熔融纺丝法研究LDPE的拉伸流变性能

采用熔融纺丝法研究了低密度聚乙烯(LDPE)熔体的拉伸流变性能。LDPE熔体强度随温度升高而下降;适当降低拉伸黏度可提高熔体的可拉伸性;随拉伸应变速率升高拉伸应力上升,而拉伸黏度下降;拉伸应力和拉伸黏度都随温度的升高呈下降趋势;提高挤出速率可得到较低的拉伸应力和拉伸黏度。     

线性低密度聚乙烯结构与流变特性研究

采用凝胶渗透色谱仪、核磁共振分析仪、旋转流变仪和Rheotens熔体拉伸流变仪分析了线性低密度聚乙烯(LLDPE)和长链支化茂金属线性低密度聚乙烯(mLLDPE)的分子结构与流变特性.结果表明,相对分子质量高、高相对分子质量拖尾和长链支化,可导致聚乙烯(PE)的零切黏度增加、特征松弛时间延长、松弛谱峰变宽、熔体强度提高...     

熔融纺丝法研究聚乙烯熔体的拉伸流变性能

采用熔融纺丝法研究了低密度聚乙烯（PE-LD）、线形低密度聚乙烯（PE-LLD）和高密度聚乙烯（PE-HD）熔体的拉伸流变性能。结果表明,PE-LD、PE-LLD和PE-HD熔体的熔体强度都随温度的升高而下降;随着拉伸应变速率和温度的升高,PE-LD、PE-LLD和PE-HD熔体的拉伸黏度下降;随着挤出速率的提高,相同应变速率下,PE-LD、PE-LLD和PE-HD熔体的拉伸应力和拉伸黏度都有所降低。     

辐照改性制备长支链型高熔体强度聚丙烯流变性能(Ⅱ)拉伸流变

通过辐照法制备了长支链型高熔体强度聚丙烯(LCB-HMSPP),采用Rheotens熔体拉伸流变仪研究了辐照改性PP的熔体强度和拉伸流变行为,讨论了敏化剂含量、辐照剂量、高分子量物质和温度对PP拉伸流变行为的影响。研究结果表明：PP的熔体强度、拉伸应力、拉伸黏度等拉伸流变物理量随敏化剂增加而显著增强,并随辐照剂量呈先上升后下降的趋势,辐照剂量为5kGy时,熔体强度和拉伸黏度到达最大。添加极少量高分子量物质(UHMWPE)也能有效提高PP的熔体强度。LCB-HMSPP的熔体强度活化能显著降低,熔体强度温度敏感性下降,可在较宽的温度范围内表现出较高的熔体强度。     

聚丙烯熔体拉伸流变行为的研究

采用双料筒毛细管流变仪,对两种不同摩尔质量的等规聚丙烯的剪切及拉伸流变行为进行了研究,并采用Cogswell方法计算了熔体的拉伸强度。结果表明：聚丙烯为假塑性流体,随着剪切速率的增加,熔体的表观剪切黏度下降,呈现出假塑性流体典型的“剪切变稀”行为。在相同的温度和剪切速率下,平均摩尔质量较小、分布较宽的聚丙烯的表观剪切黏度及拉伸黏度均较小,但熔体的拉伸强度较大,意味着其具有较好的流动性能,并具有较高的可拉伸性,可以达到较大的拉伸比。     

熔体拉伸PE–HD和PE–LLD薄膜的制备及性能

以高密度聚乙烯(PE–HD)和线型低密度聚乙烯(PE–LLD)树脂为原料,采用转矩流变仪,借助熔体拉伸法制备了具有取向结构的PE–HD膜和PE–LLD膜。利用偏光显微镜、傅立叶变换红外光谱、差示扫描量热、小角激光散射及力学性能测试分析不同熔体拉伸速率下PE–HD膜和PE–LLD膜的结构与性能变化情况。结果表明,熔体拉伸速率越高,PE–HD膜和PE–LLD膜的相对取向度越高,快速拉伸PE–HD膜和PE–LLD膜的相对取向度分别为2.043和1.556;熔体拉伸速率对PE–HD膜和PE–LLD膜的结晶温度影响不大,两种膜具有显著的结晶性,PE–HD膜的结晶性更好;随熔体拉伸速率的提高,PE–HD膜和PE–LLD膜的拉伸屈服应力和拉伸弹性模量提高,断裂伸长率降低,总体上看,PE–LLD膜的断裂伸长率较PE–HD膜高,而拉伸强度较PE–HD膜低。     

PP/CPE共混性能研究

研究了氯化聚乙烯(CPE)用量对聚丙烯/氯化聚乙烯(PP/CPE)材料的熔融时间、扭矩、表观黏度、氧指数和拉伸强度的影响,并通过扫描电镜研究了共混物的拉伸断面结构。结果表明:熔体最大扭矩和熔融时间随着CPE用量的增加而下降,而平衡扭矩和表观黏度上升,当CPE质量分数介于33%～45%之间时达到最优配比。另外,随着CPE用量的增加,共混物的阻燃性能显著增加,但拉伸强度在CPE质量分数大于20%后稍有下降。     

