聚乙烯/聚丙烯共混体系力学性能的研究

研究了线型低密度聚乙烯（LLDPE）／聚丙烯（PP）共混体系、高密度聚乙烯（HDPE）／PP共混体系、超高相对分子质量聚乙烯（UHMWPE）／PP共混体系的力学性能和熔体流动速率。结果表明，UHMWPE的增韧效果最好，在UHMWPE的质量分数为15％时体系的综合力学性能优异，当UHMWPE质量分数大于15％时，材料的综合性能开始下降。     

UHMWPE/HDPE共混体系的流动性和力学性能研究

将一定量超高分子量聚乙烯(UHMWPE)引入高密度聚乙烯(HDPE)中构成共混体系,通过对共混体系的熔体质量流动速率(MFR)、拉伸屈服强度、弯曲性能、冲击强度进行研究,探讨了不同质量分数、不同相对分子质量的UHMWPE对UHMWPE/HDPE共混体系的流动性和力学性能的影响。     

UHMWPE/聚烯烃共混物的性能及其熔融纺丝研究

将超高相对分子质量聚乙烯(UHMWPE)与共混组分聚烯烃(PB)按一定质量比计量,并加入质量分数为0.3%的抗氧剂1010,在双螺杆挤出机上共混造粒,研究了PB的用量对UHMWPE/PB共混物熔点和流变性能的影响;采用实验室熔融纺丝装置对UHMWPE/PB共混物进行纺丝,拉伸得到UHMWPE/PB共混纤维,研究了共混纤维的形貌、结晶性能和力学性能。结果表明:在共混温度为230~290℃时,UHMWPE/PB共混物可实现宏观上均匀共混;共混物具有介于两共混组分熔点之间的单一熔点,共混物熔点随UHMWPE含量的提高而提高;共混物熔体属假塑性流体,270~320℃条件下,随UHMWPE含量的增加,UHMWPE/PB共混物结构黏度指数逐渐增加,黏流活化能逐渐减小,共混物的熔体黏度对温度不敏感;当UHMWPE/PB质量比为1∶1,纺丝温度为310℃时,共混物具有良好的可纺性,经过19倍的后拉伸,所获得的UHMWPE/PB共混纤维直径为45μm,断裂强度可达16.4 c N/dtex,初始模量约190.0 c N/dtex。     

偏心转子挤出机制备LLDPE/UHMWPE共混物的形态、流变行为和力学性能的研究

超高分子量聚乙烯(UHMWPE)和线性低密度聚乙烯(LLDPE)具有相同的分子结构,但很大的黏弹差异使得难以获得相容性较好的共混物。利用由拉伸流场主导的偏心转子挤出机可在较短的加工时间内获得高性能的LLDPE/UHMWPE共混物。扫描式电子显微镜(SEM)表明,UHMWPE可与LLDPE混溶并均匀分布在LLDPE中。差示扫描量热法(DSC)结果表明,随着UHMWPE含量的增加,共混物的熔融温度(T_m)和结晶度(X_c)提高。UHMWPE质量分数为10%、20%、30%、40%和50%的共混物的冲击强度分别是纯LLDPE的1.05、1.2、1.25、1.3和1.4倍,力学性能得以较大程度的提高。研究表明,通过采用偏心转子挤出机(ERE)的拉伸流场加工方法,获得了具有良好相容性和力学性能的LLDPE/UHMWPE共混物。     

UHMWPE/PLA共混体系的制备

利用熔融共混法制备了超高相对分子质量聚乙烯(UHMWPE),聚乳酸(PLA)共混体系,讨论了PLA含量对共混体系熔体流动性能、力学性能、结晶性能及吸水性能的影响.结果表明:随PLA含量的增加,UHMWPE/PLA共混体系的熔体流动性显著增强;体系收缩率下降,尺寸稳定性变好;屈服拉伸强度和缺口冲击强度下降,断裂由韧性断裂逐渐转变为脆性断裂;当w(PLA)为10%时,所制备的共混体系既能保证UHMWPE原有的缺口冲击强度和韧性断裂,又具有较好的熔体流动性能;PLA与UHMWPE共混可加快共混体系的结晶速率,使熔点下降;随着PLA含量的增加,共混体系的吸水率也随之增加.     

