分子结构对双峰管材专用树脂流变性能的影响

对3种双峰聚乙烯管材专用树脂进行了结构性能及毛细管流变行为、拉伸流变行为的研究。结果表明:双峰管材专用树脂熔体流动速率低(0.23～0.25 g/10 min),结晶性能好(熔点128℃以上,结晶温度115℃以上,结晶度大于65%),相对分子质量分布宽。不同管材专用树脂的结构差异决定了其流变加工性能。少量低相对分子质量尾端组分对挤出流变行为的影响显著,可以降低低剪切速率下的黏度和压力。提高高相对分子质量组分所占比例,比增大高相对分子质量组分的相对分子质量大小对提高熔体强度的效果更明显。     

LDPE棚膜专用树脂的加工性能

研究了低密度聚乙烯棚膜专用树脂LD165的基础物性和流变性能。结果表明．LD165具有相对分子质量高、相对分子质量分布窄、总支化度低的分子结构特点,同时其结晶度及结晶速率高．还具有较高的熔体张力和牵仲速率,成膜稳定性能好。LD165扭矩略高、加工能耗高,不过,其与线型低密度聚乙烯的共混物的扭矩值与对比试样相当。适当提高加工温度、吹胀比,有利于提高LD165薄膜的光学性能和力学纵横向平衡性能。     

PE树脂的流变行为与其结构性能的关系

综述了聚乙烯(PE)树脂的流变行为与其相对分子质量、相对分子质量分布、支化结构、加工性能、制品性能的关系,介绍了用流变手段及参数表征PE树脂分子结构的方法.建议加大PE树脂流变行为的研究力度,为PE树脂的产品开发与推广应用提供技术支持.     

耐热聚乙烯管材专用树脂的结构与性能

研究了3种耐热聚乙烯管材专用树脂的结构与性能。它们的共同特征为熔体流动速率低于0.7 g/10 min,密度为0.930~0.944 g/cm3,相对分子质量为(1.5~2.5)×105,可以为窄相对分子质量分布,也可以为中等相对分子质量分布。1-己烯共聚产品与1-辛烯共聚产品性质较为接近,都是窄相对分子质量分布,而1-丁烯共聚产品具有相对分子质量高(2.0×105以上),相对分子质量分布中等(10左右),熔体流动速率低(低于0.3 g/10min)、密度高(大于0.940 g/cm3)、拉伸屈服强度高、弯曲模量高、熔融峰温高、结晶峰温高的特点。相同条件下,1-丁烯共聚产品具有较高的黏度和模量。     

最新专利文摘

聚乙烯管材树脂1种聚乙烯管材树脂由质量分数44%～55%高相对分子质量聚乙烯和45%～56%低相对分子质量聚乙烯组成。高相对分子质量聚乙烯为密度0.913～0.923 g/cm~3线型低密度聚乙烯,熔体流动速率0.02～0.20 g/10 min(190℃,21.6 kg下);组成低相对分子质量聚乙烯的高密度聚乙烯密度至少为0.969 g/cm~3,且其熔体流动速率大于100 g/10 min;其中树脂密度(D)和低相对分子质量聚乙烯质量分数(P1)之间关系定义为(0.055P1+0.916)相似文献   

茂金属线形低密度聚乙烯树脂结构性能分析

分析了4种薄膜用线形低密度茂金属聚乙烯(PE-mLLD)及独山子石化生产的线形低密度聚乙烯(PE-LLD)的基本物性指标、热力学性能、凝聚态结构、相对分子质量及其分布、分子链结构及流变性能。结果表明,Exxon Mobile公司的3个PE-mLLD样品均采用己烯共聚,样品具有两种结构,相对分子质量分布较窄的PE-mLLD分子链规整性较好,加工性能较差,但力学性能优于PE-LLD;相对分子质量分布宽的PE-mLLD分子链结构中支化点较多,加工性能较好;DOW公司的样品采用辛烯作为共聚单体,相对分子质量分布较宽,加工性能及力学性能综合表现较好。     

双峰PE100级管材专用树脂的结构与性能北大核心

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。     

高密度聚乙烯流变结晶性能对发泡的影响研究

采用差示扫描量热仪（DSC）和Hakke平板旋转流变仪测试了2种不同高密度聚乙烯（PE-HD）的热性能和动态流变性能,结合间歇发泡实验探究了PE-HD的发泡性能。结果表明,PE-HD的结晶速率以及黏弹特性对其发泡性能有明显地影响;HDPE6098具有适合发泡的流变特性和相对分子质量分布以及较快的结晶速率,可以获得发泡倍率为17.69倍,泡孔密度为1.30×10^6个/cm3的样品;而HDPE7000F由于高相对分子质量区域较大,模量较大,导致发泡过程中泡孔生长受到限制,获得的制品较差。     

