原位交联改性PP/POE共混物的等温结晶行为

采用热塑性聚烯烃弹性体(POE)作为增韧材料,以过氧化二异丙苯(DCP)为交联剂制备了PP/POE共混物。利用差示扫描量热仪(DSC)和偏光显微镜(PLM)研究了PP/POE共混物等温结晶行为,并用Avrami方程分析了PP/POE共混物结晶动力学。结果表明,POE的加入能起到异相成核的作用,加快了PP的结晶成核速率。Avrami指数在1.93～3.09,DCP的引入对聚丙烯(PP)的成核与生长机理影响不大,但其原位交联作用阻碍了PP分子链的运动,使得PP结晶速率降低,结晶时间延长。     

PP/POE共混物的热行为与晶态结构

采用双螺杆挤出机熔融共混制备了不同组成的聚丙烯(PP)/乙烯-辛烯弹性体(POE)共混物,利用差示扫描量热仪、偏光显微镜和广角X射线衍射系统研究了共混物的热行为与晶态结构。结果表明PP与POE之间具有一定的相容性,POE的异相成核作用提高了共混物中PP的结晶温度和结晶速率,有效地诱导β晶型PP的形成,增大了共混物中α晶型和β晶型PP的晶面表观厚度。另一方面,由于POE与PP之间存在较强的相互作用,POE大分子链使PP分子链的扩散和堆积受阻,从而导致PP/POE共混物总结晶度的降低。     

UHMWPE／LDPE共混物的结晶行为与力学性能

采用差热分析和相差显微镜方法研究了超高分子量聚乙烯(UHMWPE)与低密度聚乙烯(LDPE)的机械共混物的结晶行为及其力学性能。在所采用的单螺杆挤出共混条件下,UHMWPE基本上以填料方式被分散于LDPE基体中。两组分没有共结晶发生,熔体长时间热处理可使两组分相互作用增加,UHMWPE可使LDPE的屈服强度和模量增加,辊筒共混方法得到的共混物性能优于单螺杆挤出的共混物的性能。     

PTT/POE-g-MAH共混合金的流变行为和结晶熔融性能

利用毛细管流变仪、热台偏光显微镜(POM)和差示扫描量热仪(DSC),分别研究了聚对苯二甲酸丙二酯(PTT)/马来酸酐接枝乙烯-辛烯共聚物(POE-g-MAH)共混合金的流变行为、结晶形态和热性能。结果表明,PTT/POE共混合金熔体为假塑性流体,POE组分含量越高,共混合金对剪切速率变化越敏感,表观黏度降低越多,POE有一定的增塑作用;由于POE与PTT间的相互作用,共混合金从熔体结晶时形成的PTT晶体尺寸明显减小,但体系起始结晶温度升高,结晶速度加快。在Tg以上,由于POE的影响,PTT组分的冷结晶焓变迅速减小。当POE组分含量超过4%时,体系中出现POE的聚集体,相分离明显。     

增容剂对回收聚对苯二甲酸乙二醇酯/乙烯-辛烯共混物结晶性能的影响

以甲基丙烯酸环氧丙酯接枝乙烯-辛烯共聚物(mPOE)为增容剂对回收聚对苯二甲酸乙二醇酯(r-PET)/乙烯-辛烯共聚物(POE)共混物进行增容改性。用HAAKE流变仪、差示扫描量热仪(DSC)、广角X射线衍射(WAXD)分别研究了不同mPOE含量对r-PET/POE共混物的扭矩变化和接枝共聚物对PET结晶性能的影响。结果表明,共混物的扭矩随着mPOE含量的增加而增大,即mPOE与r-PET生成的接枝共聚物POE-g-PET含量增大。DSC和WAXD结果表明,POE对PET有异相成核作用,而POE-g-PET共聚物对PET结晶有一定的阻碍作用。     

PP/POE共混物的毛细管和转矩流变行为

利用高压双管毛细管流变仪和Haake转矩流变仪研究了聚丙烯(PP)/乙烯-辛烯共聚物(POE)体系的流变行为,探讨了转速、剪切速率、温度及共混物的组成对熔体流变行为的影响。结果表明,两种方法所测得的熔体流变学结果基本一致,共混物熔体表现为假塑性流变行为。随着POE含量的增加,PP/POE共混物熔体的表观黏度和非牛顿指数表现为负偏差行为,粘流活化能则表现出正负偏差行为,说明PP与POE之间存在一定的相容性。     

