矿脂对UHMWPE的结晶和流变行为的影响

使用矿脂作为新型溶剂溶胀超高摩尔质量聚乙烯(UHMWPE),利用熔融共混制备了不同矿脂含量的UHMWPE/矿脂凝胶,通过扫描电子显微镜、示差扫描量热分析仪和流变仪测试分析了矿脂含量的不同对凝胶体系的形貌、结晶行为和流变行为的影响。结果表明,矿脂含量的增加可提高UHMWPE分子链网络的溶胀水平,减少链间缠结,增加自由链数量,进而UHMWPE体系的弹性模量减小,结晶速率加快,加工性能提高。     

高温熔融对UHMWPE/c-HDPE共混物界面扩散的促进作用

以摩尔质量低且分子链运动能力强的自制c-HDPE为基体,将其与少量的超高摩尔质量聚乙烯(UHMWPE)共混,之后再施加高温熔融(HTM)处理,同时结合红外光谱(FTIR)、差示扫描量热仪(DSC)、旋转流变仪以及扫描电子显微镜(SEM)等手段探究高温熔融处理对于UHMWPE/c-HDPE共混物界面扩散作用的影响。结果表明,高温熔融处理的确能够促进UHMWPE分子链解缠结,并加速UHMWPE分子链扩散进入c-HDPE基体相之中。这种变化将最终影响共混物的结晶和流变行为以及共混物中的两相形态。     

HDPE/UHMWPE共混物的制备及其性能

采用不同螺纹块组合的双螺杆挤出机制备HDPE/UHMWPE共混物,研究UHMWPE用量、螺杆结构对共混物力学性能、流变行为及分散形态的影响.结果表明:随着UHMWPE用量的增加,共混物的拉伸和缺口冲击强度随之增加,特殊螺杆挤出机制备共混物的机械性能均比普通螺杆的提高.UHMWPE使共混物成型加工黏度增大,特殊螺杆能降低共混物成型加工黏度.偏光显微镜照片显示,特殊双螺杆挤出机使UHMWPE熔融程度和分散程度增大.     

不同成型方式下UHMWPE耐热改性进展

介绍了近年来超高分子量聚乙烯(UHMWPE)在模压成型、挤出成型、注塑成型方面的耐热改性研究进展,分析了采用不同成型方法对UHMWPE耐热改性的方法及改性效果。关于UHMWPE模压与挤出成型的耐热改性方法主要包括物理改性(填充改性、共混改性、共混填充改性)、化学改性(过氧化物交联、偶联剂交联、辐射交联)、聚合填充复合改性,而UHMWPE的注塑成型耐热改性研究较少。对UHMWPE进行耐热改性,加入的改性材料后,能显著提高复合材料耐热性,但是,部分材料的加入却降低了UHMWPE耐磨性、抗冲击性等性能,需要对UHMWPE注塑成型的耐热改性及改性材料的选用进一步研究。最后,对UHMWPE的耐热改性的发展趋势进行了展望。     

不同流场对聚乙烯蜡/UHMWPE体系结构与性能的影响

选取低分子量聚乙烯蜡(PE-wax)作为解缠结助剂,研究不同流场对超高分子量聚乙烯(UHMWPE)缠结程度的影响规律,分别利用推拉混炼仪与转矩流变仪对PE-wax/UHMWPE进行熔融共混,研究不同加工时间下拉伸流场与剪切流场对复合体系的微观结构与宏观性能的影响。结果表明,在剪切流场作用下,随着塑化混炼时间的增加,体系缠结度逐渐增加,复合体系的拉伸性能呈现先上升后下降的趋势。在拉伸流场的作用前期,UHMWPE初生态粒子规整的分子链结构被破坏,缠结程度升高,其塑化混炼效率高于剪切流场;而在拉伸流场的作用后期,UHMWPE分子链解缠结速率高于缠结速率,缠结程度下降,结晶度与熔点升高,样品的可拉伸性提高。     

