Stabilisers are essential to PVC
Therefore, use of stabilisers is essential to prevent the chain reaction of decomposition. They can also increase PVC’s resistance to daylight, weathering and heat ageing and have an important influence on the physical properties and the cost of a formulation. They are invariably supplied in the form of application-specific blends of which the main constituents are metal soaps, metal salts and organometallic compounds. The choice of heat stabiliser depends on a number of factors including the technical requirements of the PVC product, regulatory approval requirements and cost.
Heat stabilisers used in a formulation are usually combined with co-stabilisers that are organic materials such as polyols or epoxidised esters. They provide an additive synergistic effect, and, in the case of certain heat stabilisers, an enhancement of overall stabiliser performance.
Lead-based systems have been voluntarily phased out and replaced with CA/Zn or CA/organic stabilisers within Europe under the Vinyl 2010/VinylPlus voluntary commitments of the PVC industry.
The majority of tin (Sn) stabilisers are used for rigid packaging films, roofing and transparent rigid sheets for construction applications. The major metals contained in stabilisers are barium (Ba), calcium (Ca), zinc (Zn) and tin (Sn). Ba-Zn and Ca-Zn stabilisers are used under the form of metallic salts such as stearates, while Sn stabilisers are used under the form of organic tin (dialkyl tin compounds).
Stabiliser fact table
|Stabiliser type||Principal metal||Metal content (%) packaging||In PVC formulation other|
|Lead compounds||Lead||Not used||-|
|Barium/zinc compounds (only for plasticised applications)||Barium zinc||Not used||~0.1 <0.2|
|Calcium/zinc compounds||Calcium zinc||0.1 <0.2||<0.5|