Luffa cylindrica fibres/vinylester matrix composites: Effects of 1,2,4,5-benzenetetracarboxylic dianhydride surface modification of the fibres and aluminum hydroxide addition on the properties of the composites

In this work we used a sequence of organic extraction and chemical modification treatments in order to increase the compatibility between the mat fibrous of the Luffa cylindrica ripe fruit and the vinyl ester resin for composites preparation. As observed from SEM and suggested from XRD analyses, these sequential treatments did not degrade the L. cylindrica fibres preserving their potential use as a reinforcement. The FTIR analyses and the conductometric titrations showed evidences of interactions between the fibres and the dianhydride. A fibre mass ratio of 15% was used for composites preparation decreasing the density of the composites at ca. 45% when compared with the vinylester matrix. The TG analyses showed that the aluminum hydroxide addition in the matrix increases the thermal stability of the composites. The DMA showed that the fibres did not influence the matrix cure kinetics, and a biphasic system was formed during pre-curing under environmental conditions. The tensile and Charpy impact strength tests showed an increase of the strength of the composites when compared with the matrix. The best results were obtained for PMDA treated fibres/vinyl ester matrix composites, which showed an increase of ca. 30% for tensile strength and 250% for impact strength.