共查询到19条相似文献,搜索用时 203 毫秒
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利用核磁共振波谱仪、凝胶渗透色谱仪、X射线衍射仪、差示扫描量热仪、偏光显微镜及动态流变仪等研究了埋地排水管材专用聚丙烯(PP)树脂与给水管材专用PP树脂的结构与性能.结果表明:与给水管材专用 PP树脂相比,埋地排水管材专用PP树脂具有更高的相对分子质量、适宜的相对分子质量分布、合理的乙烯含量及不同的分子链序列结构.埋地排水管材专用PP树脂的弯曲模量大于1 600 MPa,简支梁缺口冲击强度大于80 kJ/m2,负荷变形温度大于100℃,具有优异的刚韧平衡性能和较高的熔体强度. 相似文献
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采用溶剂梯度分级结合凝胶渗透色谱(GPC)、核磁共振碳谱(13C-NMR)、差示扫描量热仪(DSC)等分析表征方法对利安德巴塞尔公司的高密度耐热聚乙烯管材树脂(PE-RT)4731B的分子链结构及聚集态结构进行了分析。结果表明,该PE-RT的结晶度为63 %,晶片厚度31 nm;相对分子质量呈双峰分布,相对分子质量分布达到18.0,低相对分子质量部分的重均相对分子质量(MW)为4.0×103~3.0×104,高相对分子质量部分的MW为3.0×105~6.0×105;短支链均匀分布于高分子链上,共聚单体含量高于1.25 %;高低相对分子质量组分配比为(50~55)∶(45~50)。 相似文献
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采用凝胶渗透色谱、核磁共振碳谱、差示扫描量热法等分析了牌号分别为4731B,SP980,DX800的进口管材专用耐热聚乙烯(PE-RT)的性能及分子结构、相对分子质量及其分布、共聚单体种类及含量、结晶性能等。结果表明:3个牌号的PE-RT均为中、高密度聚乙烯产品(密度为0.935~0.947 g/cm3),其中,4731B为乙烯与1-丁烯的共聚物,共聚单体含量低于SP980和DX800,相对分子质量分布较宽,结晶度为63%,晶片厚度为39.27 nm,晶粒尺寸较大,说明其具有较好的结晶性能。 相似文献
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采用差示扫描量热法分析、核磁共振碳谱、连续自成核退火热分级、高压毛细管流变、旋转流变等研究了国内外三种PE100级管材专用双峰(即相对分子质量分布呈双峰)聚乙烯(PE)的结构与性能。结果表明:三种双峰PE片晶厚度分布指数接近,易形成较厚片晶;属于假塑性流体,剪切黏度对剪切速率变化敏感;熔体强度高,抗熔垂性能好,适宜高速挤出成型,制作大口径、尺寸稳定性产品。PE100级管材专用树脂P6006熔体强度和零剪切黏度较高,推断P6006相对分子质量高,且高相对分子质量部分含量高;3490LS剪切黏度对剪切速率变化最敏感,剪切变稀明显;3490LS相对分子质量分布较宽,具有较好的加工性能。 相似文献
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分析了高密度聚乙烯(HDPE)管材专用树脂DGDB 2480H及典型双峰PE 100级管材专用树脂的性能。两者的力学性能相当;DGDB 2480H具有较低的剪切黏度,有利于管材的加工成型,熔体强度为1.05 MPa,与国产及进口管材专用树脂相当,比普通HDPE大,有利于大口径管材的挤出。 相似文献
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采用溶液聚合的方法制备了系列相对分子质量(简称分子量,下同)不同的苯乙烯-alt-马来酸酐共聚物(SMA),并通过FTIR、1HNMR、13CNMR对产物结构进行了表征,通过DSC对其热性能进行了分析。考察了分子量大小对其在皮革中复鞣填充作用的影响。结果表明,分子量是影响SMA复鞣填充作用的重要因素,随聚合物分子量的增加,处理革的抗张强度降低、撕裂强度增加、部位差降低率增大。当SMA的Mn为6 620时,处理革的撕裂强度、抗张强度和部位差降低率分别为18.325 N/mm、9.519 N/mm2和7.44%,当SMA的Mn为59 058时,处理革的撕裂强度、抗张强度和部位差率降低率分别为20.577 N/mm、5.539 N/mm2和44.98%。 相似文献
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The aim of this work was to model the mechanical properties of different blends of polyisobutylene (PIB) pressure sensitive adhesives (PSAs) with different molecular weights (36,000, 51,000, 75,000, 400,000, and 1,100,000). The mechanical properties of PSAs are usually described by tack, peel, and shear strength which are strongly depended on the bulk viscoelastic properties of the adhesive system. It is assumed that the blends of high and low molecular weight PIB could affect these properties. According to D-optimal design of Design Expert software, various blends of five different molecular weights of PIB have been selected for study in this investigation. Using manual regression analysis, the quadratic model generated for three responses (tack, peel, and shear) was found to be statistically significant (p < 0.05). It was found that tack increases with decreasing molecular weight. It was also found that the presence of B10 and B12 as low molecular weight polymers and B50 as a high molecular weight polymer in increasing peel strength was more dominant compared with B15 and B100. Furthermore, shear strength was found to increase with an increasing concentration of the low molecular weight PIB, B15. The results have shown that statistical analysis meets theoretical expectations and they suggest desired blends of polymer for different aims. 相似文献
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Mark L. Crowder Amod A. Ogale Eugene R. Moore Brian D. Dalke 《Polymer Engineering and Science》1994,34(19):1497-1505
