Calcium Zinc Compound Stabiliser

About This Product

Calcium zinc compound stabilisers are one-pack systems built on calcium and zinc carboxylates with organic co-stabilisers, antioxidants and lubricants pre-blended in. They exist because lead and cadmium stabilisers, which performed well and cost little, are now excluded from most markets on toxicity grounds. The chemistry is a division of labour. Zinc soaps substitute the labile allylic chlorines that start dehydrochlorination, which gives good initial colour, but the zinc chloride produced is a strong Lewis acid that catalyses the very degradation it was added to prevent. When the zinc is exhausted the compound blackens abruptly, an effect known as zinc burn. Calcium soaps and the organic co-stabilisers in the pack exist to capture that zinc chloride and to regenerate the zinc soap, converting a sudden failure into a gradual one and extending long-term stability. Because the balance of zinc, calcium and co-stabiliser has to be matched to the polymer, the processing temperature and the residence time, these products are sold as application-specific series rather than as one grade. The 21 series is for medical PVC including food packing, medical tube and toys; the 31 series for soft and semi-rigid PVC such as wire and cable, calendering film and artificial leather; the 41 series for small and medium pipe and water pipe; the 51 series for rigid injection moulding such as fittings; the 61 series for high shear, high speed extrusion profile; the 71 series for foam; and the 81 series for transparent product.