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51.
本文用纤维素材料经酸分解制备具有平衡聚合度(LODP)的微晶纤维素,再分散成超细纤维素胶体(准均相纤维素体系)。用扫描电镜(SEM)观察处理前后的纤维素颗粒尺寸,并比较它们和丙烯酰胺接枝共聚的反应速率、聚合转化率、接枝率、接技效率、聚丙烯酰胺支链的分子量及其分布的情况。 相似文献
52.
53.
气相法聚乙烯高效催化剂的进展 总被引:2,自引:0,他引:2
综述了国内外气相法聚乙烯高效催化剂研究进展概况,以及各种新型高效催化剂制备技术和性能,并对开发我国新型高效推化剂提出了看法。 相似文献
54.
Polystyrene (PS)/poly(ethylene oxide) (PEO) prototype brushes were prepared by alternating free‐radical copolymerization of methacryloyl‐terminated PS and α‐vinylbenzyl‐ω‐hydroxy or α‐vinylbenzyl‐ω‐perfluoroalkyl (Rf) PEO macromonomers with the addition of Lewis acid (SnCl4). It was found from their dilute‐solution properties that PS/PEO end‐capped with Rf (PBRf), and PS/PEO having OH groups at terminal ends (PBOH) prototype brushes formed a single molecule in benzene and aggregates in chloroform, respectively. However, the brush PBOH formed a single molecule in N,N‐dimethylformamide. Such aggregation behaviors seemed to be caused by the interaction between hydroxy groups of PEO chain ends. The brush PBOH was also converted into PBRf‐type brush by chemical modification, using corresponding acid chloride. The substitution of Rf groups was ~70% due to slipping of terminal hydroxy groups into PEO internal domains. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 772–778, 2006 相似文献
55.
乙酸乙烯酯(VAc)与丙烯酸(AA)在GeCl_4及BCl_3存在下通过自由基聚合可得到交替共聚物。对GeCl_4体系,聚合反应速率正比于[引发剂]~(0.5)。当VAc/AA=1:1(mol比)时有最大反应速率。CCl_4对本聚合反应无链转移作用。通过紫外光谱分析可证实VAc及AA均与GeC\(?)生成络合物;ESR分析表明,络合AA自由基较未络合AA有较强的阳离子特性,交替共聚的原因可能与络合AA自由基及活化单体络合物二者有关。 相似文献
56.
The formation of a series of semiinterpenetrating network (SIPN) hydrogels made by free‐radical copolymerization of N‐isopropylacrylamide (NIPA) and 2‐acrylamido‐2‐methylpropanesulphonic acid (AMPS) with varying comonomer mole ratios, crosslinked with N,N′‐methylene‐bisacrylamide (MBAA) in the presence of poly(ethylene glycol) (PEG) with average molecular weight 6,000 g mol?1 was studied via determination of complex viscosity, η*, using plate–plate rheometry. The isothermal time dependence of η* at various temperatures or the variation of η* with temperature of pregel solutions was utilized to detect the onset of gelation. The SIPN systems were compared with the corresponding gels made under the same conditions in the absence of PEG. The copolymer mainchain composition has a major effect on the time or temperature for onset of gelation and in particular gelation appears to be inhibited to some extent by MBAA when the AMPS/NIPA mole ratio in the pregel solution exceeds 0.5. The presence or absence of PEG in pregel solutions has a lesser effect on gelation. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2083–2087, 2004 相似文献
57.
On Cu-ZSM-5 zeolite at room temperature, propane is physisorbed, while propene shows characteristics of chemisorption. The chemisorption mode has certain advantages for the catalytic control of automotive emissions. Alkane and alkene adsorption equilibria and kinetics are compared on Cu-ZSM-5 and on ZSM-5 free of alumina. The results are discussed in terms of the Langmuir adsorption isotherm. 相似文献
58.
The curing kinetics of bismaleimide modified with diallylbisphenol A were investigated for different ratios of 1,1′‐(methylene di‐4,1‐phenylene) bismaleimide and diallylbisphenol A with differential scanning calorimetry. Multiheating‐rate and isothermal methods were used to study the kinetics of the curing process. The results indicated that the activation energy changed with the extent of conversion. The activation energy obtained by the multiheating‐rate method was higher than that obtained by the isothermal method. Two kinetic models (autocatalytic and nth‐order) were successfully used to model the curing process. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2229–2240, 2003 相似文献
59.
Thermal radical copolymerization of styrene (S) and maleimide (MI) at 125°C in diglyme in the presence of 2,2,6,6‐tetramethylpiperidin‐1‐yloxyl radical (TEMPO) was studied. Mole fractions of maleimide in the feed, FMI, varied in the range 0.1–0.9. A quasiliving reaction process proceeded yielding copolymers with a low polydispersity (Mw/Mn = 1.17–1.41). The found azeotropic composition, (FMI)A = 0.46, did not differ substantially from that (0.5) in the conventional radical S‐MI copolymerization. At a higher conversion or MI content in the feed, deactivation of the copolymer chains occurred. The obtained TEMPO‐terminated S‐MI copolymers readily initiated polymerization of styrene; chain extension of the macroinitiators took place, giving poly(S‐co‐MI)‐block‐poly(S) diblock copolymers. The synthesized copolymers containing S and MI units were characterized by elemental analysis, NMR spectroscopy, size‐exclusion chromatography, and differential scanning calorimetry. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1863–1868, 2004 相似文献
60.
对前文 (I)的共聚动力学模型进行了分析与简化 ,并分别通过对各影响因素的单因素实验和多因素相互作用实验对模型进行了进一步的考核 ,确定了模型参数并通过模型对聚合动力学行为作了说明 相似文献