A novel process to prepare microporous hollow fiber membranes is proposed. Fibers of blends of isotactic polypropylene (i-PP) and atactic polypropylene (a-PP) spun under high take-up draw ratio are found to be elastic. Small angle X-ray scattering (SAXS) observation indicates that fibers have row-nucleated lamella structure normal to the fiber direction. Microporous polypropylene hollow fiber membranes were obtained from the fibers by extraction of atactic polypropylene and cool-stretching. The membranes have smaller pore size and higher permeability than those of traditional stretch method. The mechanism of micropore formation is discussed.

The phase diagrams of various ethylene-vinyl alcohol (EVAL) copolymer with different hydroxyl (OH) group contents and poly(ethylene glycol) (PEG) with different molecular weights (ranging from 200 to 600) are determined. It is found experimentally that both the liquid-liquid (L-L) phase boundaries and the crystallization curves are shifted to higher temperature when the OH group contents in EVAL increase. On the other hand, only the L-L phase boundaries shift to higher temperature when the molecular weights of PEG increase. These phenomena are interpreted by using solubility parameters (δd, δp) to estimate the Flory-Huggins interaction parameters, χ*, of the mixtures. By extrapolating the L-L bi-phasic curves from cloud points of temperature (Tcloud), the experimental interaction parameters χ* are obtained, which are linearly correlated to the theoretically estimated interaction parameters, χ*.

A peroxide monomer, 4,49-divinyl benzoyl peroxide (DVBPO), was synthesized. Bulk copolymerization of DVBPO with methyl methacrylate (MMA) was initiated by di(2-ethyl hexyl)peroxy carbonate (EHP). DSC curves and the appearance of crosslinking of the product showed that DVBPO can copolymerize with MMA. The grafting copolymerization of butyl acrylate (BA) onto the copolymer was performed. The grafting efficiency (GE), determined by Soxhlet extraction, was high.

The charge distribution in samples under direct current electrical field was measured by the pulsed electro-acoustic method, which showed that the space charges were greatly decreased and field distribution tended to be uniform in low-density polyethylene (LDPE) by adding 0.3 wt% bis-(p-ethylbenzylidene)sorbitol. The crystalline structures of LDPE and LDPE/sorbitol were studied. The non-isothermal crystallization kinetics were investigated by differential scanning calorimetry, which showed that sorbitol increases crystallization temperature and crystallinity, but lowers the Avrami exponent of crystallization. The results of wide-angle X-ray diffraction (WAXD) and small-angle light scattering (SALS) experiments show that the crystal form does not change, whereas the perfection of spherulites degrades in the presence of sorbitol. In addition to the obvious difference in crystalline morphology, observed by scanning electron microscopy, the spherulites in the LDPE/sorbitol sample are smaller in size and more in number than those of LDPE. It is well known that in semicrystalline polymers, impurities are expelled from crystalline regions into amorphous regions or interfaces of spherulites. The decrease of space charges can probably be attributed to the uniform distribution of impurities in the whole material, with smaller and imperfect spherulites.

The correlation of chemical structure, crystalline morphology, and space charge distribution under a dc electrical field was investigated with three kinds of poly(propylene) (PP) with a different chemical structure, that is, homogeneous PP and block copolymer and random copolymer of PP. The space charge distribution of the samples was prominently affected by their chemical sequence structure and crystalline microstructure. Among samples of different PPs, all isothermally crystallized at 140℃, the sample of random coPP represents the most well proportional space charge distribution and the smallest number of space charges. The effect of thermal history on the space charge distribution was also investigated by the samples of block coPP. The sample thermally treated at 50℃ clearly represents a better proportional distribution than that at higher temperature of 140 and 100℃. Subsequent experiments indicate that the better proportional distribution attributes to imperfect and fine sperulites with the fine distribution of the "amorphous" region. The imperfect and fine sperulites originate from the random incorporation of ethylene segments or units into PP chains or fromthe low annealing temperature, and play an important role in the formation of shallowtraps and transportation of space charges.