钙锌复合稳定剂 — Frequently Asked Questions

Zinc soaps protect early colour by reacting quickly with unstable chlorine in PVC, but the zinc chloride they form can cause sudden blackening. Calcium soaps react with that zinc chloride, regenerating the zinc soap and neutralising hydrogen chloride, which gives longer-term stability. Co-stabilisers such as polyols and hydrotalcite widen the window further. Neither metal alone gives good colour and long-term stability together.

Zinc burning is the sudden blackening of PVC when zinc chloride builds up faster than the calcium soap and co-stabilisers can neutralise it. It usually appears after long residence time, at die hang-up points or when regrind is overworked. It is avoided by choosing a grade with enough calcium and co-stabiliser for your heat history, keeping the zinc level appropriate, and cleaning out stagnant areas in the extruder and die.

A one-pack blends the stabiliser, co-stabilisers, lubricants and sometimes processing aids and antioxidants into a single product, so the processor adds one ingredient at a fixed dosage. It reduces weighing errors and simplifies stock. The trade-off is less freedom to adjust the lubricant balance separately, which is why grades are designed for a particular process, such as pipe, profile or cable.

They replace them, but not one-for-one. Lead systems are strongly lubricated and very tolerant, while calcium-zinc systems need a different lubricant balance and often a slightly different processing temperature. Expect to adjust dosage, lubricants and sometimes the processing aid, and run trials on your own extruder. Once set up, calcium-zinc compounds give comparable pipe and profile performance.

Calcium-zinc systems are the usual choice for food-contact PVC because their main components have a favourable toxicity profile, but suitability depends on every component in the exact grade. Ask for a declaration of compliance against the plastics food-contact regulation that applies in your market, with any restrictions and migration limits, and confirm it covers your intended food type and conditions of use.

Each series is formulated for a product family, and the differences lie in the metal ratio, co-stabilisers and built-in lubricants. A pipe grade needs strong external lubrication for high output, a profile grade needs good weathering and surface finish, a cable grade needs electrical properties, and a foam grade must work with blowing agents. State your process and product so the grade can be matched.