
A. Rigid PVC (with no plasticizers or only a very small amount)
Characteristics: hard, high mechanical strength, and excellent chemical resistance.
Building materials: PVC water pipes (supply and drainage), custom-shaped profiles for doors and windows, skirting boards, and vinyl flooring.
Industrial applications: chemical pipelines, valves, pump bodies, and corrosion-resistant vessels.
Electronics and electrical: wire and cable insulation, socket housings.
Daily necessities: credit cards, hard-shell suitcases, and labels for mineral water bottles (shrink film).
B. Soft PVC (containing a large amount of plasticizer)
Features: soft, elastic, and low-temperature resistant.
Artificial leather: sofa leather, automotive interior leather, and leather bags.
Films and Sheets: Agricultural films, food preservation films, and tablecloths.
Electrical wires and cables: cable sheaths (especially those requiring cold resistance).
Sealing materials: sealing strips, gaskets, and hoses.
Toys and stationery: inflatable toys, erasers, soft rubber covers.