Processing of fiber compounds in single‐screw plasticating units can cause fiber fracture. Attempts have been made to obtain large residual fiber length in finished components. Therefore, pultrusion compounded materials for extrusion and injection molding have been developed. Pellets chopped from pultruded strands, containing perfectly wetted fibers of uniform length, eliminate the need for the mixing operation in an extrusion compounder. The attempt to preserve the initial fiber length during processing reised interest in the origin of fiber attrition and in optimized processing parameters. Based upon the knowledge that fiber length breakdown takes place mainly during the process of screw plasticating, extrusion trials have been carried out under varied conditions. Fiber length distrubutions and fiber movement within the cross sections of the screw channel along the screw axis have been investigated. It has been shown that screw speed. Pressure and barrel temperature profile, in dependence on screw geometry, show a distinct influence on the residual fiber length. This information provides a description of the prevailing fiber attrition mechanisms and helps define the most suitable hardware and the corresponding adjustment of process parameters to preserve large residual fiber length.

Computer simulation packages have had success in predicting filling behavior in extremely complicated geometries. However, few packages offer the possibility of predicting the location and strength of weld lines. This work examines the sensitivity of Moldflow's weld‐line prediction algorithm to variations in material properties and processing conditions. Qualitatively, the algorithm correctly predicted the effects of changes in viscosity, density, and PVT relationship on weld‐line strength of a poly(methyl methacrylate). The algorithm is also successful in predicting the influence of variations in the injection time on weld line strength. However, the algorithm predictions for changes in the mold and die temperatures were at odds with the experiment. An attempt was made to correlate Moldflow's computed viscosities with the experimentally measured reduction in the strength in the weld‐line area. It was shown that a one‐to‐one relationship existed between these two quantities. Whereas the potential of using the viscosity to predict weld‐line strength has been demonstrated, further refinement of this new concept is needed and its validity for other systems has to be established.

Es wird gczeigt, daW die GroBenverteilung der Primiirpartikel von cntscheidendem EinfluW auf die FlieWcharakteristik von PVC-Plastisolen ist. Wegen der unterschicdlichen molekularcn Zusannnensetzung dcs I'VC in den grol3eren bzw. kleineren Teilchen ist die TeilchengroBe auch von EinfluW auf die Thermostabilitat. 0 musnuu paawepos u csoiicms vncmuy. l I B 9 Fca csoiicmsa nnacmuaoneii I I o~a 3 a~o pewamwee BjImHne pacnpeAeneHm IEPBWTHHX W C T H V no p a 3~e p a~ H a TeKyqecTb I I B X -n n a c~~a o n e l . BCjreACTBlle paannq~oro MoneKynRpHoro cocTaBa IIBX B KpynHbIx H Menmx sacmqax, paanrepb~ sacTHq TaKme OKa3blBaH)T BJILlRHne Ha l'epMOCTa6HnbHOCTb I I J I~C T H~O J I~~.T h e effect of the kind and size of PVC particles on the properties of plustisolsThe size distribution of primary I'VC particles is sliown to affect essentially the flow characteristics of plastisols. Due to the different molecular composition of PVC in larger and smaller particles t h e particle size affects also thermal stability.

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