共查询到19条相似文献,搜索用时 759 毫秒
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采用季戊四醇(PE)引发4-甲基-ε-己内酯(MeCL)单体开环聚合,得到一系列具有四臂拓扑结构的星型聚4-甲基-ε-己内酯(PMCL),再以丙烯酰氯对PMCL末端羟基进行双键化改性,得到端基双键化星型预聚物,该预聚物与光引发剂混合后可在紫外照射下交联成型。通过1 HNMR、GPC和旋转流变仪表征了PMCL预聚物的微观结构和流变性质。研究表明:成功制备了PMCL预聚物,聚合反应可控,且通过改变臂长可调节预聚物的流变特性。此外,随着预聚物臂长的增加,交联样品的模量下降但断裂伸长率有显著提高。 相似文献
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末端带有羟基的聚醚、聚酯预聚物是制备聚氨酯橡胶和塑料重要起始材料,而羟基终止的聚异戊二烯及聚丁二烯则可用以制备结构材料及火箭固体推进剂中的粘合剂。这些预聚物中羟基的含量是决定交联后形成网状结构聚合物性质的重要参数,需要建立准确测定的方法。最常用的测定方法是化学滴定法,但缺点是反应时间长,样品需要量大,预聚物不溶于水时用KOH滴定困难以及预聚物中如含有对碱敏感的基团不能应用。用IR测定预聚物中羟基,一般多用二硫化碳或四氯化碳为溶剂,使用厚的吸收池(如10厘米)测定3640cm~(-1)附近自由羟基的伸缩振动。但这种方法即使在羟基浓度很低时也 相似文献
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以1,4-丁二醇(BD)为引发剂, 辛酸亚锡为催化剂, 引发对二氧环己酮(PDO)开环聚合, 得到双端羟基型聚对二氧环己酮预聚物, 再以六亚甲基二异氰酸酯(HDI)为扩链剂制备高分子量的聚对二氧环己酮. 采用核磁共振谱对预聚物和扩链产物的结构进行了确认, 并详细考察了各种因素对扩链反应的影响. 研究结果表明, 加入适量的HDI, 于150 ℃反应60 min, 扩链效率在预聚物基础上可提高52倍, 而扩链产物的粘均分子量可达到25.7×104 g/mol. 相似文献
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聚氨酯已广泛用于泡沫塑料、涂料、油墨,绝缘材料和粘合剂等工业。其主要原料异氰酸酯单体具有毒性,从环境保护和提高产品质量角度要求聚氨酯预聚物中游离单体含量不超过1%。测定游离单体含量的方法有很多,其中气相色谱法由于汽化温度和柱温高,易使预聚物降解,结果偏高失真;ASTM法手续繁杂,适应性差。本工作建立了高效液相色谱法(HPLC)测定聚氨酯预聚物中游离甲苯二异氰酸酯(TDI)含量。并用以跟踪预聚物形成反应历程,控制产品 相似文献
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“活性”中间体PCL-PLA-OAl<用环氧乙烷扩链生成含聚醚羟端基的预聚物,它与Teyssie催化剂反应后取代其中的异丙氧基生成“活性”的预聚物催化体系,进而引发CL 聚合生成PCL-PLA-PCL ABA型嵌段共聚物,它的机械性能优于AB型共聚物,断裂伸长增大约一倍,具有微观相分离结构和可控制的生物降解性能及药物释放性能。本文亦提供了内酯与交酯嵌段共聚的新途径。 相似文献
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固相微萃取与气相色谱质谱联用快速监测水中的萘及硝基萘 总被引:13,自引:0,他引:13
采用涂有聚二甲基硅酮的纤维快速吸附水中的萘、1-硝基萘和2-硝基萘,再利用气相色谱的气化室温度热解析纤维上的待测物。方法简单、灵敏,不需要使用任何有机萃取溶剂。该种类型纤维可较好地吸附萘及硝基萘。加入硫酸钠可改善样品的基质,增加纤维吸附量。监测水中的萘、1-硝基萘和2-硝基萘的方法检出限可分别达0.25、0.30、0.20μg/L。 相似文献
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2 氨基 3 硝基吡啶和2 氨基 5 硝基吡啶的一级质谱图接近,单纯通过一级质谱图较难区分这两种异构体,利用离子阱质谱的串联质谱技术对2 氨基 3 硝基吡啶和2 氨基 5 硝基吡啶在离子阱内以He作碰撞气进行碰撞诱导裂解,所得的二级质谱图表明,两者之间存在明显的差别,可用于2 氨基 3 硝基吡啶和2 氨基 5 硝基吡啶的鉴别。 相似文献
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Grafted semi‐interpenetrating polymer networks (IPNs) were prepared from polyurethane (PU) prepolymers with polyester soft segments and hard segments containing carboxylic functional groups as well as polymethacrylate (PM) prepolymers with tertiary amine functional groups. The dependence of morphological and mechanical properties on the concentration of functional groups was studied. The enhanced miscibility of PU and PM prepolymers was observed at concentrations of functional groups of 0.25 mmol/g of polymer and above. Despite the improved miscibility, the PM prepolymers showed a tendency toward phase separation. Because the observed glass‐transition temperature shifts of PU prepolymers indicated substantial miscibility, we ascribed this phenomenon to the presence of methyl methacrylate rich sequences in the PM prepolymer. The observed changes in mechanical properties by increasing the content of functional groups were typical for ionomers. Young's modulus increased as a result of physical interactions between functional groups. A significant drop in tensile strength was observed in IPN samples with phase‐separated PU and PM prepolymers. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 115–123, 2002 相似文献
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环四硅氧烷乳液聚合制备弹性粒子及其反应动力学的研究 总被引:2,自引:0,他引:2
