ADDITIVES | PVC
Completing the new introductions, Blendex SS400 further extends Galata’s polymer modifier product range. It is said to be suitable for use in rigid PVC compounds for demanding applications where high Izod impact resistance is required, such as rigid calendered sheet and profile compounds. In addition to its ability to deliver high Izod impact resistance at lower loadings, the product is also said to maintain very good drop dart impact and gloss characteristics.
Weathering effects It is well known that PVC undergoes thermal degradation and photo degradation due to exposure to natural sunlight and that this weather- ing effect depends on temperature, irradiance and humidity of specific geographical conditions, according to Reagens. A white window profile, for example, if not
Figure 1: The latest one-pack Ca/Zn stabilisers from Reagens are formulated to prevent chalking of dark coloured weatherable PVC articles Source: Reagens
Figure 2: ISO 5660 smoke production rate comparison of a typical PVC formulation containing ATO (blue) and an equivalent containing Reagens NT8004 FR (grey) Source: Reagens
correctly formulated could turn yellow in a rela- tively short period of time. On the other hand, a brown or green PVC shutter could easily whiten due to the phenomenon of “chalking”. This chalking effect is the result of a complex series of reactions that together cause strong oxidation and damage of the surface through creation of micro cracks and holes, which scatter incident light. Reagens has developed a new range of one-pack Ca/Zn stabilisers formulated to prevent chalking of dark coloured weatherable PVC articles over extended periods of exposure (Figure 1). One of the keys to the success of PVC, particu- larly in building and construction, is its outstanding fire performance; the polymer is difficult to ignite and displays low flammability, a high tendency of self-extinction, low flame spread, and quite low heat release rate. But it is still often necessary to add flame retardants and smoke suppressants, especially in unplasticised articles. One of the most common flame retardant system components used in PVC is antimony trioxide (ATO). However, antimony reserves are in the hands of just a few players, many of which are in China. For that reason, antimony has been considered a critical raw material in the European Union, and it is one of 35 mineral commodities considered to be critical to the economic and national security of the United States. “In the European Union, ATO is also under the
Figure 3: Dynamic thermal stability tests carried out in a Brabender Plasti-Corder (chamber temperature 180°, rotor speed 50 rpm, sample weight 65 g) comparing PVC containing 1phr of tin stabiliser with 0.7phr of Reapak B-NT/7222 booster (top) and a formulation with 3.5phr of Reapak TU/1900 COS stabiliser. Sample numbers refer to time (minutes) Source: Reagens
52 COMPOUNDING WORLD | June 2022
eye of ECHA and the possible change of the classification can be a weak point for [the] PVC value chain,” says Gianluca Sarti, R&D Manager at Reagens (ECHA currently classifies antimony trioxide as Suspected to be Carcinogenic). “What Europe learnt, particularly in these last
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