Clear rigid and semi-rigid film is used for blister packs, trays and clear boxes. In products like these, small defects show immediately: a yellow tint, haze or specks will be rejected by the customer. Stabilizer choice is one of the most important factors.
Tin stabilizers (methyltin mercaptide)
Tin stabilizers are very efficient at low dosage and give excellent early color and clarity. They are liquid, which makes dosing more accurate. Stannova ST-810 is an example, dosed at 0.8–1.7 phr for rigid film and sheet. Tin stabilizers contain no lubricant, so they need a separate lubricant package, and they must not be mixed with lead because that causes sulfur staining.
Clear CaZn grades
CaZn is the lead-free and tin-free option. Grades designed for clear film, such as Calzora CZ-810, give good clarity with low plate-out, dosed at 1.5–3.0 phr. CaZn is often chosen when the customer or target market asks for a tin-free system.
Other components that decide clarity
- K57 resin with low melt viscosity for good fusion at lower temperatures.
- An MBS impact modifier with a refractive index matched to PVC, such as Endura MB-810, so the film stays clear with low stress whitening.
- Compatible lubricants and processing aid, to avoid plate-out on the calender rolls.
For food packaging
Food-contact suitability depends on the complete formulation and the regulations of the target market, not on one ingredient. Discuss your needs with our team before production, so the formulation is built with the right materials from the start.