Heat stabilizer market ready for product changes-1

PVC (polyvinylchloride) is a versatile polymer, either rigid or plasticized to yield a flexible plastic. It requires, however, a heat stabilizer.

PVC is employed in many applications ranging from flooring, cable, and film made from plasticized vinyl to pipe, profiles, and sheets processed from rigid PVC.

However, PVC can only be processed in the presence of heat-stabilizing additives to avoid changes in the chemical structure caused by elevated temperatures and mechanical stresses.

Over the last decades lead (Pb) stabilizers were used to stabilize most rigid PVC worldwide except in North America, where tin (Sn) stabilizers dominated. Both systems show similar price/performance ratios; technically, they are incompatible with each other, cannot be recycled together, and thus are used exclusively in selective markets.

Now a trend toward stabilizers based on calcium (Ca) and zinc (Zn) as well as organic compounds is emerging. Use of these additives is mainly driven by voluntary commitments, such as the Vinyl 2010 initiative by the European PVC industry, started by key PVC industry players in 2000. It is a 15-year-program to meet the challenges of sustainable development and continuous environmental improvement throughout the European PVC sector.

Stabilizer systems based on calcium/zinc (CaZn) deliver some advantages over lead and tin stabilizers. They combine easy handling with good final product properties and excellent outdoor weathering performance. Like lead stabilizers, the are mostly offered as customized one packs. On the other hand, they are more product-specific, often requiring custom formulation for individual applications, when compared to lead-based stabilizer systems.

The cost of CaZn stabilizers is now similar to lead stabilizers. To get the complete picture, prices should be compared based on a similar unit length of final product. At first glance CaZn is more expensive, but delivers a higher yield. Since their introduction in the 1980s, the dosage of CaZn stabilizers has been reduced considerably and they are, therefore, often price-competitive to lead.

The use of the different stabilizer systems differs not only from region to region, but also from application to application.

Extruded PVC profiles are products with good physical properties that meet the most demanding economic and ecological requirements. Applications include window and door frames, shutters, cable ducting, siding, and gutters, to name a few.

In the profile sector, lead stabilizers are still widely used because of their good processability, favorable cost/performance ratio, and outstanding heat stability. However, CaZn stabilizers now possess a considerable market share in Europe since they have evolved out of expensive stabilizers based on metal soaps and polyoles to more elaborate systems comprised of effective inorganic acid scavengers and organic costabilizers.

(To be continued...)