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polyamides | Additives


Figure 2: Colour properties of Addworks 568 compared to PS168 phoshinate in glass reinforced PA66


Source: Clariant


LXR 568. The latter is a brand new product, which is only now beginning to be sampled by customers. Emilie Meddah, in Clariant’s plastics additives technical marketing unit, says it provides very good hydrolytic stability, improved colour retention and high resin protection at low addition rates. The additive is seen as a higher-performance alternative to widespread PS 168 phosphonite additives, including Clariant’s own Hostanox P-EPQ. These have been available on the market for many years but are all quite sensitive to moisture. The company says the new LXR 568 grade is suitable for a wide range of other polymers beyond polyamides (see Figures 2 and 3).


The LXR 701 product was unveiled at the last K show in 2013 and was developed to improve fl ow of polyamide glass-fi lled compounds, enabling (once moulding condi- tions are optimised) a drop of as much as 30°C in processing temperature and a cycle time reduction of up to 15-20%. Moulded parts are also said to show a better surface appearance and improved dimensional stability. Meddah says several customers are now close to concluding their own tests on the additive.


Silicone solutions


Figure 3: Hydrolysis resistance of Addworks 568 compared to PS168 phoshinate determined by measurement of breakdown product DTBP (di-tertio-butyl-phenol)


Source: Clariant


strength and mechanical performance. Its portfolio con- tains chain-extenders, long-chain branching agents and products for cross-linking. Company CTO Dane Momcilovic highlights the Nexamite product range as suitable for modifi cation of polyamides (it is based on pentaerythritol triacrylate (PETA), a multifunctional alkynyl-based product). Momcilovic says one particular grade, Nexamite A56,


effi ciently increases the complex viscosity and the melt strength by up to two to three orders of magnitude in certain polyamide resins (especially in amino-terminat- ed polymers) in under one minute at temperatures above 200°C. The additive can be used in many polyamide compounding and extrusion processes with existing extrusion equipment. “For standard type polyamide resins, Nexam has developed novel effi cient formulations based on A56 and various booster and catalyst systems,” he says. Clariant highlights two grades in its AddWorks series for PA modifi cation applications – LXR 701 and


22 COMPOUNDING WORLD | February 2016


Dow Corning is taking its own route to improving hydrolysis resistance. It is developing a silicone-based masterbatch to increase the hydrophobic nature of polyamides, principally 6 and 66 types. Internal trials are said to have shown signifi cant benefi ts and the company is now initiating customer trials. Full commer- cialisation is likely to occur around the end of 2016. Moisture pick-up can have a major effect on


modulus, according to Christophe Paulo, Dow Corning’s global segment leader for plastics. He says a standard PA in the dry-as-moulded state may display a modulus of 9 GPa but, once it has been conditioned and picked up around 3% water, the modulus may fall by more than 40%. The Dow Corning masterbatch, added at up to around 5%, reduces water uptake and improves overall mechanical properties in the conditioned state by 25-30% at the very least, he claims.


Some of the plasticizing effect of the water is lost, so


impact strength will be reduced, but Paulo sees the product making a key difference in terms of PA application.


“This is a game changer, it could mean that proces-


sors would not need to use polyphthalamides in place of standard polyamides – in applications where thermal resistance is not critical – or add maleic anhydride grafted PP, which has a signifi cant drawback in reducing DTUL,” he says. Likely applications include compounds for automotive engine compartment components, HVAC systems, and electronic enclosures.


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