HDPE管材专用树脂的流变性能

应用动态流变仪、毛细管流变仪和转矩流变仪,对新型双峰高密度聚乙烯(HDPE)管材专用树脂 6380 M进行流变性能测试分析,并与国内外相同压力等级的HDPE管材专用树脂进行比较。结果表明,6380 M的各种流变性能与进口管材专用树脂相当,而与单峰HDPE管材专用树脂相比具有弹性模量低、零切黏度低、拉伸黏度低的流变特性,从而对其加工性能产生影响。6380 M流动性好,其临界剪切速率高,但熔体强度不及单峰HDPE。     

双向拉伸聚乙烯薄膜专用料的结构剖析

利用凝胶渗透色谱仪(GPC)、差示扫描量热仪(DSC)和核磁共振波谱仪(NMR)等对2种进口双向拉伸聚乙烯(BOPE)薄膜专用料(SP3022和TF80)和国产茂金属线型低密度聚乙烯(mLLDPE)薄膜专用料(EZP2010HA)的结构和性能进行了分析对比。结果表明：与EZP2010HA相比,SP3022和TF80的熔体流动速率更低,相对分子质量及其分布更宽,密度、熔融温度、结晶温度、结晶度均更高,厚晶片含量更多,剪切黏度更小,更适合双向拉伸加工。     

聚对苯二甲酸丙二酯熔体拉伸流变性能研究

使用毛细管流变仪研究了PTT熔体在单轴拉伸流场中的流变性能。结果表明,PTT熔体拉伸流动属于拉伸变稀型,熔体的拉伸粘度随拉伸应力增加而降低,随相对分子质量提高,熔体的拉伸变稀现象更加明显。熔体的相对分子质量越高,拉伸速率对熔体的拉伸粘度影响越大。随拉伸速率提高,熔体的拉伸应力增大,拉伸粘度减小,易产生拉伸共振现象。因此,PTT熔体纺丝时应该采取较低的喷头拉伸倍数,即适当提高熔体挤出时的纺丝速度,或降低卷绕速度,以此降低熔体拉伸比和防止拉伸共振现象,改善纺丝成形的稳定性。     

DYNAMICALLY VULCANIZED THERMOPLASTIC ELASTOMER BLENDS OF NATURAL RUBBER AND POLYPROPYLENE

Dynamic vulcanization of a soft grade of thermoplastic natural rubber (TPNR) was carried out using several concentrations of Hexamethylene N, N′ bis (tert-butyl peroxy carbamate) (HBTP). The blends were melt mixed in a Brabender plasticorder. The effectiveness of dynamic vulcanization was investigated using the Brabender plastograms, swelling index measurements, rheological behavior by means of a capillary rheometer, dynamic mechanical properties, and tensile testing. It was found that varying the HBTP concentration had a great influence on the rheological behavior as well as the dynamic and tensile properties of the material. The increase of HBTP dosage resulted in an increase of the extent of crosslinking and caused an increase of the elastic modulus and a reduction of the loss modulus. The ultimate tensile strength and elongation at break also increased with increasing HBTP loading. The rheograms indicated that the blends exhibit a pseudoplastic behavior.     

TDI/BPO改性PBS的力学性能研究

本文采用扩链手段和交联手段对PBS进行改性研究。分别选用甲苯2,4-二异氰酸酯(TDI)为扩链剂,过氧化苯甲酰(BPO)为交联剂。使用乌氏黏度计、索氏抽提器对改性体系的特性黏数和交联度进行测定;使用哈克转矩流变仪、毛细管流变仪、差示扫描量热仪、万能拉力测试机等手段测试了改性体系的加工性能,流变性能,结晶与热性能,以及力学性能等。研究了扩链剂和交联剂用量对改性体系性能的影响。结果表明,随着TDI用量的增加,PBS改性体系的特性黏数逐渐增大,加工体系的平衡扭矩提高,熔体黏度呈现出增大的趋势,从而熔体强度增大。通过扩链反应,结晶温度提高,结晶度降低,熔点升高,拉伸强度变化不大,当TDI用量为1.0%时,拉伸强度最大。随着BPO用量的增加,PBS改性体系的交联度逐渐增大,加工性能得到改善,熔体黏度大幅提高,从而熔体强度增大。交联度的增大使得改性体系的结晶温度提高,结晶度和熔点均降低,拉伸强度呈现出先增大后减小的趋势。     

塑料网套专用LDPE树脂结构与性能的研究

分析了发泡工艺过程及其对原料的要求,对发泡网套用低密度聚乙烯(LDPE)2420H的结构性能、流变性能进行了分析研究,并与进口产品进行了对比。结果表明:2420H的重均分子量较小,分子量分布较窄,支化度低于对比样,使得2420H的熔体强度较低,熔体黏度较小,导致制品回弹性损失过快,需适当提高2420H的支化度以增加熔体强度。     

