Description:
<jats:title>Abstract</jats:title><jats:p>Specimens of unmodified polypropylene have been manufactured using extreme adjustings of injection moulding machines and extruders. After artificial weathering, distinct relations of ageing processes to thermal and mechanical production parameters were found, which are not influenced by different melting temperatures. It can be started in particular, that during injection moulding a larger shear stress (resulting in more distinct orientation) results in
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<jats:list-item><jats:p>a greater change in residual stresses</jats:p></jats:list-item>
<jats:list-item><jats:p>an earlier gloss reduction</jats:p></jats:list-item>
<jats:list-item><jats:p>a shorter initial period before cracking.</jats:p></jats:list-item>
</jats:list></jats:p><jats:p>During extrusion a lower cooling rate (resulting in a coarser structure) leads to
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<jats:list-item><jats:p>a greater change in residual stresses</jats:p></jats:list-item>
<jats:list-item><jats:p>an earlier and more distinct gloss reduction</jats:p></jats:list-item>
<jats:list-item><jats:p>an earlier loss of ultimate strain.</jats:p></jats:list-item>
</jats:list></jats:p><jats:p>It remains unknown, whether
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<jats:list-item><jats:p>these relationships will be similar with other thermoplastic materials than PP</jats:p></jats:list-item>
<jats:list-item><jats:p>these relationships appear to the same relative extend with stabilized systems</jats:p></jats:list-item>
<jats:list-item><jats:p>it may be advantageous, to use the observed effects by adjusting the injection moulding and extrusion machines in a special way.</jats:p></jats:list-item>
</jats:list></jats:p><jats:p>It seems to be significant to do more research work in this field.</jats:p>