Cadmium-bearing stabilisers are used to retard the degradation processes which occur in polyvinylchloride (PVC) and related polymers on exposure to heat and ultra violet light (sunlight). These stabilisers consist of mixtures of barium, lead and cadmium organic salts, usually cadmium stearate or cadmium laurate, which are incorporated into the PVC before processing and which arrest any degradation reactions as soon as they occur. They ensure that PVC develops good initial colour and clarity and allow high processing temperatures to be employed. They also ensure a longer service life for the PVC. Cadmium-bearing stabilisers also allow higher temperature processing for some PVC resins and impart dynamic and thermal stability to resins processed in calendering (sheet rolling) operations.
Barium/cadmium stabilisers typically contain between 1 and 15 per cent cadmium and usually constitute about 0.5 to 2.5 per cent of the final PVC compound. No alternative stabilisers offer all of the advantages of barium/cadmium formulations and they are incorporated into PVC used, for example, in rigid profiles for window and door frames, water and drain pipes, hoses and electrical insulation.
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