Comprehensive Guide to Polyvinyl Chloride (PVC) Resin Properties

Polyvinyl chloride (PVC) resin is a thermoplastic polymer produced by free radical polymerization of vinyl chloride monomer (VCM) under the action of an initiator. Its chemical formula is —[CH₂—CHCl]ₙ—, and its CAS number is 9002-86-2.

PVC is the world's third largest synthetic plastic polymer in terms of production volume (after polyethylene and polypropylene), with a global annual production capacity of approximately 58 million tons, of which pure resin (primary form) accounts for about 40 million tons annually (IndexBox, 2024). Industrially produced PVC typically has a molecular weight ranging from 50,000 to 120,000, exhibits an amorphous structure, and has a low degree of branching.

Solubility and Chemical Resistance: PVC has poor solubility, being insoluble in water, ethanol, gasoline, and vinyl chloride monomer; it is only soluble in a few specific polar organic solvents such as cyclohexanone, tetrahydrofuran (THF), dichloroethane, and dimethylformamide (DMF). It is also soluble in mixed solvent systems such as acetone-carbon disulfide or acetone-benzene (used in the spinning of chlorofiber fibers).

PVC is insoluble in hydrochloric acid, ethers, or alcohols—on the contrary, it exhibits excellent corrosion resistance to acids, alkalis, and salts such as hydrochloric acid (any concentration), sulfuric acid (below 90%), nitric acid (below 50–60%), and sodium hydroxide (below 20%) at room temperature. Its chemical stability decreases with increasing operating temperature.

Flame retardancy: The PVC molecular chain contains approximately 56.8% chlorine (Cl atomic weight 35.5 / chain segment molecular weight 62.5), giving it natural flame-retardant and self-extinguishing properties. Its limiting oxygen index (LOI) can reach over 40, and it self-extinguishes upon removal from a flame, requiring no additional flame retardants.

Electrical insulation: PVC has excellent dielectric properties, high volume resistivity, and a dielectric constant of approximately 3.0–4.0, making it an excellent low-voltage electrical insulation material widely used in the insulation layer and sheathing of wires and cables.

Mechanical Properties: Rigid PVC has a tensile strength of approximately 60 MPa and an impact strength of 5–10 kJ/m². It is hard but brittle. The toughness can be significantly improved by adding impact modifiers (such as CPE and acrylate-based ACRs).

Polymerization Process and Raw Material Route

There are three main polymerization processes for industrial PVC production:

Suspension Polymerization (SPVC): This is the most important process, accounting for approximately 80% of global PVC production. VCM is suspended and dispersed in an aqueous medium in droplet form (particle size 50–250 μm).

Polymerization is initiated by an oil-soluble initiator (organic peroxide or azo compound) at a polymerization temperature of 45–65℃. The degree of polymerization (600–1600) is mainly determined by the reaction temperature, and the amount of initiator adjusts the polymerization rate. Dispersants (such as polyvinyl alcohol and hydroxypropyl methylcellulose) control the resin particle morphology.

Emulsion polymerization (EPVC/paste resin): Yield approximately 10%, fine particle size, large specific surface area, suitable for paste resin applications such as artificial leather coatings, dipped gloves, and toys.

Bulk polymerization: Solvent-free and anhydrous, high product purity, but lower yield.

There are two main raw material routes for the preparation of VCM monomers:

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