用八甲基环四硅氧烷(Me-D4)与四甲基四乙烯基环四硅氧烷(Vi-D4)乳液聚合得到了聚硅氧烷乳液,通过乙烯基的自由基聚合反应得到交联的乳胶粒子从而制备出有机硅弹性粒子.对乳液聚合的动力学和共聚物组成进行了研究,同时讨论了Me-D4和Vi-D4残基在聚合链上的分布 相似文献
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A study of the free-radical polymerization of isoprene and chloroprene leading to the preparation of telechelic prepolymers containing hydroxyl and carboxyl terminal groups has been carried out. The polymerization temperature was found to have a pronounced affect on the molecular weight distribution of the polyisoprenes, heterogeneity index values below 1.3 generally being found for prepolymers prepared at 60°C or below and index values higher than 1.3 being found for prepolymers prepared at higher temperatures. This change in heterogeneity index values with polymerization temperature was not observed with the polychloroprenes. 相似文献
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Eric J. Goethals 《Macromolecular Symposia》1992,59(1):217-231
An overview of newer or less-known synthetic methods for the synthesis of polymer networks containing ether, amine or sulfide functions or a combination of these functional groups with other functional groups, is presented. Emphasis is given on new methods starting from well - defined telechelic prepolymers. A number of these prepolymers are obtained by living cationic systems, more particularly cationic ring-opening and cationic vinyl ether polymerizations. 相似文献
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Phenyltrichlorosilane was hydrolyzed both ifi. toluene and in ether from which two kinds of prepolymers were obtained with different structures, molecular weights, and molecular weight distributions. Polymers were prepared from the prepolymers in various polymerization conditions. The ladderlike, branched, and crosslinked structures formed under different polymerization conditions were characterized by means of FTIR, ~1H and ~(29)Si-NMR, and elemental analysis. Azeotropic distillation of solvents and H_2O formed during polymerization was found useful in removing H_2O from the system and high molecular weight products with perfect ladderlike structure were obtained. 相似文献
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Samuel F. Reed 《Journal of polymer science. Part A, Polymer chemistry》1971,9(7):2029-2038
Telechelic prepolymers of butadiene, isoprene, and chloroprene with hydroxyl end- groups have been prepared by the solution polymerization of the dienes under free-radical initiation. 4,4′-Azobis(4-cyano-n-pentanol) was employed as the initiator. Liquid prepolymers were obtained with molecular weights of 2000 to 20,000 and with functionalities usually greater than 2. The preparative procedure and prepolymer characterization are described. 相似文献
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Samuel F. Reed 《Journal of polymer science. Part A, Polymer chemistry》1971,9(8):2147-2153
Butadiene, isoprene, and chloroprene have been polymerized in dioxane under free-radical initiation to give liquid prepolymers containing terminal carboxyl groups. 4,4′-Azobis(4-cyanovaleric acid) was employed as the initiator. The prepolymers were obtained with molecular weights of 12,000 to 2000 and with functionalities usually greater than 2.0. Experimental parameters were studied to determine their effect on prepolymer yields and properties. The general preparative procedure and prepolymer characterization are described. 相似文献