additives | PVC
The sustainability principles of The Natural Step (TNS) framework In a sustainable society, nature is not subject to systematically increasing: l concentrations of substances extracted from the earth’s crust; l concentration of substances produced as a by-product of society ; l degradation by physical means (deforestation, draining of water tables, etc.);
l In that society, there are no structural obstacles to people’s health, influence, competence, impartiality and meaning. ❙
www.thenaturalstep.org
collected by ESPA, the European Stabiliser Producers Association). Today, despite lead stabilisers having been phased out recently in Europe and even longer ago in North America – these types still account for more than half of all global consumption and there also remains a significant amount of barium-cadmium types in use. Forecasts indicate that despite efforts by companies such as Reagens and other ESPA members, even more lead stabilisers will be consumed ten years from now.
Right: PVC pipe producers can benefit from organic
hydrotalcite stabilisers,
which prevent the formation of onium salts that cause
discolouration
New opportunities for organics At another leading stabiliser producer, Chemson, Bernhard Pelzl, Head of R&D used his opportunity at the PVC Formulation conference to talk about new developments in organic stabilisation systems for flexible applications. He said the prospects for organics are improving in the wake of the withdrawal in Europe and North America of lead-based systems, as well as limitations in some countries on the use of mixed-metal and tin-based types. Stabilisers have to perform three main roles, Pelzl said: substitution of labile chlorine; neutralisation of
hydrogen chloride; and elimination of polyenes. Zinc soaps are frequently used to substitute labile chlorine, but their acidic character dramatically decreases heat stability. An organic stabiliser, 1,3-dimethyl-6-aminou- racil – commonly known as DMAU – is a highly effective alternative. Organic stabilisers containing sodium perchlorate
assist this substitution. They also eliminate the polyenes that can be created when PVC degrades, providing an alternative to carboxylic acids from metal soaps in mixed metal stabilisers. Polyenes cause discolouration in PVC. Depending on their molecular weight, this discolouration can range from yellowing through to dark brown. Sodium perchlorate is very effective at increasing the dynamic heat stability of PVC. When it comes to neutralising HCl, the traditional
products include calcium and barium soaps. However, organic systems containing hydrotalcite minerals are now well established in rigid PVC formulations for applications such as pipe and they are gaining in
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PHOTO: SHUTTERSTOCK
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