SEBS-g-MAH增韧聚乳酸的性能研究

采用哈克密炼机制备了聚乳酸(PLA)与马来酸酐接枝苯乙烯-乙烯-丁二烯-苯乙烯嵌段共聚弹性体(SEBS-g-MAH)的共混物,并对共混物的力学性能、流变性能和微观结构进行了分析。结果表明,共混物的拉伸强度随着SEBS-g-MAH含量的增加而下降,断裂伸长率随着SEBS-g-MAH含量的增加而增大。当SEBS-g-MAH的含量为30 %时,共混物的冲击强度提高了2.5倍,共混物的韧性得到提高。随着SEBS-g-MAH含量的增加,PLA熔体黏度的变化趋势与SEBS-g-MAH越来越相似,即熔体黏度随着频率的增大而下降。扫描电镜分析表明,MAH基团改善了两相间的界面作用,增韧作用明显。     

共聚聚丙烯(cPP)/线型低密度聚乙烯(LLDPE) 共混体系的流变与结晶形为

用毛细管流变仪研究了共聚聚丙烯(cPP)与线型低密度聚乙烯(LLDPE)共混物熔体的流变行为.讨论了共混物的组成、切应力和剪切速率对熔体流变行为和熔体粘度的影响.测定了不同配比共混物熔体的非牛顿指数.结果表明共混物熔体属假塑性流体,但共混体系粘度随LLDPE加入量的增加变化不大.DSC结晶曲线及扫描电镜(SEM)照片表明,LDPE的加入使cPP的结晶温度变化不大,但对晶体形态有一定影响.LLDPE对cPP有一定的增韧改性作用,当LLDPE质量分数为15%时,共混物的冲击强度增幅在40%左右,而拉伸强度保持率为80%.     

The characterization of rheological properties of melt grafting polypropylene for foaming

Large enhancements of the melt strength of polypropylene (PP) were achieved by the introduction of specific unsaturated linear polyester (ULP) branches using melt grafting. The transient torque curves and optical rheology microscope images indicated that branching reactions took place and the ULP had been grafted onto the PP backbone. Shear rheological behaviors of three kinds of PP were investigated using rotational rheometer under dynamic shear mode with periodic shear rate. These PP samples are foamable PP (FPP) with sparse branches obtained by grafting ULP, commercial high melt strength PP (HMS PP) for foaming and conventional linear PP (EPS). It was found that the rheological properties of FPP, the HMS PP, were distinctly different from those of conventional PP. Storage modulus, steady state compliance and zero shear viscosity increased in comparison with EPS, while shear viscosity decreased. This result implied the presence of branching structures that was not revealed in conventional PP. In melt flow measurements, extrusion swell that was a prominent behavior of branching PP was observed also for FPP and PF. Compared to linear PP, FPP and PF showed distinct sag-resistant property and lower melt flow index. On the other hand, to estimate the extent of branching, a detailed method was applied using the obtained zero shear viscosity. The result showed that FPP was grafted by sparse ULP. From these results, it was found that FPP showed obvious enhancements in rheological behaviors similar to PF, although its melt strength was lower than that of PF due to the presence of shorter branching chains grafted on the backbone of FPP.     

共聚聚丙烯／茂金属线形低密度聚乙烯共混体系的流变行为与结晶行为

用毛细管流变仪研究了冲击性能相对优良的共聚聚丙烯(cPP)与茂金属低密度聚乙烯(m-PE—LLD)共混物熔体的流变行为。讨论了共混物的组成、剪切应力和剪切速率对熔体流变行为、熔体粘度的影响。测定了不同cPP及m—PE—LLD配比的共混物熔体的非牛顿指数。结果表明：共混物熔体属假塑性流体，但其粘度随m—PE—LLD加入量的增加变化不大。DSC分析及微观形态分析表明，m-PE—LLD的加入使cPP的结晶温度提高，具有异相成核作用。m-PE—LLD对cPP有明显的增韧作用，当m—PE—LLD含量为15％时，共混物的冲击强度明显提高，增幅在75％左右，而拉伸强度保持率为85％以上。     

The effect of polypropylene/polyamide 66 blending modification on melt strength and rheologic behaviors of polypropylene

Common linear polypropylene (PP) was modified by blending with polyamide 66 (PA66) under the act of compatibilizer in a twin-screw extruder in an attempt to improve the melt strength (MS) of PP. The MS of pure PP and modified PPs were measured by MS testing unit at three temperature of 190, 210, and 230 °C, and the MS improvement of PP was verified. The MS of the modified PPs increased with increasing the content of PA66. The steady- and dynamic-shear rheological behaviors of pure PP and modified PPs were investigated using a capillary rheometer and a parallel-plate rotating rheometer. The steady-shear rheological analysis results revealed that modified PPs had higher melt shear viscosity, stronger non-Newtonian behaviors, and higher zero shear-rate viscosity. The dynamic-shear rheological analysis showed modified PPs had higher melt complex modulus and smaller phase angle, which indicated that the melt viscosity and melt elasticity of PP were also enhanced. The modified PPs was characterized by DSC. DSC results revealed that the PA66 phase and PP phase of the modified PPs were in state of crystallization. The enhancement of MS, melt viscosity, and melt elasticity of modified PPs could be due to undisaggregated PA66 crystallization phase within the melt of PP blends.