PROCESSING OF SINGLE-POLYMER COMPOSITES USINGTHE CONCEPT OF CONSTRAINED FIBRES

摘要

Nowadays the major trends in polymeric materials focuses on simple mono-componentsystems, rather than on complex polymer blends. An important reason for this is recyclability. Theconcept of ‘overheating’ a fibre upon constraining is one of the known methods for manufacturing singlepolymer composites. This concept was validated on two categories of semi-crystalline polymers: thedrawable (I.e. isotactic Polypropylene) and the less drawable ones (I.e. Polyethyleneterephalate andPolyamides). In case of I-PP it was shown that a draw ratio higher than 10 is required in order to obtain a20°C shift of the melting temperature and therefore a sufficiently wide processing window. The effect ofthe post-drawing temperature on the ‘overheating’ behaviour of I-PP was also investigated. It wasconcluded that the drawing temperature should be optimised in order to avoid relaxation processes in theamorphous phase while at the same time to induce orientation and improvement of the crystals in terms ofsize and perfection. Less drawable polymers give only a small shift in melting temperature, thus a smallprocessing window. This is mainly due to the low degree of chain-extension, -unfolding of this categoryof polymers.