聚乙烯收缩膜的吹塑工艺研究

通过在聚乙烯吹塑加工过程中改变吹胀比、牵引比、霜高线高度等工艺条件,考察其对收缩率的影响;并引人膜泡冷却时间的概念,以量化这些工艺条件的影响。结果表明,薄膜纵、横向拉伸的大小和冷却时间的长短共同决定薄膜的收缩率;拉伸越大,薄膜收缩率越大;膜泡冷却时间越短,薄膜收缩率越大。且膜泡冷却时间为6--10、时,纵、横向收缩率比较适合。     

各种聚乙烯管膜挤出的运动学、动力学和稳定性

本文所述是关于挤出聚乙烯管膜时的运动学、动力学和热传递的基本研究。研究中使用了三种具有流变特征的聚乙烯:低密度聚乙烯(LDPE),线性低密度聚乙烯(LLDPE)和高密度聚乙烯(HDPE)。管膜加工的运动学、稳定性是在宽范围的吹胀比、拉伸比和冷却线高度下进行研究的。求出了沿膜泡方向的局部变形速率;描述了稳定区和非稳定区;测量了张力和充气压力,并用局部伸长粘度表示之;求出了沿膜泡的温度分布并用局部热传递系数加以说明;注明了结晶位置和温度分布,并用来判定结晶速率;比较了LDPE、LLDPE和HDPE的特性。     

HPVC扭结膜吹塑性研究

对HPVC扭结膜吹塑过程进行了研究,推导了膜泡在冷却线处纵、横方向的应力σ_(11t)和σ_(22t)与加工条件的关系式,在无需求出膜厚的条件下,由压折辊处的牵引张力、牵伸比、吹胀比、材料密度、冷却线高度、膜泡内外气压差求出σ_(11t)和σ_(22t)。理论与在各种吹胀比和牵伸比下得到的薄膜性能对比性较好。     

三层共挤聚烯烃热收缩膜(POF)的加工及应用

采用PP作为内外层材料,LLDPE作为中层材料,经三层共挤吹塑形成第一膜管,第一膜管经过加热后进行吹胀拉伸形成第二膜泡,制得三层共挤聚烯烃热收缩膜(POF)。研究了POF的加工工艺,并进行产品性能测试,结果均符合包装要求。具有极高的收缩率和其它类型的热收缩不能比拟的性能,应用范围特别广泛。     

制定LLDPE和LDPE共混料的配方设计出质量更好的薄膜

<正> ——低密度聚乙烯薄膜的主要性能,韧性和牵伸性是随着线形低密度聚乙烯的加入而得到显著改进—— 将线形低密度聚乙烯(LLDPE)混入常用的LDPE中,所生产的薄膜要比LDPE为基本树脂的薄膜韧性和熔体牵伸性方面有所改善(改善程度取决于LLDPE含量)。可在     

二次辐照对交联聚乙烯结构和性能的影响及其应用

研究了辐照对高密度聚乙烯(HDPE)、低密度聚乙烯(LDPE)、线型低密度聚乙烯(LLDPE)、乙烯-乙酸乙烯酯共聚物(EVA)及其共混物性能的影响。将辐照交联后的聚合物经扩张定型后再次辐照,考察了二次辐照对交联结构的影响,并利用二次辐照法制备了一种新型热收缩套管产品。结果表明:随着辐照剂量的增加,样品的凝胶含量增大,拉伸强度先增大后减小,而断裂伸长率则逐渐降低;二次辐照后,样品的形变回复率随着辐照剂量的增加显著降低;所制备的热收缩套管两端收缩率大、中间部分收缩率小,实现了同一制品不同部位收缩倍率的可控性,具有良好的应用前景。     

浅析聚乙烯的生产工艺及进展

介绍了聚乙烯(PE)的主要类型及其应用,着重归纳了高密度聚乙烯(HDPE)、低密度聚乙烯(LDPE)和线型低密度聚乙烯(LLDPE)的生产工艺及各种工艺的最新进展。     

