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Today, the ‘mixed metals’ group covers all solid
stabilisers based on a combination of metal carboxylates
(solid salts) and costabilisers which support the overall
performance.
Solid metal salts are often referred to as metal "soaps"
and were already being used as early as 1934 to stabilise
PVC. Today a variety of metals, like calcium, magnesium
and zinc are used.
Driven by the perception of enhanced health and environment
properties, mixed-metal stabiliser systems (often referred
to as CaZn or Calcium-Zinc) have been the subject of much
study by European stabiliser manufacturers. To match the
superior thermal properties of lead stabilisers, co-stabilisers
which have been sanctioned for indirect food contact are
added to the mixed-metal stabilising system. Today, the
mixed-metal systems are capable of covering the whole area
of PVC applications. In some cases such as white window
frames excellent colour stability weathering results have
been obtained both in long-term testing and from practical
experience.
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