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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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【期刊论文】The phase diagrams of mixtures of EVAL and PEG in relation to membrane formation
杜强国, Bo Liu, Qiangguo Du, Yuliang Yang*
Journal of Membrane Science 180(2000)81-92,-0001,():
-1年11月30日
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*.
Phase diagram, E, V, A, L, , PEG, TIPS, Interaction parameter
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杜强国, Liang Shen, Yijian Lin, Qiangguo Du*, Wei Zhong, Yuliang Yang
Polymer 46(2005)5758-5766,-0001,():
-1年11月30日
The polyamide-6/attapulgite nanocomposites were prepared via an in situ polymerization route with attapulgites pre-modified with cetyltrimethylammonium bromide (CTAB) and toluene-2,4-diisocyanate (TDI). Morphology observation showed that the exfoliated attapulgite fibers were well dispersed in the polyamide-6 matrix on a nanometer scale and formed a percolation network structure. The rheological behaviors of such polymer/fibrous clay nanocompostie samples were investigated by an ARES rheometer with parallel plate geometry. The storage moduli (G0), loss moduli (G00), and dynamic viscosities of these samples increased monotonically with attapulgite content at low frequencies. The presence of attapulgites caused these nanocomposite melts to have solid-like behaviors and slower relaxation. This behavior can be explained in terms of the development of a grafting-percolated fibrous-silicate network structure. Monte Carlo simulations were performed to determine the critical threshold for attapulgites fibers in 3D. The calculated critical threshold from simulations fitted the results of our rheological experiments very well.
Polyamide/, silicate nanocomposite, Rheology, Percolation
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杜强国, Haitao Wang, Peng Xu, Wei Zhong*, Liang Shen, Qiangguo Du*
Polymer Degradation and Stability 87(2005)319-327,-0001,():
-1年11月30日
Nanocomposites from poly(methyl methacrylate) (PMMA), silica (SiO2) and zirconia (ZrO2) were prepared using a novel nonhydrolytic sol-gel process. Silicic acid and zirconium oxychloride (ZrOCl2 8H2O) were used as the precursors of SiO2 and ZrO2, respectively. FT-IR and SEM results showed that nanometre-scaled SiO2/ZrO2 particles were uniformly distributed in and covalently bonded to the PMMA host matrix without macroscopic organiceinorganic phase separation, which was also confirmed by solvent extraction experiments. It was found that the transmittance of the nanocomposite films in the visible region remained above 95% even at 20wt% inorganic content and increased proportionally with decreasing inorganic content. The thermal stability and the thermal decomposition kinetics of the composites were studied. The results indicated that the activation energy (Ea) of the thermal decomposition of PMMA main chains in the composites was increased due to the addition of inorganic moieties. This kind of composite material may have the potential for applications in optical devices.
PMMA, Silica, Zirconia, Nanocomposites, Organiceinorganic
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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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