HDPE/LLDPE/CaCO3共混物注射成型收缩率的研究

研究了高密度聚乙烯（HDPE）／线性低密度聚乙烯（LLDPE）共混物及其碳酸钙（CaCO3）填充体系的注射成型收缩率，分别用示差扫描量热仪（DSC）和AR2000高级流变仪分析测定了共混物的结晶度和熔体黏度，并探讨了不同配比下共混物结晶度和熔体黏度与成型收缩率的关系。结果表明，在加工条件不变的情况下，HDPE／LLDPE共混物成型收缩率受结晶度和熔体黏度的显著影响。随LLDPE用量的增加，收缩率的变化明显分为三个阶段，先迅速增大，然后变化减缓，最后又逐渐减小。加入少量铝酸酯活化的CaCO3可以显著降低共混物的成型收缩率。     

聚乙烯生产和市场形势

聚乙烯 (PE)是用量最大的大宗通用树脂，应用广泛，渗入到国民经济各部门，是包装、建筑、农业、电子、交通、日用品工业等的重要基础材料。 PE是乙烯下游中产量最大的品种，约占乙烯消费的 50％左右。 PE包括 LDPE(低密度聚乙烯 )、 LLDPE(线型低密度聚乙烯 )和 HDPE(高密度聚乙烯 )三种，性能各有千秋，有时把 LDPE和 LLDPE一起统计报道。另外，现在有能灵活生产 LLDPE和 HDPE的全密度聚乙烯装置。 PE有良好的力学性能、耐化学性、电性能、卫生性，而且加工容易，价格便宜，是十分重要的化工材料。 1世界 PE生产和消费 1…     

我国聚乙烯市场分析

聚乙烯(PE)指乙烯的均聚物和共聚物,是我国产量最大、消费量最多的塑料原料,主要品种有低密度聚乙烯(LDPE)、线性低密度聚乙烯(LLDPE)和高密度聚乙烯(HDPE)。一、我国PE的生产能力和产量我国从1956年开始生产乙烯,当时日产     

模具流道环流协同LDPE/HDPE吹塑薄膜结构性能研究

通过新型的旋转芯棒薄膜吹塑设备制备了低密度聚乙烯(LDPE)/高密度聚乙烯(HDPE)复合薄膜,并研究了该设备模具流道环流协同作用对吹塑聚乙烯薄膜结构和性能的影响。结果表明,制备的聚乙烯薄膜呈现一种互锁片晶结构;芯棒转速的提高对聚乙烯薄膜样品的结晶度、片晶厚度也有一定增益作用,使得结晶更完善;聚乙烯薄膜的拉伸性能和撕裂性能随芯棒转速提高都有所提升,尤其是横向力学性能,横向拉伸性能最大提升幅度为25.75%,横向撕裂性能最大提升幅度为27.64%;同时,该技术实现了在不影响聚乙烯薄膜的纵向热收缩率的情况下,大幅提高其横向热收缩率,提升幅度可达128.41%。     

An investigation of optical clarity and crystalline orientation in polyethylene tubular film

A study of the crystalline orientation, light transmission, and surface roughness of polyethylene tubular film prepared in our laboratories is presented. The present studies were primarily carried out on low-density (LDPE) and linear-low-density (LLDPE) polyethylene films. The optical properties of a few films of high-density polyethylene (HDPE) prepared for a previous study of morphology were characterized for comparison to the LDPE and LLDPE films. Wide angle X-ray diffraction and birefringence were used to characterize orientation. Both the LDPE and LLDPE films exhibited crystalline texture in which the b-axes tended to be perpendicular to the film surface and the a-axes had some tendency to align with the machine direction. The c-axes tended to be concentrated in the plane of the film with nearly equal biaxial orientation with respect to the machine and transverse directions. Little variation in the crystalline orientation was found with changes of process conditions in the range studied. Birefringence results indicate that the amorphous regions developed an orientation in which the chains tend to be normal to the film surface. The majority of light scattering from these films and a series of HDPE films was from the surface and not from the film interior. The transmission coefficient for the surface contribution was found to be a monotonic decreasing function of the standard deviation of the surface height obtained from surface profiles measured by profilometer. The surface asperites were largest for the HDPE and smallest for the LDPE samples. The intensity of both the surface and interior contributions to the scattering increased with increasing frostline height, i.e., a slower cooling rate. As draw-down ratio and blow-up ratio increase the scattering contribution from the film interior decreases but the contribution from the surface increases somewhat. These effects are discussed in terms of the changes in crystalline morphology and surface roughness produced by flow defects generated during extrusion.     