This study investigated the interrelationship between strength and flow characteristics of general-purpose polystyrene (GPPS) used in injection molding applications. The ease of flow was chosen as a measure of processability and was evaluated using the melt flow rate and capillary rheometer techniques. Of the different strength tests that were examined, flexural and notched tensile strength tests were most effective in differentiating between commercial grades of high and low molecular weight GPPS. While characterizing strength of injection molded specimens, the degree of molecular orientation was taken into consideration. For unplasticized resins, increasing the weight average molecular weight by about 100,000 enhanced the flexural strength by 10%, but also increased the viscosity at low shear rates (10 to 100 s?1). The increase in molecular weight had virtually no effect on viscosity at the highest shear rates (up to 10,000 s?1). Plasticized resins displayed a 6% loss in flexural strength as well as a significant reduction in viscosity (throughout the shear rate range) as compared with the unplasticized resins. As expected, the improvement in strength achieved by increasing molecular weight leads to a simultaneous increase in the viscosity, i.e., a deterioration of processability. In addition, our study indicates that for samples without preferential molecular orientation, narrowing the molecular weight distribution significantly improves the balance of strength and melt flow rate properties. 相似文献
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The gel effect will bring a violent increase of conversion for methyl methacrylate (MMA) polymerization in a short time. It will be very dangerous for the reactor, as it causes an increase of molecular weight and broadens the molecular weight distribution. To unify the kinetics, molecular weight, and its distribution, on the basis of the mathematical models for semibatch polymerization of MMA, three controlled objectives that are the heat load distribution index, the change in molecular weight, and molecular weight distribution index are presented. Three materials (monomer, solvent, and chain transfer agent) and their flow rate and feeding mode are analyzed for the open control of kinetics, molecular weight, and its distribution. The optimum flow rate and mode are obtained. The heat load distribution index and molecular weight distribution index are even less than 2.0 and 2.2, respectively. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4399–4405, 2006 相似文献
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Von Alfred Hauss 《大分子材料与工程》1969,8(1):73-86
Mechanical properties and melt flow behaviour have been measured on thermal polystyrenes in order to study the effect of different molecular weight and different molecular weight distribution. The mechanical properties (impact strength, tensile strength and flexural strength) were found to depend upon a critical molecular weight Mw = 1.5 × 105, where the polystyrenes reached ultimate strength. An influence of molecular weight distribution only can be observed when the average molecular weight is near the critical molecular weight limit. The broader the distribution, the poorer are mechanical properties. Injection molded specimens with different molecular weight distribution but equal average molecular weight showed different molecular orientation and different anisotropic mechanical properties. On the basis of equal orientation the narrow distributed specimens showed higher mechanical strength in direction of orientation. The broader the distribution, the higher the elastic properties of melt. An optimum of physical properties and ease of fabrication will be obtained with narrow molecular weight distributed polystyrenes with an average molecular weight slightly above the critical molecular weight limit. 相似文献
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采用不同分子量的端羟基聚丁二烯(HTPB)和甲苯二异氰酸酯为主要原料合成预聚物,以N,N-M(2-羟丙基)苯胺为扩链剂制备了浇注型聚氨酯弹性体,并着重研究了预聚体中游离异氰酸酯基含量、扩链剂用量、HTPB分子量以及不同分子量HTPB并用和扩链剂并用对弹性体力学性能的影响,还对弹性体的结构与形态进行了初步分析和探讨。结果表明,预聚体中游离异氰酸酯基含量为9.0%时,拉伸强度最大,且综合性能最佳;扩链系数为0.89时,拉伸强度、定伸应力、硬度出现最大值;HTPB分子量增大,弹性体力学性能有下降趋势,不同分子量HTPB并用时分子量大的HTPB增多,力学性能下降;当HTPBMn=3100,游离异氰酸酯基含量为9.0%,扩链系数为0.89时,弹性体综合性能最佳。电子显微镜照片显示HTPB型聚氨酯有微相分离,且软硬键段分布不规整。 相似文献
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以氢化丙烯酸松香为增黏树脂,将其溶解在丙烯酸酯单体中,预乳化后采用半连续乳液聚合工艺制备了氢化丙烯酸松香/丙烯酸酯复合乳液。研究了氢化丙烯酸松香的用量对单体转化率、凝胶率、溶胶相对分子质量及其分布、乳胶膜的玻璃化温度(Tg)和压敏胶粘接性能等的影响。结果表明,氢化丙烯酸松香对单体聚合具有一定的阻聚作用,随着氢化丙烯酸松香用量的增加,单体转化率、凝胶率及相对分子质量下降,相对分子质量分布变窄。氢化丙烯酸松香的合适用量为8.0%wt,此时压敏胶的初黏力为15#,180°剥离强度为10.6N.25mm-1,持黏力大于120h。 相似文献