Caractérisation des longueurs de fibres dans différents types de composites polypropylène-fibres de verre courtes—2 éme partie. Etude des matériaux après injection

Abstract

The aim of this work, dealing with injection moulding of short glass fibres reinforced-polypropylene matrix composites, was to investigate the interrelations which can exist between: • •|some matrix and fibres-size composition and injection moulding parameters • •|fibre length distributions in injection moulded test pieces • •|associated mechanical characteristics. We have shown that: 1. (1)|when the different unreinforced polypropylenes used as matrices have quite identical molten state viscosities, they have little influence on the glass lengths distributions in injection moulded pieces 2. (2)|on the opposite, the glass fibres size composition can exert a strong influence on fibres lengths distributions in injection moulded pieces: the incorporation of aminosilane + anhydridmaleic-polypropylene modified coupling agent in the fibres size always involves an increase of mean fibres lengths and a decrease of the fibres lengths scattering 3. (3)|the alteration of some injection parameters like screw speed, barrel temperature or back pressure level always involves expected changes of mean fibre lengths but: ◦ •|when the fibres are sized without coupling agent, a fibre length reduction is always associated with a decrease of mechanical characteristics ◦ •|on the opposite, when an aminosilane + anhydrid-maleic-polypropylene modified coupling agent is incorporated in the fibre size, the interrelation between mean fibre lengths and mechanical characteristics is far less clear. This phenomenon has been interpretated in terms of structural changes at the interface between polypropylene matrix and glass fibres.