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【期刊论文】Influence of Microstructure on Space Charges of Polypropylene
杜强国, XIANG LI, , QIANGGUO DU, JIE KANG, DEMIN TU
Journal of Polymer Science: Part B: Polymer Physics, Vol. 40, 365-374 (2002),-0001,():
-1年11月30日
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.
charge transport, poly(, propylene), (, PP), , structure, morphology
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杜强国, Zhiang Li, Qiangguo Du*, Xuezhen Shi, Fenggang Tao, Quanrui Wang, Graham Swift, Shuguang Wu
Macromol. Rapid Commun. 21, 590-594 (2000),-0001,():
-1年11月30日
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.
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【期刊论文】Charge Distribution and Crystalline Structure in Polyethylene Nucleated with Sorbitol
杜强国, XIANG LI, , YI CAO, QIANGGUO DU, YI YIN, DEMIN TU
Journal of Applied Polymer Science, Vol. 82, 611-619 (2001),-0001,():
-1年11月30日
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.
charge distribution, polyethylene, Sorbitol, nonisothermal crystallization, SALS
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