Back to All Technical Guides Technical Review Passed
Extrusion Engineering5 min read•2026-08-27
PVC K-Value Guide: Choosing Between K57, K65, K67, and K70
Extrusion Technical Desk
Birka PVC Compounding Consultant
The K-value of PVC indicates the degree of polymerization and molecular weight of the resin. Selecting the correct K-value is essential to balance extrusion motor load with finished part impact resistance.
1. The Fikentscher K-Value Scale Explained
Calculated from dilute solution viscosity measurements in cyclohexanone according to ISO 1628-2, the K-value ranges from K50 (low molecular weight) to K80 (high molecular weight).
Higher K-values yield superior tensile strength, elongation, and impact toughness, but require higher processing temperatures and heavier shear torque on the extruder screws.
| PVC Grade | K-Value Range | Typical Conversion Process | Primary Industrial Applications |
|---|---|---|---|
| PVC K57 (S-57) | 56 – 58 | Injection Molding / Calender | Pipe fittings, rigid sheets, electrical junction boxes |
| PVC K65 (S-65) | 64 – 66 | Extrusion & Siding | Window profiles, rigid cladding, technical profiles |
| PVC K67 (S-67) | 66 – 68 | Twin-Screw Extrusion | Potable water pipes, sewage pipes, conduit trunking |
| PVC K70 (S-70) | 69 – 71 | Plasticized Extrusion | Wire & cable insulation, flexible hoses, waterstops |
Related In-Stock Materials in Sulaymaniyah
Need Batch Pricing for These Resins?
Receive an official stamped commercial proforma invoice within 24 hours.