UHMWPE/HDPE共混物的流动性及力学性能的研究

采用不同MFR的HDPE与UHMWPE进行熔体共混。结果表明UHMWPE／HDPE共混物流动性和力学性能的变化受体系组成、熔体粘度比等因素的影响较大。HDPE的MFR过高、过低或用量过多，均不利于共混物流动性及综合力学性能的改善。当HDPE作为分散相时，易于实现向UHMWPE高粘弹粒子的渗透、分散及结合，共混物的．MFR及拉伸屈服强度、断裂强度、断裂伸长率均比UHMWPE有提高，共混物表现出协同效应；当UHMWPE为分散相或二者熔体粘度比差异过大时，混合效果变差，共混物综合力学性能下降；在某些中间配比下，二者表现出增链缠结效应，共混物MFR明显降低。     

HDPE-g-MAH对PA6/UHMWPE共混合金力学性能及结晶行为的影响

采用HDPE-g-MAH作为相容剂来增容PA6/UHMWPE共混合金。结果表明:在熔融共混过程中HDPE-g-MAH和PA6发生化学反应,生成的接枝聚合物对PA6/UHMWPE产生增容作用。加入HDPE-g-MAH共混体系的界面形态和力学性能均有较大的改善,吸水率也有所下降。通过Mo-lau实验I、R、SEM观察来研究其在熔融共混过程对PA6/UHMWPE的反应增容作用。采用DSC实验对PA6/UHMWPE共混合金进行了结晶性能测试,随着HDPE-g-MAH用量的增加,UHMWPE结晶度增加,而PA6的结晶度降低。     

超高分子量聚乙烯(UHMWPE)的加工成型及共混改性

本文讨论了 UHMWPE 的几种加工成型方法,包括压制烧结成型、挤出成型、注射成型及吹塑成型等,并讨论了提高 UHMWPE 熔融流动性能的共混改性途径。     

改性HNTs对UHMWPE力学性能、热学性能的影响

为进一步获得高性能的超高分子量聚乙烯（UHMWPE）材料，以有机物乙酸钾为改性剂改性埃洛石纳米管（HNTs），制备杂化HNTs。通过熔融混合后模压的方式制备不同改性HNTs含量的UHMWPE/HNTs纳米复合材料。研究改性剂对HNTs结构的影响及改性HNTs对复合材料力学性能与热稳定性的影响。结果表明：乙酸钾增加了HNTs的层间距，弱化分子内的作用力。改性HNTs的用量为3 g时，复合材料的拉伸强度最大，为25.5 MPa。改性HNTs用量5 g时，复合材料的断裂伸长率和冲击强度较未加入HNTs时分别下降了20%和3.3%；弯曲强度和维卡软化点较未加入HNTs时分别提高1 MPa、3.5℃。改性HNTs的加入提高了UHMWPE的热稳定性及部分力学性能。     

UHMWPE/PP的共混改性

采用自行配制的解缠剂Jc 3降低UHMWPE的熔体粘度,并用机械共混的方法进行加工,从而实现PP与UHMWPE之间的均匀共混,以改善共混体系的力学性能。研究了原料配方及加工工艺对共混体系力学性能的影响。结果表明:解缠剂能够有效改善共混体系的混合程度;UHMWPE的用量和Jc 3的用量对共混物力学性能有不同的影响;采用先开炼再挤出而后注射的加工工艺得到的制品力学性能较好。     

Influence of poly(ethylene glycol)‐containing additives on extrusion of ultrahigh molecular weight polyethylene/polypropylene blend

The influence of poly(ethylene glycol) (PEG)‐containing additives on the extrusion behavior of ultrahigh molecular weight polyethylene/polypropylene (UHMWPE/PP) blend was studied. It was found that the addition of small amounts of PEG to UHMWPE/PP blend resulted in significant reduction of die pressure and melt viscosity, and obvious increase of the flow rate at a given die pressure, while PEG/diatomite binary additives enhanced the improvement in the processability of UHMWPE/PP blend. When pure HDPE was extruded with the die through which UHMWPE/PP/PEG blend was previously extruded, the extrusion pressure of HDPE increased with the extrusion time gradually. This meant that PEG might migrate to the die wall surface and coat it in the extrusion of UHMWPE/PP/PEG blend. FTIR spectra and SEM micrographs of the UHMWPE/PP/PEG extrudates indicated that PEG located not only at the surface but also in the interior of the extrudates. So, the external lubrication at the die wall, combined with the internal lubrication to induce interphase slippage of the blend, was proposed to be responsible for the reduction of die pressure and viscosity. In addition, an ultrahigh molecular weight polysiloxane and a fluoropolymer processing aid were used as processing aids in the extrusion of UHMWPE/PP as control, and the results showed that only minor reduction effects in die pressure and melt viscosity were achieved at their suggested loading level. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1282–1288, 2006     

