PVC: Characteristics
What K-value tells a pipe maker
What this tab covers The physical and chemical properties that set its grade, price and uses, with the commercial grades and the standards that define them.Suspension PVC is sold by K-value (a measure of molecular weight), porosity, bulk density and residual VCM. Rigid uses want higher bulk density and thermal stability; flexible uses want porous resin that absorbs plasticiser. PVC is useless without additives: stabilisers, lubricants, impact modifiers and plasticisers make up a large part of the compound.
Properties that matter commercially
| Property | Value / specification | Why it matters | Source |
|---|---|---|---|
| K-value | about 57-58 for fittings and bottles; 65-67 for pipe and profiles; 70+ for flexible film and cable (indicative) | Higher K-value gives strength but needs more heat to process. | industry standard (indicative) |
| Chlorine content | about 56.7% by mass (CPVC about 63-67%) | Gives inherent flame retardancy and reduces oil use per tonne. | stoichiometric |
| Residual VCM | typically under 1 ppm in resin (indicative) | Food and medical rules limit carcinogenic monomer. | industry standard (indicative) |
| Bulk density and porosity | about 0.45-0.60 g/cm3 (indicative) | Sets extruder output and plasticiser uptake. | industry standard (indicative) |
| Carbon content | about 38% by mass | About 1.4 t CO2 per t if incinerated, plus HCl that must be scrubbed. | stoichiometric |
Commercial grades
- S-PVC K67 (pipes, profiles)
- S-PVC K57 (fittings, bottles, film)
- S-PVC K70+ (flexible, cable)
- Paste or emulsion PVC (coatings, leathercloth, flooring)
- CPVC (hot-water pipe, sprinklers)
- Recycled PVC (pipe cores, profiles)
- Bio-attributed PVC (mass balance)