UHMWPE/石蜡油溶液体系的黏度特性

以石蜡油(LP)为溶剂配制超高相对分子质量聚乙烯(UHMWPE)/LP溶液,运用正交设计方法,研究低剪切速率下UHMWPE的黏均相对分子质量(Mη)、溶液浓度和温度对UHMWPE/LP溶液体系黏度特性的影响。结果表明:UHMWPE/LP溶液的黏度随Mη及溶液浓度的增加而增加,随溶液温度的升高而降低;正交试验结果为UHMWPE的浓度对UHMWPE/LP溶液体系的黏度影响最大,Mη次之,在190~220℃下,温度影响较小。     

几种不同结构型号PE改性PPR力学性能的研究

研究了线性低密度聚乙烯(LLDPE)/聚丙烯(PPR)共混体系、高密度聚乙烯(HDPE)/聚丙烯(PPR)共混体系、超高分子量聚乙烯(UHMWPE)/聚丙烯(PPR)共混体系的力学性能和熔体流动速率。结果表明,UHMWPE的增韧改性效果最好,在UHMWPE的含量为15%时体系的综合力学性能最好。LLDPE的增韧改性效果次之,HDPE的最差。     

端基对超支化聚合物改性UHMWPE性能的影响

以3种不同端基的超支化聚酯(HBP)分别对超高相对分子质量聚乙烯(UHMWPE)进行共混改性,研究了HBP的端基类型和用量对UHMWPE/HBP共混物力学性能和流变性能的影响。结果表明:随着端羟基超支化聚酯HBP-OH、端苯基超支化聚酯HBP-Bz及端十六烷基超支化聚酯HBP-C16加入量的增大,UHMWPE/HBP共混物的拉伸强度不断降低,断裂伸长率呈现先增大后减小的趋势。在UHMWPE中加入HBP-C16后,共混物的复数黏度呈现上升的趋势。HBP-OH和HBP-Bz的加入量增大能增强UHMWPE大分子链的活动能力,改善了UHMWPE的加工流动性能。     

振动外场对LLDPE/UHMWPE纤维共混体系结晶行为的影响

主要研究了在不同温度下,振动外场对线型低密度聚乙烯(LLDPE)/超高分子量聚乙烯(UHMWPE)纤维共混体系结晶行为的影响。扫描电镜(SEM)分析结果表明,在125℃或150℃下施加振动后,LLDPE/UHMWPE纤维共混体系都形成了串晶结构,而升高温度不利于串晶结构的形成。差示扫描量热分析(DSC)的结果也表明,施加振动后共混体系出现了特殊晶体。广角X射线衍射分析(WAXD)的结果表明,施加振动后共混体系的取向度得到了提高。力学性能测试结果表明,施加振动后共混体系的拉伸强度有所提升。     

UHMWPE/LLDPE/BN复合塑料导热性能研究

将氮化硼(BN)粒子和超高分子量聚乙烯/线性低密度聚乙烯(UHMWPE/LLDPE)分别用熔融辊炼法和粉末混合法制备导热聚乙烯塑料。研究了制备方式、填料含量及偶联剂对填料分散状态及体系热导率、热阻的影响。研究结果表明,粉末法制备的塑料由于BN的高分散效果使得体系的导热性能明显高于熔融辊炼法制备的体系,热导率随填料含量而增加,偶联剂处理有利于提高塑料的热导率。在UHMWPE/LLDPE/BN中添加少量氧化铝短纤维有助于提高体系的力学强度、韧性及热导率。     

Performance of polyethylene/ethylene-vinyl alcohol copolymer/polyethylene multilayer films using maleated polyethylene blends

Blends of linear low density polyethylene (LLDPE) and linear low density polyethylene grafted with maleic anhydride (LLDPE-gMA) were used to promote adhesion between LLDPE and ethylene-vinyl alcohol copolymer (EVOH) in a coextruded three layer flat film, trying to avoid the use of a tie layer. These particular films could be an option when the equipment for a five layer system is not available. The effect of the modified polymer on the surface of cast films was characterized through contact angle measurements. T-peel strength, and oxygen and water vapor transmission rate of the multilayer films were measured as a function of LLDPE-gMA content. Compressed films with 0%, 0.03%, and 0.08% of maleic anhydride (MA) were also analyzed by infrared spectroscopy (FTIR). The increased T-peel strength observed when using MA contents higher than 0.08% suggests a good interfacial adhesion between layers. This increase could be associated with specific interactions between the LLDPE-gMA and the EVOH, as the development of covalent bonds through the reaction of the anhydride with the EVOH hydroxyl groups across the interface. This was proved by the FTIR analysis that showed an increase in the ester band absorbance with an increase on the maleated polymer content and bonding time indicating that a chemical reaction occurred, at the interface. The observed changes on the oxygen and water vapor barrier properties of the films were not significant.     