Exploring the entangled state and molecular weight of UHMWPE on the microstructure and mechanical properties of HDPE/UHMWPE blends

Three types of ultra-high molecular weight polyethylene (UHMWPE) with different entangled state and molecular weight were blended with high-density polyethylene (HDPE) matrix by melt blending. Rheology, 2D-SAXS, 2D-WAXD, DSC, and mechanical tests were used to study the evolution and difference of microstructure and mechanical properties of the blends. The addition of weakly entangled UHMWPE enhanced the chain diffusion and chain orientation ability under a specific flow field. Thus, the rheological properties and mechanical properties of the blends were improved with the mix of weakly entangled UHMWPE. The mechanical properties enhancement effect of HDPE/UHMWPE blends with weakly entangled UHMWPE was owing to the shish-kebab structure formed in the injection molding process. The molecular chains of UHMWPE with a low degree of entanglement and high molecular weight increased the lamella size and crystallinity of the blends during processing. This leads to the formation of more oriented shish structures and more kebab lamella. Besides, the molecular chains of weakly entangled UHMWPE were better interlocked and intertwined with other polyethylene chains in the amorphous region, acting as the tie molecules, significantly improving the impact resistance.     

双柱塞超高分子量聚乙烯特殊挤出成型工艺研究

介绍了超高分子量聚乙烯的熔体特性,如粘度极高、熔体指数几乎为零、摩擦因数小、临界剪切速率低等,给成型加工带来了很大的困难。针对其特殊性采取特殊的挤出成型工艺(复合挤出、双柱塞式挤出)。挤出时脉动小、加热快,并且可以挤出分子量不同纯超高分子量聚乙烯制品。     

Preparation of HDPE/UHMWPE/MMWPE blends by two-step processing way and properties of blown films

Summary Blends of high density polyethylene (HDPE) and ultra high molecular weight polyethylene (UHMWPE) were prepared by two-step processing way. Middle molecular weight polyethylene (MMWPE) as a fluidity modifier and compatilizer was added into UHMWPE in the first step, and then modified UHMWPE and HDPE were blending extruded to prepare the HDPE/UHMWPE/MMWPE blends used for blown films. The mechanical test of the blown films revealed that when the content of MMWPE in modified UHMWPE was 40wt% and the content of UHMWPE in the blends was 20 wt%, the film had the optimal mechanical properties. The tensile strength and tear strength of the film increased by 50% and 21%, respectively, compared with those of pure HDPE film. Rheological curves indicated that the melt torque and the apparent viscosity of the HDPE/UHMWPE/MMWPE blends made by two-step processing way both greatly reduced than other blends. The results from DSC suggested that the blends by two-step processing way may form more stable and perfect co-crystallization. PLM (polarized light microscopy) and SEM micrographs revealed that two-step processing way can improve the surface morphology of the films and make the dispersion of UHMWPE particles in HDPE increase.     

PP／UHMWPE原位成纤复合材料的混炼及成型工艺研究

采用超高分子量聚乙烯（ＵＨＭＷＰＥ）原位成纤增强、增韧聚丙烯（ＰＰ）。讨论了混炼剪切力、成型冷却方式和ＵＨＭＷＰＥ熔体熔点粘度对材料力学性能的影响。发现提高剪切力,加快冷却速度均有利于力学性能的提高,配比为９０／１０的ＰＰ／ＵＨＭＷＰＥ的缺口冲击强度、拉伸强度和断裂伸长率可达８８．６ｋＪ／ｍ＾２、４５．１ＭＰａ和５７０％,分别是ＰＰ－１３３０的３．５倍、１．５倍和２．５倍;而ＵＨＭＷＰＥ相对分子擀     

Dispersion of carbon nanotubes in ultrahigh‐molecular‐weight polyethylene by melt mixing dominated by elongation stress

