PVC STABILISERS | MATERIALS
weathering of these strips was performed for a total time of 4,000 hours. Weathering was simulated with standardised Xenon-arc lamps and the spray/dry cycle was run at 18 min/102 min intervals. Samples for colour reading were taken every 500 hours. These samples were comprehensively analysed, including heat stability measurement via the Congo Red test according to DIN 53381 (ISO 182-1), electron microscopic analysis of the surface and more.
Study results The results clearly indicated that in dark-coloured PVC applications, the finely tuned formulation of
the PVC matrix – with both heat stabilisers and TiO2 pigments – is key to significant improvement of the weathering resistance of the final product. This fine tuning is highly dependent on the customer’s specific set-ups in terms of machinery tooling and raw materials. The fine tuning involves optimising the levels of critical stabiliser components such as acid scaven- gers, co-stabilisers and internal and external lubricants. In dark-coloured applications, the super durable grade would be more appropriate due to its
improved weathering performance and lower tint strength.
With specific premium calcium-based grades
providing superior heat and light stability, the weathering performance is further enhanced. This finding can be better explained when taking into account the decrease of Congo Red values demonstrating the ongoing PVC degradation during weathering. In turn, the higher thermostabil- ity achieved with the calcium-based premium grade shows the effectiveness of this specific additive system not only in processing but also in outdoor service. For applications with reduced or no weathering
requirements, other specific stabiliser grades are available which are more cost-effective. Lead-based stabilisers, which have not been used in Europe since 2016 according to VinylPlus, have often been attributed better weathering properties than calcium-based stabilisers – but the study shows that this is no longer the case.
n Dr Jörg Fröhlich is technical product manager for PVC Additives at Baerlocher �
www.baerlocher.com
www.kraussmaffeiberstorff.com
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Engineering Value
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