The use of calcium/zinc stabiliser systems has been  common in PVC applications for over 25 years.

These materials are generally based on metal carboxylatesand will sometimes incorporate other elements to boost performance such asaluminium or magnesium. Because the heat stability in some applications mayrequire some enhancement when using calcium/zinc, organic co-stabilisers willalso often be added to this type of formulation. These materials includepolyols, epoxydised soya bean oil, antioxidants and organic phosphites.

Properties and Applications
Because of the characteristics of calcium/zinc stabilised materials they arewidely used in many flexible and rigid PVC applications. This type ofstabilising system can give products which have a high degree of clarity, goodmechanical and electrical properties, excellent organoleptic properties andgood outdoor weatherability. As a result, calcium/zinc stabilisers have beenincorporated and established in a wide range of applications as shown in tabletwo. These include toys, healthcare products, such as blood bags, semi-rigidand flexible foil for food packaging, bottles for potable water, as well as forpotable water pipe.

The performance of more recent developments in calcium/zinc stabilisers alsomakes them potential technical alternatives to most other stabilising systems,including lead and barium/zinc. As a result of the European PVC industry’scommitment to progressively phase out heat stabilisers based on lead compounds,considerable development work has been carried out on new, improved systems forapplications including cable covering, pipe and window profile and many ofthese are have been in commercial use for several years. These newer forms ofcalcium/zinc stabiliser are in general more complex and expensive than thetraditional soaps mainly because of the specialised co-stabilisers required tomeet the specific requirements of these applications. The rate of introductionof such stabilising systems was slowed down by the extensive evaluation workrequired and the need for acceptance by the specifier. So far, the penetrationof calcium/zinc stabilisers in these three sectors is complete in drinkingwater pipes and cables but not yet in other pipes and profiles. Sales offormulated Ca based stabilizers in Western Europe andTurkey,including Ca/Zn, have increased from 18 kt in 2000 to 80 kt in 2011. Furthergrowth is expected as a result of the progressive phasing out of lead-basedsystems. In the sector of flexible foils where the main stabiliser used is abarium/zinc soap, substitution by calcium/zinc materials is also taking placealthough, again, there are technical issues which need to be overcome.

Applications for Stabilisers – European Market

++ Major use + Minor use (+) Occasional use (1) Used forpotable water pipe (2) Used as a stabiliser/’kicker’ for foamed layers inthese products

Safety, Health and Environmental Issues
Inherently calcium/zinc stabiliser systems incorporating the proven range ofco-stabilisers have low toxicity or are regarded as non-toxic.
Calcium/zinc salts of any of the acids in the EU Additives Directive areapproved for food contact use, although specific approval would depend on theco-stabiliser incorporated into the stabilising system. Solid calcium/zincstabilisers have to meet the general requirements for dust emissions in theworkplace although dust-free forms are readily available. Zinc is an essentialelement to human activity and health and has been the subject of various riskassessments. The conclusion of these has been that there are no risks to humanhealth or the environment arising from the use of zinc stearate in PVC heatstabilisers.