Tailoring of dual-interface in high tenacity PP composites - Toughening with positive hybrid effect

The study proves the feasibility of manufacturing injection moulded polypropylene composites reinforced with short rayon cellulose fibres of two selectively tailored fibre-matrix interfaces. The originally developed method relies on selective chemical grafting of two different polymer waxes onto the surface of cellulose fibres in order to obtain two different strengths of fibre-matrix interfaces in one composite. This selective tailoring of a dual-interface is meant to improve the notched impact strength without deteriorating of its flexural strength. Compatibilised fibres have a strong interphase, which conditions the transfer of strain from the matrix to fibres during deformation. Fibres tailored for a weak interface more efficiently hinder the crack propagation at crash. A 32% improvement of composite notched impact strength was achieved with merely a 5% deterioration of its flexural strength. Its specific properties are on the level or better than those of polypropylene counterpart reinforced with the same content of glass fibres.