Polarized light microscopy was used to investigate the presence of preferred molecular orientation in the LCP phase of PPS/LCP blends after injection moulding. Normal birefringence effects appeared to be complicated by artifacts due to sample preparation and by the complex nature of polarized light transmission through a multicomponent sample. It was found, however, that, during low-temperature cutting of optically transparent thin sections on a standard microtome, individual LCP particles could be separated from the PPS matrix, and their birefringence analyzed separately. Preferred orientation was detected only in LCP fibrils which dominated in skin regions, but not in droplet-shaped particles which had formed in core regions. Quantitative measurements indicated that the molecular orientation of the fibrils increased linearly with their length-to-diameter aspect ratios which ranged from 15 to 50. Even for the highest aspect ratios, however, the degree of orientation was always less than that which could easily be introduced into pure LCP thin-film samples by manual shearing.

The phenomenon of transcrystallization was studied at the interface of UHMWPE fibers embedded in an HDPE matrix. It was hoped that epitaxial crystallization in such model composites could eventually be used to improve adhesion between these high-strength fibers and the thermoplastic matrix material. Matrix crystallization was induced and accompanied on a specially designed hot stage which made the crystallization front advance slowly along a thermal gradient. Transcrystalline interfacial layers were observed without regard to temperature conditions, but with widely varying dimensions. Lamellar resolution within these layers was achieved by low voltage scanning electron microscopy, and the very beginning of transcrystallization was observed in sample areas where UHMWPE fiber segments were only partially embedded into the HDPE matrix. Lamellar alignment on the fiber surface indicated that transcrystallization in this system was associated with epitaxial nucleation.