The effect of fibre sizing and compatibilizer of polypropylene/poly(butylene terephthalate) blends on the mechanical and interphase properties of basalt fibre reinforced composites

The effect of basalt fibre sizing on the mechanical and interphase properties of fibre-reinforced composites was studied. Two different chemical preparations of the fibre surface (PBT-compliant and PP-compliant) were used. The polymer matrix was prepared from polypropylene/poly(butylene terephthalate) (PP/PBT) immiscible polymer blend and the effect of different compatibilizers on the composite properties was evaluated. SEM hints at improved fibre adhesion to the polymer matrix when a PP-compliant sizing is applied. SEM also reveals improved compatibilization effects when block copolymer instead of multiblock copolymer is used for the PP/PBT blend preparation. The pull-out test was applied to quantitatively evaluate the interface adhesion between the fibres and matrices. It showed a high value of the interfacial shear strength between basalt fibres modified with PP-compliant sizing and polymer blend compatibilized by block copolymer, thus confirming good adhesion. One possible explanation of such good mechanical properties can be related to the chemical interactions between functional groups, mainly maleic anhydride on basalt fibres and the polyolefin component (PP) of the polymer matrix.