双峰型LE6592 LLDPE的性能研究

分析了部分第一代聚乙烯和第二代聚乙烯双峰型膜料ＬＥ６５９２ ＬＬＤＰＥ的结晶和流变行为，对比了它们的成膜情况及薄膜性能，总结了ＬＥ６５９２ ＬＬＤＰＥ膜的力学性能随膜厚度、膜泡瓶颈高度及吹胀比变化的规律。     

农用薄型茂金属聚乙烯棚膜的开发与应用

以mLLDPE／LDPE共混树脂为主要原料，采用有膜泡内冷装置的3层共挤复合宽幅吹膜机组和6911／B215耐老化体系生产的薄型茂金属聚乙烯棚膜具有优异的综合力学性能和耐老化性能，应用效果良好。     

Kinematics,dynamics and stability of the tubular film extrusion of various polyethylenes

A basic study of the kinematics, dynamics, and heat transfer occuring during tubular film extrusion of polyethylene is outlined. Three rheologically characterized polyethylenes, a low-density polyethylene (LDPE), a linear-low-density polyethylene (L-LDPE), and a high-density polyethylene (HDPE) were used in this study. The kinematics and stability of the tubular film process were investigated over a wide range of blow-up ratios, drawdown ratios, and frost-line heights. Local deformation rates along the bubble have been determined. Regions of stability and instability are described. Tensions and inflation pressures have been measured and expressed in terms of locol elongational viscosities. Temperature profiles along the bubble were determined and interpreted in terms of local heat transfer coefficients. Positions of crystallization and temperature profiles have been noted and used to estimate rates of crystallization. The characteristics of the LDPE, LLDPE, and HDPE are contrasted.     

Shrinkage in extruded moisture crosslinked silane‐grafted polyethylene wire insulation

Shrinkage studies were conducted on silane‐grafted moisture crosslinkable linear low‐density polyethylene (LLDPE) insulation stripped from extrusion‐coated copper conductors. The insulation, which possesses orientation imparted during melt processing, showed remarkable levels of shrinkage when heated above the melting point of the polymer, though the shrinkage can be greatly reduced by moisture crosslinking the insulation below the melting point of the LLDPE. Shrinkage along the direction of orientation was accompanied by swelling in the other dimensions. Differential scanning calorimetry (DSC) revealed several trends, including a decrease in both melting point and degree of crystallinity with increasing crosslinking. In the first heat after annealing, crosslinked samples exhibited a shoulder in the DSC endotherm several degrees below the normal melting point of the LLDPE. In agreement with prior studies in silane‐grafted HDPE, relaxation of orientation by annealing appeared to result in an increase in the enthalpy of melting. The degree of shrinkage was also found to be dependent on the insulation thickness, which is attributed to faster cooling in thinner insulation immediately following extrusion coating. The results highlight the extensive built in stresses that can be frozen into polymer layers in fabricated articles due to melt orientation. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