Cold drawing of polyethylene terephthalate/polyethylene films

Films made from a 77/23 weight percent polyethylene terephthalate/polyethylene blend were stretched using an Instron apparatus. The structures of the samples were examined by methods which included ion beam etching and electron microscopy. The drawn samples exhibited a metallically lustrous and highly reflective surface up to a draw temperature, T_R, of 70°C and a draw ratio of about 5. Under certain conditions the change in structure caused by the stretching resulted in the formation of a highly uniform fibril-void structure. The voids are up to 3 μm in width and 160 μm in length and are formed primarily as a result of aggregation and then separation of the microfibrils of the individual polymer components.     

Positron annihilation in polyethylene and azidosilane-modified glass/polyethylene composites

Positron annihilation lifetime spectra were measured on glass bead-filled high density polyethylene, with a glass content ranging from 0 to 50% by volume. In some cases, the glass beads were surface-modified by different amounts of an azidofunctional alkoxysilane. A composite model for positron annihilation was proposed to account for the observed changes in the relative intensities with increasing amount of filler. A decrease in the intensity of the longest lifetime with increased amount of the silane coupling agent was observed. This suggests a reduction of the free volume in the interphase region between glass and polyethylene, despite a reduction in the crystallinity of the interphase.     

Crystallization kinetics of high-density polyethylene/linear low-density polyethylene blend

This article presents crystallization kinetics studies on a cocrystallizing polymer highdensity polyethylene (HDPE)/linear lowd-ensity polyethylene (LLDPE) blend. The nonisothermal crystallization exotherms obtained by differential scanning calorimetry (DSC) were analyzed to investigate the effect of cocrystallization on kinetics parameters, namely the Avrami exponent and activation energy. The regular change of Avrami exponent with blend composition from a value of about 3 corresponding to HDPE to a value of 2 corresponding to LLDPE is observed. A sheaf-like crystalline growth with variation of nucleation depending on blend composition is concluded from these results of DSC exotherm analysis in conjunction with the small-angle light scattering observations. The observed variation of activation energy of crystallization with blend composition suggests the role of interaction of side chains and comonomer units present in the LLDPE. © 1994 John Wiley & Sons, Inc.     

Crystallization behavior of high-density polyethylene/linear low-density polyethylene blend

Binary blend of high-density polyethylene (HDPE) and linear low-density polyethylene (LLDPE), prepared by melt mixing in an extruder, in the entire range of blending ratio, is studied for crystallization behavior by differential scanning calorimetry (DSC) and X-ray diffraction measurements. Cocrystallization was evident in the entire range of blend composition, from the single-peak character in both DSC crystallization exotherms and meltingendotherms and the X-ray diffraction peaks. A detailed analysis of DSC crystallization exotherms revealed a systematic effect of the addition of LLDPE on nucleation rate and the subsequently developed crystalline morphology, which could be distinguished in the three regions of blending ratio, viz, the “HDPE-rich blend,” “LLDPE-rich blend,” and the “middle range from 30–70% LLDPE content.” Variations in crystallinity, crystallite size, and d spacing are discussed in terms of differences in molecular structure of the components.     

Preparation and properties of polyethylene terephthalate/polyethylene/near infrared reflective pigment composites

Polyethylene terephthalate/high density polyethylene (PET/HDPE) composites containing a near infrared reflective (NIR, nickel antimony titanium yellow rutile) pigment was prepared using ethylene‐glycidyl methacrylate‐vinyl acetate (EGMA‐VA) as a compatibilizer to increase the infrared reflection of PET/HDPE and limit the thermal heat accumulation in light of environmental and energy conservation concerns. HDPE was premixed with NIR to form N‐HDPE masterbatch. A good interfacial bonding between PET matrix and HDPE dispersed phase with the help of compatibilizer was confirmed through Fourier transform‐infrared spectra, scanning electron microscopy, and torque rheometer. For PET/N‐HDPE composites, the major X‐ray diffraction peaks and melting behaviors remained unchanged, indicating the limited alternation of crystalline structure for the composite systems with or without compatibilizer. The observed increment in the crystallization temperature of PET for the investigated PET/N‐HDPE composites was mainly due to the nucleation role of both inorganic NIR and HDPE. Tensile strength and elongation at break for compatibilized cases at various N‐HDPE contents conferred higher values than those of the corresponding counterparts without compatibilizer. Yet, Young's modulus for compatibilized systems was about 40% lower than that for systems without compatibilizer, attributed to the rubbery nature of EGMA‐VA. With the inclusion of NIR into HDPE to form PET/N‐HDPE composites with or without EGMA‐VA compatibilizer, the values of reflectance increased to a great degree. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40830.     

