Intrinsic Viscosity (IV) — Reading PET Quality
IV is a measure of average molecular weight for polyesters like PET. Higher IV means longer polymer chains and is essential for bottle- and fibre-grade quality.
What it measures
Intrinsic Viscosity (IV) expresses the average molecular weight of a polyester such as PET, reported in dl/g (for example 0.78–0.82 dl/g). Longer polymer chains give a higher IV.
Why it matters
IV is the single most important quality figure for recycled PET. Higher-IV material has the chain length needed for bottle- and fibre-grade processing; lower-IV material suits sheet and strapping. Processing history and drying affect IV, so consistent IV is a sign of well-controlled recycling.
On Sinox products
PET recyclate at Sinox states its IV where applicable, alongside form (flakes or regranulate) and any food-contact suitability. See the PET polymer guide for the full picture.
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