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余鼎声, Hongde
Journal of Applied Polymer Science, Vol. 98, 146-152 (2005),-0001,():
-1年11月30日
Two
nanocomposites,
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余鼎声, JIAN
Journal of Macromolecular Science, Part B: Physics, 44: 303-315, 2005,-0001,():
-1年11月30日
The viscoelastic behavior of ethylene-propylene random copolymer with ultra-high molecular weight (UHPPR) and broad molecular weight distribution (MWD), produced with Ziegler-Natta catalyst, was investigated by means of oscillatory rheometry at 180℃, 200℃, and 220℃. The loss modulus (G") curves of 180℃ and 200℃ present a pronounced peak at 38.10 rad/s and 84.70 rad/s, respectively, while the peak of G00 curve at 220℃ locates beyond 100 rad/s. Compared with UHPPR, G"(v) curves at 180℃ and 200℃ for Ziegler-Natta catalyzed ethylenepropylene random copolymer (PPR) with conventional molecular weight and broad MWD, did not show a peak at 0.01–100 rad/s, respectively. This fact indicates that high molecular weight is responsible for a peak of G00 curves for UHPPR. On the other hand, the activation energy of crossover relaxation time tc (△Ha,c) andterminal relaxation time tm (△Ha,m) is 57.4 kJ/mol and 57.7 kJ/mol, respectively,and shows the same dependence of temperature, which also gives another evidenceof the presence of a peak in the G"(v) curves at 180℃ and 200℃. For UHPPR, the plateau modulus (G0N ) which was determined to be 4.51×105 Pa and 3.67×105 Pa at 180℃ and 200℃, respectively, decreases with increasing temperature and is independent of molecular weight and MWD. The entanglement points of each molecular chain for UHPPR are much higher than those for PPR with conventional molecular weight, which is a partial reason why the melt viscosity increases with increase of molecular weight.
ethylene-propylene
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余鼎声, DING
CHEM. RES. CHINESE U. 2005, 21(2), 227-231,-0001,():
-1年11月30日
The viscoelastic behavior of isotactic polypropylene with ultra-high molecular weight (UHPPH) and broad molecular weight distribution (MWD), produced in the presence of Ziegler-Natta catalyst, was investigated by means of oscillatory rheometry at 180 and 200℃, whose loss modulus (G") plots at 180 and 200℃ versus the natural logarithm of angular frequency (w) present a pronounced maximum at 34.35 and 69.21 rad/s, respectively, and do not show a maximum peak at 0.01-100rad/s for Ziegler-Natta catalyzing ethylenepropylene random copolymerization (PPR) with a conventional molecular weight and broad MWD. The fact indicates that the high molecular weight is responsible for a maximum peak of G" (w) us. Lnw curves for UHPPH. This makes it possible to determine the plateau modulus (G0N) of UHPPH from a certain experimental temperature G"(w) curve directly. For UHPPH, the G0N determined to be 4.28×105 and 3.62×105 Pa at 180 and 200℃, respectively, decreases with the increase of temperature and is independent of the molecular weight, which directly confirms reputation theoretical prediction that the G0N has no relation to the molecular weight.
Isotactic
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余鼎声, Dingsheng
D. Yu et al. Polymer 43 (2002) 3163-3168,-0001,():
-1年11月30日
Benzoxazine
Benzoxazine,
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