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141.
The effect of end groups (2NH2) of poly(ethylene glycol) (PEG) on the miscibility and crystallization behaviors of binary crystalline blends of PEG/poly(L ‐lactic acid) (PLLA) were investigated. The results of conductivity meter and dielectric analyzer (DEA) implied the existence of ions, which could be explained by the amine groups of PEG gaining the protons from the carboxylic acid groups of PLLA. The miscibility of PEG(2NH2)/PLLA blends was the best because of the ionic interaction as compared with PEG(2OH, 1OH‐1CH3, and 2CH3)/PLLA blends. Since the ionic interaction formed only at the chain ends of PEG(2NH2) and PLLA, unlike hydrogen bonds forming at various sites along the chains in the other PEG/PLLA blend systems, the folding of PLLA blended with PEG(2NH2) was affected in a different manner. Thus the fold surface free energy played an important role on the crystallization rate of PLLA for the PEG(2NH2)/PLLA blend system. PLLA had the least fold surface free energy and the fast crystallization rate in the PEG(2NH2)/PLLA blend system, among all the PEG/PLLA systems studied. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
142.
Han‐Lang Wu Chen‐Chi M. Ma Chun‐Chieh Lin Yie‐Chan Chiu Chih‐Yuan Chen Chin‐Lung Chiang 《应用聚合物科学杂志》2008,107(5):3236-3243
Poly(arylene ether benzonitrile) (PAEBN) was synthesized with 2,6‐dichlorobenzonitrile and biphenol. PAEBNs with various molecular weights (MWs), 1,640,000 and 185,000 g/mol, were synthesized by control of the stoichiometry of the monomers and were blended with sulfonated poly(ether ether ketone) (SPEEK). The effects of MW on the water uptake, swelling, methanol permeability, and proton conductivity of the SPEEK/PAEBN blend membranes were investigated. The molecular mobility of the SPEEK/PAEBN blends was also examined in this study. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
143.
根据具体工程实例,介绍了在基坑开挖时采用土钉加锚杆的联合支护方式后在施工过程中出现坍塌裂缝的现象,针对这一现象,分析了施工条件与环境,得出了事故发生的原因,并结合实际情况提出了处理措施. 相似文献
144.
基于带传动在稳定工作时的受力平衡,从理论上导出了摆架式自动张紧装置所产生的张紧力的计算公式。结果表明:只要合理选择计算安装参数,其张紧力总能满足张紧条件的要求,以对张紧装置进行设计计算;并指出该装置产生的张紧力,具有随外载荷变化而自动调节的性能,使传力零件部分卸载。 相似文献
145.
Solution-chemistry analysis of ammonium bicarbonate consumption in rare-earth-element precipitation 总被引:2,自引:0,他引:2
R. Chi Z. Zhou Z. Xu Y. Hu G. Zhu S. Xu 《Metallurgical and Materials Transactions B》2003,34(5):611-617
A solution-chemistry analysis is applied to estimating the consumption of ammonium bicarbonate in the recovery of rare-earth
(RE) elements from leachates of weathered clays. The theoretical analysis shows that a two-step process is needed for recovering
RE from the leachates of the weathered clays by precipitation using ammonium bicarbonate. The first step is a precipitation
at solution pH 5 to remove impurities such as Fe and Al. The second step is to precipitate RE by adjusting the solution pH
above 8. The consumption of ammonium bicarbonate was found to depend on the concentration of RE elements and impurities in
the leachates. The total amount of ammonium bicarbonate consumption for the entire process was determined experimentally,
and the results showed an excellent agreement with that calculated based on solution-chemistry analysis. The decomposition
of H2CO3 was identified as one of the main causes of ammonium bicarbonate overdose, accounting for up to 41 pct in comparison to 20
pct consumption for the removal of impurities. The amount of ammonium bicarbonate required in terms of the NH4HCO3: RE2O3 (RE oxides) molar ratio was found to be 4:1 for maximal RE recovery. An overall RE recovery around 90 pct was achieved with
a product purity being about 90 pct. 相似文献
146.
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149.
曲柄摇杆机构的三圆图解设计法 总被引:1,自引:0,他引:1
这里探讨了对给定行程速比系数K,摇杆摆角ψ,另外再给定摇杆长度l3(机架长度l4)、曲柄长度l1(连杆长度l2)等,找出如何运用辅助圆图解设计曲柄摇杆机构的方法。 相似文献
150.