A loss in part properties and service life is caused by thermal, mechanical, and thermo-oxidative stress during processing of thermoplastic materials. Process related thermal and mechanical stresses are inevitable. However, processing under exclusion of oxygen can reduce the thermo-oxidative stress. A lower thermooxidative stress can yield a higher transparency of optical parts, less reduction of average molecular weight for example in microinjection molding, and a longer service life due to less consumption of stabilizers during processing. For a cost-effective and gentle process it is important to know at which step of processing the polymer is exposed to thermo-oxidative degradation and where the oxygen comes from causing degradation. To study the local thermo-oxidative stress, an injection molding machine was encapsulated and run under local exclusion of oxygen. As reported in this article, thermo-oxidative degradation occurs in the plasticating unit due to oxygen from the surrounding air and oxygen dissolved in the polymer resin. POLYM. ENG. SCI., 48:717-722, Published online in Wiley InterScience (www.interscience.wiley.com). V V C 2008 Society of Plastics Engineers POLYMER ENGINEERING AND SCIENCE--2008 FIG. 6. Rheological behavior in dependence of oxygen exclusion for the high-stress level of process-parameter settings. FIG. 7. Elongation at break in dependence of oxygen exclusion for the low-stress level of process-parameter settings. FIG. 8. Elongation at break in dependence of oxygen exclusion for the high-stress level of process-parameter settings.

Polymer-bonded permanent magnets can be costeffectively produced by injection moulding of polymers with magnetic fillers. Rare-earth fillers (RE) such as NdFeB or SmCo have substantially better magnetic properties as compared with other permanent magnetic fillers. Nevertheless, they are highly reactive and susceptible to oxidation, and this leads to polymer degradation and filler oxidation during processing. This paper considers two different approaches to improving the stability of rare earth-filled compounds during processing: inert processing and filler coating.

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AbstrQct-Polymer Bonded Magnets can be cost effecth'ely produced by injection molding or polymers witb magnetic fillers.Rare-Eartb-fillers (RE) like NdFeB or SmCo in comparison witb