ABSTRACT

Perpendicularly arrayed and size-controlled nanocylinders have been prepared by simply blending an asymmetric polystyrene-block-polyisoprene-block-polystyrene triblock copolymer with polystyrene (the minority component) homopolymers of different molecular weights. The preference for perpendicular orientation or hexagonal ordering of the nanocylinders over a large area in the asymmetric block copolymer can be controlled by adjusting the molecular weight of the blended homopolymer, and the perfection of hexagonal ordering of the perpendicular cylinders can be tuned by using a substrate whose surface tension is much different from that of the majority component of the block copolymer. Such highly controlled nanostructured block-copolymer materials, which have been obtained by a simple method independent of film thickness and interfacial tension between the blocks and the substrates, have wide-ranging commercial potential, e.g., for use in membranes and nanotemplates with size-tunable pores, bandgap-controlled photonic crystals, and other nanotechnological fields demanding a specific nanosize and nanomorphology.

The ablation behavior of amorphous [polystyrene (PS), polycarbonate (PC)] and crystalline [PET, glass-filled poly(butylene terephthalate) (PBT)] polymers by 248-nm KrF excimer laser irradiation were investigated for different injection-molding conditions, namely, injection flow rate, injection pressure, and mold temperature, as a possible method for evaluating processing effects in the specimens. For this purpose, dumbbell-shaped samples were injection-molded under different sets of processing conditions, and weight loss measurements were carried out for the different injection-molding conditions. Some of the crystalline (PET) samples were annealed at different annealing times and temperatures. For PET, the weight loss decreased with increasing mold temperature and remained insensitive to injection flow rate. Annealing time and temperature significantly reduced weight loss in PET. For PBT, the weight loss due to laser ablation decreased with increasing material packing due to pressure, and it also showed some sensitivity to flow rate variation. The major effect was seen with glass-filled PBT samples. The weight loss decreased drastically with increasing glass fiber content. Laser ablation allowed us to observe process-induced fiber orientation by scanning electron microscopy in PBT samples. For PS and PC, the weight loss increased with increasing injection flow rate and mold temperature and decreased with increasing injection pressure. The position near the gate showed higher ablation than the position at the end for all the conditions. A decrease in the material orientation with injection speed and mold temperature led to an increase in the weight loss, whereas an increase in the injection pressure, and consequently orientation, led to a lower weight loss for PS and PC. Higher residual stress samples showed higher weight losses. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 2006

Excimer laser irradiation provides a new and important method for polymer surface treatment. In this work, the weight loss of engineering polymers PC, ABS, PS, and nylon 6 were investigated following irradiation by KrF excimer laser. The experimental results revealed that the polymeric weight loss is nonlinearly related to the laser energy and laser frequency for most of the materials tested. The effects of laser irradiation on the thermal properties (T_g or T_m) of the polymers were investigated using DSC. It was found that the T_g and T_m of these materials decreased as a result of laser treatment, indicating the degradation effect of the laser irradiation procedure. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1024–1037, 2006

The objective of this work was to study the differences in the ultrasonic weld strength of polypropylene compounds with different fillers. The fillers were calcium carbonate, talc, mica, and glass fibers. The welder parameters were varied to determine the optimum set. These welder parameters were the weld time, weld force, trigger force, and amplitude. The results indicated that the weld time had the greatest effect on the weld strength of each of the filled compounds. Unfilled polypropylene had the highest weld strength under the optimum welding conditions, which were used as the baseline welding conditions. For each given filler, the weld strength was reduced as the filler loading increased. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1986–1998, 2004