Suspension PVC (S-PVC) is sold mainly by its K-value. Choosing the right K-value is the first step in matching a resin to your product and process.
What the K-value is
The K-value (Fikentscher K-value) is calculated from the viscosity of a dilute PVC solution. It is an indirect measure of the polymer's molecular weight. A higher K-value means longer polymer chains: stronger, tougher products, but a resin that needs more heat and work to process.
Typical K-values by application
- About K57–60: injection-moulded fittings, bottles and some rigid film, where easy flow matters
- About K64–68: rigid pressure and drainage pipe, window and door profiles
- About K70–71: flexible products with plasticiser, such as cable insulation, hose and flexible film
These are typical ranges. Your formulation, machine and product standard decide the exact grade.
K-value and SG grade names
Many suppliers also use SG grade names. As an approximate guide: SG-3 is around K70–72, SG-5 around K66–68, SG-7 around K60–62 and SG-8 around K55–59. Always check the K-value on the technical data sheet rather than the grade name alone.
Other properties to check
- Bulk density: affects dry-blend handling and extruder output.
- Porosity and plasticiser absorption: important for flexible PVC.
- Residual vinyl chloride monomer: regulated in many markets, especially for food-contact and drinking-water uses.
- Volatile content, contamination and colour: affect processing and appearance.
Suspension vs emulsion PVC
Suspension PVC is the general-purpose resin for pipe, profile, film and cable. Emulsion (paste) PVC is a different type used for plastisols, such as coatings, flooring and synthetic leather. Make sure your enquiry names the type you need.
What to send for a quote
- K-value range, or your current grade and its data sheet
- Application and process (pipe, profile, film, cable)
- Limits your market requires, such as residual vinyl chloride
- Quantity, packing (25 kg bags or big bags), destination port and Incoterm