瓶盖专用HDPE FHP5050的开发及性能评价

通过工艺参数的调整,采用低压淤浆法工艺开发了瓶盖专用高密度聚乙烯(HDPE)FHP5050,并研究了其性能。结果表明：FHP5050的拉伸屈服应力、断裂拉伸应变等均达到标准要求,相对分子质量分布与进口HDPE差异不大,高相对分子质量部分含量也较为接近,结晶性能、流变性能与进口HDPE一致。另外,FHP5050的气味测试、卫生性能检测也符合要求。     

中型中空容器吹塑专用HDPE的结构与性能

从共聚单体含量、相对分子质量、力学性能、熔融结晶性能、流变性能等分析了国产与进口中型中空容器吹塑专用高密度聚乙烯(HDPE)的性能差异。结果表明:HDPE HXM50100N的重均分子量更高,相对分子质量分布较宽,刚性突出,弯曲模量达到1 430 MPa,且熔体强度高。     

一种高密度PE-RTⅡ型管材树脂分子链结构剖析

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)。     

Anomalous rheological properties of polyethylene molecular composites

The effect of molecular weight on the rheological properties in the molten state has been studied for binary blends of high‐density polyethylene obtained by the Zieglar–Natta catalyst and low‐density polyethylene produced in an autoclave process. The blends composed of high‐density polyethylene with a high molecular weight and low‐density polyethylene show a higher drawdown force than the individual pure components, whereas the blends of high‐density polyethylene with a low molecular weight and low‐density polyethylene do not exhibit anomalous behavior. The pronounced drawdown force for the former blend system is attributed to the viscous enhancement in the linear viscoelastic region as well as the nonlinear strain‐hardening behavior in the elongational viscosity. POLYM. ENG. SCI. 46:1284–1291, 2006. © 2006 Society of Plastics Engineers     

PBS结晶影响因素的研究

采用偏光显微镜对聚丁二酸丁二醇酯(PBS)的结晶影响因素进行了研究。结果表明:在等温结晶时,PBS的最佳结晶温度随着分子量的增大而提高,当分子量增到一定值后,最佳结晶温度受分子量的影响很小。结晶温度一定时,PBS的晶体尺寸随着结晶时间的延长而增大。结晶时间一定时,PBS的晶体尺寸随着结晶温度的提高而先增大后减小。数均分子量为1×103、8×103、6×104、1×105的PBS最佳结晶温度分别为40℃~50℃、80℃、80℃、90℃。低分子量的PBS在较短的结晶时间内晶体尺寸就已较大,而高分子量的PBS在较长的时间内才能形成较大尺寸的晶体,数均分子量为8×103、6×104、1×105的PBS在最佳结晶温度形成较好结晶的时间分别为10min、20min、25min。     

Influence of high molecular weight component on the hierarchical crystalline structures of injection‐molded bars of polyethylene

A small amount of high molecular weight molecules can have a dramatic influence on the flow‐induced crystallization kinetics and orientation of polymers. To elucidate the effects of the high molecular weight component under a real processing process, we prepared model blends in which high density polyethylene with a high molecular weight and wide molecular weight distribution was blended with a metallocene polyethylene with a low molecular weight and very narrow molecular weight distribution. To enhance the shear strength, gas‐assisted injection molding was utilized in producing the molded bars. The hierarchical structures and orientation behavior of the molded bars were intensively explored by using scanning electron microscopy and two‐dimensional wide‐angle X‐ray diffraction, focusing on effects of the high molecular weight component on the formation of the shish kebab structure. It was found that there exists a critical concentration of high molecular weight component for the formation of a shish kebab structure. The threshold was about 5.5–7.0 times larger than the chain overlap concentration, suggesting an important role of entanglements of the high molecular weight component. Moreover, the rheological properties of molten polyethylene melts were studied by dynamic rheological measurements and a critical characteristic relaxation time for shish kebab formation was obtained under the processing conditions adopted in this research. © 2013 Society of Chemical Industry     

Competition between chain scission and branching formation in the processing of high‐density polyethylene: Effect of processing parameters and of stabilizers

Two samples of high‐density polyethylene with different molecular weight were processed in a batch mixer and the rheological and structural properties were investigated. In particular, the effect of different processing parameters and the eventual presence of different stabilizers were evaluated. Actually, two reactions may occur during processing: branching/crosslinking or chain scission. The results indicate that when the processing conditions promote a scarce mobility of the macromolecular chains (lower temperatures, lower mixing speed, and higher molecular weight), branching is more favored than chain scission. On increasing the mobility of the chain (higher temperature, higher mixing speed, and lower initial molecular weight), branching appears still the predominant reaction, but the chain scission becomes progressively more important. In both cases, no crosslinking occurs. The presence of stabilizers has different effects on the relative extent of branching or chain scission reactions depending on the kind and of the amount of stabilizer and on the processing condition adopted. The correct choice of a stabilizer system will, therefore, depend on the desired final structure. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

