Cadmium-based stabiliser systems have been used for many years due to their excellent performance qualities.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.
They are used in semi-rigid and flexible foil for products such as roofing membranes hoses, electrical insulation and in rigid applications for outdoor use such as window profiles and drainpipes.
Restrictions on use
Many regions have banned the use of cadmium in PVC for food contact materials and children’s toys.
In the European Union area, their use was phased out voluntarily as part of the PVC industry's Voluntary Commitment of 2000 (Vinyl 2010) due to concerns about toxicity and possible accumulation in the body. Since 2011 its used has been banned in the EU by entry 23 of annex XVII to REACH. The European PVC industry has put in place commercially viable alternatives to cadmium and lead-based compounds. They have been replaced by barium/zinc stabilizers in foils.
The International Cadmium Association (ICdA) is a non-profit association representing the interests of the world’s cadmium industry. Its Members include producers, processors, recyclers and consumers of cadmium metal, cadmium compounds, and products to which cadmium or its compounds have intentionally been added.
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