A novel melt‐mixing method and corresponding mixer for polymer materials are reported. The effects of carbon nanotube (CNT) loading, rotation rate and mixing time on the morphology and properties of CNTs/ultrahigh‐molecular‐weight polyethylene (UHMWPE) nanocomposites were experimentally investigated in detail using the mixer. Homogeneous dispersion of CNTs in intractable UHMWPE is successfully realized without the aid of any additives or solvents. Differential scanning calorimetry results showed that the crystallinity increases 13.8% when 1 wt% of CNTs is added into the composites. The maximum crystallinity increased 13.5% and then decreased slightly with increasing rotation rate. The mixing time had little effect on crystallinity. Rheological tests reveal that the effect of CNT loading on the storage modulus/complex viscosity is a result of competition between the viscosity decrease due to the selective adsorption of UHMWPE onto CNT surfaces and the viscosity increase caused by the formation of an interconnected polymer–nanotube network. The storage modulus/complex viscosity decreased with increasing rotation rate/mixing time. This is a synergic result of the selective adsorption of the long molecular chains onto the CNT surface and their thermomechanical degradation. The results showed that the mixing process dominated by elongation stress is a simple, efficient green way to prepare CNTs/UHMWPE nanocomposites via melt mixing. © 2018 Society of Chemical Industry     

UHMWPE对有机PTC复合材料的稳定作用

利用传统的熔融－混合方法制备碳黑填充的聚丙烯（PP）／超高分子质量聚乙烯（UHMWPE）复合材料，当P／UHMWPE质量比大于3／7时，碳黑填充PP／UHMWPE复合物的正温度系数（PTC）和负温度系数（NTC）效应类似于碳黑填充的纯PP聚合物，但当质量比等于或小于3／7时，复合物所表现的PTC效应非常相似于碳黑填充充的纯UHMWPE聚合物，在复合物中采用粘度非常高的聚合物作为一种组分可以有效消除NTC效应。     

聚合填充型超高分子质量聚乙烯复合材料的结构与性能

介绍了采用聚合填充工艺,分别以硅藻土、高岭土为填料,制成的超高分子质量聚乙烯复合材料。结构形态研究表明,该复合材料中填料粒子与聚合物基体之间界面结合力以及填料粒子的分散性均好于共混型材料。该复合材料不但保持了超高分子质量聚乙烯的绝大多数优点,还大大弥补了它的一些不足。     

Well-mixed blends of HDPE and ultrahigh molecular weight polyethylene with major improvements in impact strength achieved via solid-state shear pulverization

Compared with conventional polyolefins, ultrahigh molecular weight polyethylene (UHMWPE) possesses outstanding impact strength and crack resistance that make it desirable for a wide variety of applications. Unfortunately, UHMWPE has an ultrahigh viscosity that renders common, continuous melt-state processes ineffective for making UHMWPE products. Attempts to overcome this problem by blending UHMWPE with lower molecular weight high-density polyethylene (HDPE) by melt processing have typically led to poorly dispersed blends due to the vast viscosity mismatch between blend components. Here, we present solid-state shear pulverization (SSSP) as a mild, continuous, and simple approach for achieving effective and intimate mixing in UHMWPE/HDPE blends. These SSSP blends are easily processed by post-SSSP melt extrusion; for an SSSP blend with 50 wt% UHMWPE, we observe more than a factor of 1000 increase in viscosity at a shear rate of 0.01 s⁻¹ but less than a factor of 5 increase at 100 s⁻¹, the latter being more typical of melt-processing operations. Using extensional rheology, we confirm the strain hardening behavior of SSSP blends. Shear rheology and crystallization data show that the mixing between UHMWPE and HDPE can be improved with subsequent passes of SSSP and single-screw extrusion. Finally, we show that blending via SSSP leads to dramatic improvements in impact strength: as compared to literature results, injection-molded sample bars made from SSSP blends with 30–50 wt% UHMWPE exhibit very high values of notched Izod impact strength, 660–770 J/m (the impact strength of neat HDPE was 170 J/m).     

超高分子量聚乙烯对有机PTC复合材料的超强稳定作用研究

利用传统的熔融 混合方法制备碳黑填充的聚丙烯 (PP) /超高分子量聚乙烯 (UHMWPE)复合物。当PP/UHMWPE混合比大于 3 / 7,碳黑填充PP/UHMWPE复合物的PTC和NTC效应类似于碳黑填充的纯净PP聚合物。然而当重量比等于或小于 3 / 7时 ,复合物所表现的PTC效应非常相似于碳黑填充的纯净的UHMWPE聚合物。在复合物中应用粘度非常高的聚合物作为一种组分可以有效消除NTC效应