MATERIALS | PVC ADDITIVES
Reagens has developed a stabiliser range that protects dark-coloured PVC from degradation
Source: Reagens
on colour changing during exposure. Calcium and magnesium hydroxides, and silicon dioxide, actually made colour degradation worse. The researchers found that ‘well-balanced’ acid scavenger packs provided stronger protection. “The design of the appropriate stabiliser
formulation still requires a complex choice of ingredients and needs several laboratory and real field tests,” the researchers concluded. Prior to this, the company tested two of its tin- based stabilisers and three calcium organic stabilisers (COSs), each with 7 and 9 phr of titanium dioxide concentration. Each sample was exposed five times, each for four years, in a severe climate. The tests showed a similar performance for all stabilisers, with “COS technology proven to be a valid and, in many instances, outperforming alternative to tin-based stabilisers”, said the company.
Tin replacement Tin-based stabilisers for PVC, predominantly used in rigid, often transparent, calendered film and foamed profiles and sheets, have long been the focus of regulatory bodies due to environmental concerns. Calcium-based stabilisers are seen by many as a viable alternative and are already being utilised in many applications such as plasticised film or rigid compact and foam sheet extrusion. Conventional tin stabilisers offer limited lubrication but provide good transparency, heat stability, and high transparency. All these properties and more need to be provided by the alternatives. German additive manufacturer Baerlocher has developed various calcium-based grades for rigid calendered film, such as Baerostab NT 1883 P or Baerostab NT 1929 P-series, which can cope with demand for high transparency, good initial colour, and maintaining a stable calendering process due to adjusted low lubricity. For foam profile and foam sheet formulations used in continental Europe, calcium-based stabiliser systems are designed in a conventional way as they are used in rigid PVC
30 PIPE & PROFILE EXTRUSION | Winter 2024
profile extrusion. Care must be taken when fine-tuning co-stabiliser systems and lubricants for foam extrusion to achieve proper surfaces and colour. Not all aspects are related strictly to stabilisation, and the company is a big advocate of making necessary formulation adjustments after close communication with converters. At NPE 2024 in Florida in May, US-based performance additive producer SI Group show- cased Weston 705, a phosphite stabiliser free of nonylphenol which can be used in a variety of polymer systems including PVC. Weston 705 reduces both plate-out and gel formation by a factor of ten, and has been developed as an alternative to TNPP or for use in applications with nonylphenol restrictions. Adam Watson, senior sales director, polymer solutions – North America at SI Group, said: “Our presence at NPE underscores our dedication to driving positive change within the plastics industry, advancing towards a more sustainable and circular future.” As in other areas of plastic production and manufacturing, sustainability is now considered a high priority in PVC formulation and a lot of PVC materials such as building materials, film, and wire and cable, are being developed in accordance with these concepts. Japanese additive manufacturer Adeka has long been involved in the development of environmentally friendly stabilisers to meet these increasing requirements and offers Ca-Zn system stabilisers as an alternative to lead-stabilis- ers, such as ADK STAB RX-300 series for fittings, and ADK STAB RUP series for wire and cable, which are said to provide excellent heat stability, colour stability, and processability, as well as possessing other important mechanical properties. The company says recently it has also focused on the development of tin-replacement stabilisers, traditionally said to be difficult to replace due to their excellent stability performance, and claims its latest offering can provide similar levels of trans- parency, colour stability, heat stability, and heat
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