Permeation mechanisms of xylene in blow-molded bottles of pure polyethylene,polyethylene/polyamide and polyethylene/ modified polyamide blends

The hydrocarbon permeation mechanisms of polyethylene/ modified polyamide (PE/ MPA). PE/PA blends and pure PE, were investigated over a range of testing temperatures. In addition to the permeation resistance to xylene, the weight of xylene absorbed per gram of dry polymers (Sx) and the diffusion coefficient (D) of xylene in these bottles were determined. At each fixed testing temperature, the steady permeation rates (Ps) and D of xylene in PE/MPA bottles is significantly lower than those of pure PE bottles, and that of PE/PA bottles is slightly lower. This significantly improved permeation resistance of PE/MPA to xylene at each testing temperature is mainly attributed to the significantly reduced diffusion coefficient of xylene in PE/ MPA bottles, but not due to the slight change in the amount of xylene absorbed in these three bottles. The temperature dependence of steady permeation rates and diffusion coefficient of xylene in each bottle is very similar, and, in fact, some clear transition points were found on the plots of Ps and D versus testing temperatures for PE. PE/PA and PE/MPA bottles. These interesting behaviors along with the temperature dependence of Sx in each bottle were discussed and correlated with the free volume, molecular relaxation motions of these polymers and the vapor pressure of xylene at varying testing temperatures.     

High-pressure phase behavior in polyethylene/n-butane binary and polyethylene/n-butane/CO2 ternary systems

Solubility of polyethylene molecular weight standards (M_w = 2150, 16,400, 108,000, and 420,000 and M_w/M_n = 1.14, 1.16, 1.32, and 2.66, respectively) has been studied in near- and supercritical n-butane and n-butane/CO₂ mixtures at pressures up to 70 MPa. For each polyethylene/solvent system at selected compositions, demixing pressures have been determined using a high-pressure variable-volume view-cell at temperatures up to 200°C. Solutions in pure n-butane are found to display LCST (lower critical solution temperature)-type behavior. The behavior of the solutions in n-butane/CO₂ mixtures are observed to change from the LCST to the UCST (upper critical solution temperature) with increasing CO₂ content in the binary solvent. Sanchez–Lacombe theory has been used to model these systems. The predictions correctly describe the nature of the phase diagrams for both binary and ternary systems and the calculations are in reasonable agreement with experimental data. © 1994 John Wiley & Sons, Inc.     

In situ compatibilization of polystyrene/polyethylene blends using amino-methacrylate-grafted polyethylene

Blends of a styrene–maleic anhydride copolymer (SMA) with polyethlene (PE) or polyethylene melt grafted with tertiary (PE-g-DMAEMA) or secondary (PE-g-tBAEMA) amino methacrylate were prepared by blending in a batch melt mixer. The morphology of these blends at various compositions was examined with a scanning electron microscope (SEM) and related to their tensile and impact properties. The SMA/PE blends are found to have the typical coarse morphology of incompatible blends and poor mechanical properties, while their reactive conterparts, SMA/PE-g-DMAEMA or SMA/PE-g-tBAEMA blends, show finer morphology and modestly improved tensile and impact strength. This was attributed to chemical interaction of the acidic anhydride and the basic amino groups. The greater improvement in morphology for SMA/PE-g-tBAEMA than for SMA/PE-g-DMAEMA suggests a stronger interaction between the secondary amino groups and the anhydride groups, possibly with the formation of SMA-g-tBAEMA-g-PE graft polymer through amide covalent bonds. The amide formation appears to occur at the interfacial region in the blends and is too little to be detected by Fourier transform infrared (FTIR) spectra. However, differential scanning calorimeters (DSC) and the viscosity measurements indicate crystallinity and molecular weight changes for the SMA/PE-g-tBAEMA blends, supporting an argument for the formation of SMA-g-tBAEMA-g-PE grafts at the phase interface.