ADDITIVES | POLYAMIDES
Right: SEM image showing Chongqing PolyComp International’s new flat glass fibre reinforcement
that is activated after the melt-processing step. Teknor Apex puts a crosslinking additive into compounds to allow crosslinking by exposure of the final, moulded product to e-beam radiation in a secondary step, said Dr Hartmut Elsässer, Global ETP Technology Director for Teknor Apex Germany, in a presentation at AMI’s Performance Polyamides conference. When used in the E&E sector, crosslinking allows parts to retain their shape under higher use temperatures, which in some cases enables OEMs to switch from thermosets to crosslinked thermoplastics. This crosslinking method is now expanding from E&E to automotive, says Elsässer. In gear inserts for a motor cycle water pump, for example, crosslinked PA66 can replace metal to reduce noise. Although this method adds some complexity with its addi- tional processing step, he said e-beam radiation is a widely available service (it is used for industrial sterilisation of medical devices). One of Nexam Chemical’s Nexamite additives
offers the ability to remain inert during compound- ing but can activate crosslinking through post-pro- cess exposure to heat, either in a separate heat- activation process or in-service, such as in a hot engine component. The company cites the example of a glass-filled PA66, where the crosslinked formula showed a higher tensile strength after heat aging, corresponding to a longer service life at elevated temperatures.
Fibre options While glass fibre reinforcements would not normally be considered additives, the latest introduction from Chinese manufacturer Chong- qing Polycomp International Corp (CPIC) deserves a mention. It has introduced a family of novel glass fibers with a flat (rather than round) cross-section, which it claims facilitates higher fibre loadings and better mechanical properties. “The flat glass enhances thermoplastic process-
ing by lowering resin shear, providing better fluidity (increasing spiral flow), reducing friction and viscosity build-up, and lowering fibre entangle- ment and breakage since the flat fibres tend to flow in planar sheets like mica rather than rolling and tumbling like conventional round glass filaments,” the company says. “This in turn helps provide for a more isotropic dispersion and also allows higher fibre-volume fractions (FVFs) to be achieved with no other change because the fibres pack more closely.” The products are offered in E-glass form (chopped or milled) and are treated with sizing for use in various polymers, including polyamides.
CLICK ON THE LINKS FOR MORE INFORMATION: �
www.dowcorning.com �
www.ascendmaterials.com �
www.hpfminerals.com �
www.ensingerplastics.com �
www.ube.com �
www.dsmep.com (DSM) �
www.vertellus.com �
www.nexamchemical.com �
www.brueggemann.com �
www.addivant.com �
www.mitsuichemicals.com �
www.arkema.com �
www.teknorapex.com �
http://en.cpicfiber.com/ (Chongqing Polycomp)
PHOTO: CPIC
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