ADDITIVES | POLYAMIDES
Right: Clariant is using
bio-derived feedstocks from Neste in its Exolit OP Terra additives
the Department of Mechanical Engineering at the University of Michigan-Dearborn in the US is looking at the damping behaviour of melt-compounded graphene or cellulose reinforcements in PA610.
Upcycling opportunities “Upcycling” of polyamides — recycling into perfor- mance applications — is possible through the use of a targeted combination of additives, including heat stabilisers, processing stabilisers, flow enhancers, nucleating agents, and others, according to additive supplier Brüggemann. These are needed because polymers that have already seen multiple heat histories and processing steps may not have the optimal viscosity for their next intended use. Appropriately selected additives can be used to either increase viscosity (to lengthen chains and increase molecular weight) or decrease viscosity. Chain-extension additives compensate for the
reduction in molecular weight resulting from degradation in use and reprocessing. Brügge- mann’s Bruggolen M1251 allows linear chain extension to occur during compounding and is claimed to be able to improve the mechanical properties of the recyclate to match those of prime material. Bruggolen M1253 is a smaller pellet size version of the same additive that is easier to dose during compounding. The company’s Bruggolen TP-M1417 additive,
meanwhile, can be used to shorten excessively long molecular chains in high viscosity polyamide waste such as films or cast nylon. This decreases the viscosity to bring the resins back to the injec- tion moulding viscosity range. The final viscosity can be accurately controlled by adjusting the quantity added. Compounds produced using this modifier “exhibit excellent mechanical properties and are suitable for the same applications as prime materials of similar viscosities. This removes the need to blend the recyclate with prime polymers,” says the company.
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A place for FRs A recent collaborative project between Clariant, Fraunhofer LBF and PINFA showed that glass-fibre reinforced polyamide containing Clariant’s HFFR Exolit OP1400 flame retardant could maintain a UL 94 V-0 rating after being recycled multiple times. The results showed that while mechanical proper- ties dropped after multiple cycles, the formulas containing OP 1400 were comparable to those containing no flame retardant, indicating that it does not negatively affect properties. The property decrease was rather attributed to loss of glass fibre length; flame retardancy was maintained. The results are important for companies looking to make use of production scrap and post-consumer recyclate, according to Clariant. PA recyclates containing bromine-based FRs
also fared well in studies. ICL-IP says it has investi- gated the suitability of its bromine-based flame retardants for production of PA66 compounds intended to be recycled. After five cycles of injection moulding followed by mechanical recycling, with each subsequent cycle comprised of a 50/50 blend of virgin and recycled compound, the PA66 compounds containing brominated FRs exhibited higher Izod impact strength initially and displayed a lesser decline on recycling compared to compounds containing a halogen-free FR,
IMAGE: NESTE
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