The hot compaction of woven polypropylene tapes

In this paper we describe the hot compaction of woven polypropylene (PP) tapes. It is shown that under suitable conditions of temperature and pressure, successful compaction is achieved by selective melting of the PP tapes. Mechanical measurements, combined with morphological studies, show that good tape to tape bonding, and good interlayer bonding, are achieved using an optimum compaction temperature of around 182 degrees C, while retaining a significant proportion of the original PP structure. Differential scanning calorimetry studies have shown that the compaction temperatures employed to produce a homogeneous coherent material have a significant annealing affect on the crystalline structure of the original drawn tapes, with a large change in the crystal size and a small increase in overall crystallinity (accompanied by a small increase in sample density). The mechanical properties of the compacted PP sheets show a combination of low density and good stiffness and strength. (C) 1998 Kluwer Academic Publishers.