凝胶纺丝法制备超高分子量聚乙烯/高分子量聚乙烯纤维延伸性能的研究

用凝胶纺丝法制备了超高分子量聚乙烯(UHMWPE)/高分子量聚乙烯(HDPE)纤维,探讨了添加不同种类高分子量聚乙烯对凝胶初生纤维在后续延伸过程中延伸性能的影响。结果表明在固定制备条件时,当超高分子量聚乙烯(UHMWPE)/高分子量聚乙烯(HDPE)的质量比在最适当质量比时,高分子量聚乙烯的分子量为1.5～2.0×104时,所制备的凝胶初生纤维的可延伸比达最大值。     

高聚合度PVC S—1700树脂的特性及性能

本文采用凝胶渗透色谱仪，差示扫描热量仪研究了高聚合度ＰＶＣ Ｓ－１７００树脂的分子量及分布，玻璃化转化温度，并对该树脂的加工行为进行了考察。试验结果表明，加低聚合度ＰＶＣ树脂相比，ＰＶＣ Ｓ－１７００树脂的分子量增大，分布变宽，Ｔｇ升高，从而导致材料的加工温度升高，力学性能提高。由材料的热老化试验表明，ＰＶＣ Ｓ－１７００还具有良好的耐老化性能。     

聚烯烃弹性体的结构与熔体黏度关系的研究

采用凝胶渗透色谱仪和核磁共振仪表征了一系列聚烯烃弹性体（POE）样品的结构,并用毛细管流变仪考察了其挤出稳定性、剪切依赖性和黏温依赖性,分析了熔体黏度与聚合物结构的关系。结果表明,随着剪切速率的提高,高相对分子质量的POE熔体易出现不稳定流动,挤出物表面发生畸变;相对分子质量越大、温度越低、共聚单体含越高,发生不稳定流动的临界剪切速率c越低;POE的剪切黏度很大程度上受相对分子质量的影响,与共聚单体的含量关系不大;不同相对分子质量及组成的POE熔体的黏流活化能相近,约为2.8×10^4 J/mol。基于Carreau、Cross和Arrhenius等方程,分别建立了关联熔体零切黏度与聚合物重均相对分子质量和温度关系的半经验式、关联熔体表观黏度与零切黏度和剪切速率关系的半经验式;两式可用于预测POE熔体的黏度,其适用范围为温度为130~190 ℃,剪切速率为10~2 000 s-1,重均相对分子质量（Mw）为4.2×10^4~1.24×10^5 g/mol。     

Rheological and mechanical properties in polyethylene blends

Melt rheology and mechanical properties in linear low density polyethylene (LLDPE)/low density polyethylene (LDPE), LLDPE/high density polyethylene (HDPE), and HDPE/LDPE blends were investigated. All three blends were miscible in the melt, but the LLDPE/LDPE and HDPE/LDPE blends exibiled two crystallization and melting temperatures, indicating that those blends phase separated upon cooling from the melt. The melt strength of the blends increased with increasing molecular weight of the LDPE that was used. The mechanical properties of the LLDPE/LDPE blend were higher than claculated from a simple rule of mixtures, whiele those of the LLDPE/HDPE blend conformed to the rule of mixtures, but the properties of HDPE/LDPE were less than the rule of mixtures prediction.     

Biaxial orientation of linear polyethylenes using the compressive deformation process

The tensile properties of three grades of linear polyethylene were enhanced by a factor of as much as 15 using a melt/solid phase compressive deformation process that produced equi-biaxial planar orientation in the sheet. Ultra high molecular weight polyethylene with planar isotropy and an in-plane modulus of 10 GPa and a tensile strength of 330 MPa was produced using this method. It was found that the molecular weight had a significant influence on the optimum processing temperature, the ultimate biaxial deformation ratio and hence the ultimate tensile properties. High density polyethylene processed under ideal conditions had a tensile modulus of 2.3 GPa and a tensile strength of 250 MPa. The tensile strength increased linearly with increasing biaxial deformation ratio and the tensile modulus increased non-linearly with increasing biaxial deformation ratio. The deformation rate and the dwell time did not have a significant effect on the tensile properties. Shrinkage tests showed that biaxial deformation was less effective than uniaxial deformation in inducing orientation of the polymer chains, however differential scanning calorimetry results were consistent with the presence of extended chain crystals in very highly oriented ultra high molecular weight polyethylene sheets.