The incorporation of nano and micron-scale fillers to enhance the interlayer adhesion of hot compacted single polymer polypropylene composites

It is shown that the incorporation of micro and nanoscale fillers (e.g. carbon nanofibres, talc and nanoclay) dramatically improves the interlayer peel adhesion of single polymer polypropylene (PP) composites produced by the Leeds hot compaction process. This work is a combination of two previous studies which showed the advantage of incorporating either nanofillers into the PP tapes or interleaved unfilled films between the layers of fabric. In this study, we have explored different combinations of where the nanofillers are incorporated, with and without interleaved films. It has been shown that there is a synergism between the two approaches and that the incorporation of a filled interleaved film results in the best interlayer peel adhesion. This is of particular importance because it shows that the fillers do not need to be incorporated in the initial tapes. This allows cheaper processing, and the woven tapes to be drawn to a greater extent, thus resulting in higher mechanical properties of the final compacted sheet. Scanning electron micrographs show strong correlation between the observed damage of the peel surfaces and measured peel loads. It is shown that the peel load is dependent on the fraction of melted matrix at the interface and the degree of fibrillation in the tapes, which is promoted by the incorporation of the filler.