扩链改性对聚对苯二甲酸乙二酯挤出吹膜成型的影响

通过添加多官能团环氧扩链剂对聚对苯二甲酸乙二酯(PET)进行扩链改性,然后用改性PET进行吹膜成型,研究了扩链剂含量对PET特性黏度、膜泡稳定性及薄膜力学性能和透明度的影响。结果表明,扩链剂的添加显著提升了PET的特性黏度;随着扩链剂含量的增加,薄膜膜泡稳定性以及表面质量、最大吹胀比、拉伸强度得到显著改善,断裂伸长率呈先增大后减小的趋势。当扩链剂质量分数为0.7%时,PET的特性黏度由纯PET的0.71 d L/g上升至0.94 d L/g,最大吹胀比则由1.9提高至4.5,横纵向拉伸强度分别为61.7 MPa和64.4 MPa,横纵向断裂伸长率达到最高,分别为12%和12.45%,较扩链剂质量分数为0.2%时提高了105.5%以及125.1%,而透光率仅下降1.4%,得到了性能较优的吹塑薄膜制品。     

Barrier property by controlled laminar morphology of LLDPE/EVOH blends

Using the extrusion blown film process, we obtained linear low density polyethylene (LLDPE)/ethylenevinyl alcohol copolymer (EVOH) blends with an improved barrier property by generating a laminar structure of the dispersed phase in the matrix phase. This laminar morphology induced by drawing and blowing was found to result in a significant decrease in toluene permeability with only 10 wt% EVOH. Effects of compatibilizer content and processing parameters such as blending sequence, screw configuration, and stretch ratio on the toluene permeability and morphology of the blends were investigated. It was revealed that the optimum amount of compatibilizer, maleic anhydride grafted LLDPE, should be used to improve the barrier property of the LLDPE/EVOH blends with a well developed laminar structure. The blending sequence had a significant influence on the permeability of the blends. The blend films exhibited a more pronounced laminar structure when all blend components were simultaneously melt blended in a single screw extruder. In addition, the screw configuration designed to impart a low shear stress and the balanced stretching in the machine and transverse directions were more favorable processing conditions in obtaining high barrier blends.     

Transient elongational viscosity of LLDPE/LDPE blends and its relevance to bubble stability in the film blowing process

Transient elongational viscosity of linear low density polyethylene (LLDPE) and its blends with 10% and 20% of low density polyethylene (LDPE) was measured at two temperatures by a constant strain rate elongational rheometer. In addition, the performance of the blends in the film blowing process was assessed in terms of bubble stability at two processing temperatures. An operating window for stable bubble production was determined. The elongational viscosity measurements on blends revealed stronger strain hardening characteristics at a higher temperature of testing. These results correlate favorably with findings from a bubble stability investigation where it was found that the size of the operating window for stable bubble production increased with increasing extrusion temperature. This work seems to indicate that increasing processing temperature during the film blowing of LLDPE-rich blends could lead to a processability improvement of these blends as far as bubble stability is concerned.     

Oriented structure and anisotropy properties of polymer blown films: HDPE, LLDPE and LDPE

Different types of polyethylene blown films (HDPE, LDPE, LLDPE) differ significantly in the ratio between machine and transverse direction tear resistance. In this paper, low density polyethylene (LDPE), linear low density polyethylene (LLDPE) and high density polyethylene (HDPE) blown films at different draw-down ratios are studied, and the relation between crystalline structure and anisotropy of blown film properties is investigated. The crystalline morphology and orientation of HDPE, LDPE, LLDPE blown films were probed using microscopy and infrared trichroism. Significant differences in crystalline morphology were found: at medium DDR HDPE developed a row-nucleated type morphology without lamellar twisting, LDPE showed rod-like crystalline morphology and turned out to the row-nucleated structure with twisted lamellae at high draw-down ratio (DDR), while a spherulite-like superstructure was observed for LLDPEs at all processing conditions. They also showed quite different orientation characteristics corresponding to different morphologies. The morphologies and orientation structure for LDPE, LLDPE and HDPE are related to the stress applied (DDR) and their relaxations in the flow-induced crystallization process, which determine the amount of fibrillar nuclei available at the time of crystallization and therefore, the final crystalline morphology. These structure differences are shown to translate into different ratios of machine and transverse direction tear and tensile strengths.