CRYSTALLIZATION KINETICS OF POLYPROPYLENE - PART 4 - EFFECT OF UNMODIFIED AND AZIDE-MODIFIED PET AND PA SHORT FIBERS

The effect of short polyethylene terephthalate (PET) and nylon 66 (PA) fibres, and their chemical treatment with an azide derivative, on the PP crystallization kinetics and thermodynamics has been investigated. Both fibres are effective nucleant agents for polypropylene (PP) crys tallization, giving rise to the phenomenon of PP transcrystallinity on their surface. However, the presence of azide groups on the chemical structure of the fibres produces a different effect on the PP crystall ization kinetics. Azide-modified PET fibres give rise to an additional increase of the global rate of the PP crystallization process, but in this case the transcrystalline development of the PP is not so sensib le as in the presence of the unmodified fibres. An opposite behaviour is observed with the azide-modified PA fibres. In general, it can be e stablished for the studied composites that the spherulitic development of the polymer matrix comes from an instantaneous and athermal nuclea tion whose growth is not constant. It is also suggested that transcrys tallinity and a good adhesion at the interface may take place independ ently one of each other. (C) 1998 Elsevier Science Ltd. All rights res erved.