新型无卤膨胀阻燃低密度聚乙烯复合材料的非等温结晶动力学

通过熔融混合将有机杂环磷酸酯1,3,5-三(5,5-二甲基-1,3-二氧杂环己内磷酸酯基)苯(FR)和聚磷酸铵(APP)组成的膨胀阻燃剂(IFR)与低密度聚乙烯(LDPE)作用,制备出新型膨胀阻燃低密度聚乙烯复合材料(IFR/LDPE)。用差示扫描量热法(DSC)研究IFR对LDPE非等温结晶行为的影响,用Jeziorny法、Ozawa法及莫志深法研究了低密度聚乙烯阻燃改性前后的非等温结晶动力学,并用Kissinger法、Takhor法研究了纯LDPE及IFR/LDPE共混体系结晶活化能的变化。结果表明:IFR的加入在提高LDPE阻燃性能的同时,对LDPE结晶起到异相成核作用,但是阻碍了PE分子链的规则排列,使LDPE晶体的生长减慢,最终使阻燃聚乙烯总的结晶速率降低。     

不同增容剂对POE增韧聚乳酸性能的影响

用双螺杆挤出机制备了聚乳酸(PLA)、聚烯烃弹性体(POE)和4种不同增容剂(马来酸酐接枝POE、马来酸酐、丙烯酸酯双官能化POE、丙烯酸酯与缩水甘油酯双官能化的POE、甲基丙烯酸缩水甘油酯接枝POE)的共混物,考察了不同增容剂对共混物力学性能和断面形貌的影响,分析了退火前后共混物力学性能的变化。结果表明,在使用自制的甲基丙烯酸缩水甘油酯接枝POE(POE-g-GMA)作为增容剂,三元体系PLA/POE/POE-g-GMA的质量比为80/15/5时,复合材料力学性能达到最佳,此时缺口冲击强度为12.3 kJ/m2,是纯PLA的3.7倍,拉伸强度为47.5 MPa。     

相容剂对聚丙烯/聚乙醇酸共混物结构与性能的影响

采用熔融共混法制备了聚丙烯/聚乙醇酸共混物(PP/PGA),研究了相容剂聚丙烯接枝马来酸酐(PP-gMAH)用量对共混物力学性能、熔融结晶行为、流变行为和断面形貌的影响。结果表明:PP-g-MAH的加入能明显改善共混体系的相容性,共混物的力学性能得到提升。PP-g-MAH对PGA结晶具有异相成核作用,且先结晶的PGA又可作为PP结晶的异相成核剂。随相容剂用量增大,PGA结晶温度升高,结晶完善程度降低,甚至不结晶,PP的结晶温度先降低后升高,且复数黏度呈先增大后减小的趋势。     

Surlyn和HDPE共混增强LDPE的微结构及性能比较

为了改善低密度聚乙烯(LDPE)的综合性能,用离子聚合物Surlyn和高密度聚乙烯(HDPE)分别对LDPE进行共混改性,着重研究了改性聚合物的质量分数对LDPE共混体系的微观结构、力学性能以及热性能的影响规律。结果表明,HDPE与LDPE之间具有良好的界面相容性,而Surlyn则呈类球形细小粒子在基体中弥散分布,且其粒径随着Surlyn添加量的增加而增大。虽然Surlyn能全面提升LDPE的力学性能,但其对抗拉强度和弹性模量的提升幅度要远远低于HDPE。示差扫描量热仪(DSC)测试佐证了LDPE与HDPE的部分相容,但Surlyn对LDPE相的熔融和结晶行为影响甚微。Surlyn的引入没有改变LDPE相的热分解过程,但导致了共混体系热分解温度的下降;HDPE则使共混体系的热重曲线(TGA)在高温区右移,共混体系的热分解过程为二阶失重形式。     

Microstructural,thermal and rheological correlations to mechanical response of polyamide-6(glass filled)/polyetherimide blend: effect of ethylene-octene copolymer on toughening of blend

Melt mixed glass-filled polyamide 6(PA6)/polyetherimide (PEI) blends were prepared in a co-rotating twin screw extruder over the entire composition range of 0–100 wt% of polyamide 6. These blends were characterized by structural, rheological, mechanical and thermal properties. Crystallization behavior and phase morphology of the blends were also investigated. The blend with the composition PA6/PEI 75/25 showed overall improved mechanical properties along with low resultant viscosity which can be processed on standard equipment. Shear viscosity along with shear stress of the blends were analyzed using shear rheometer which concluded that the blends can be processed on standard equipment due to resultant low viscosity. Scanning electron microscope micrographs revealed that the morphology of the blends showed a two phase structure in which the minor phase was dispersed as domains in the continuous phase. Polyolefin elastomer (POE) as impact modifier was added to the above composition in the range of 0–15 phr to study its effect. The thermal characteristics of PA6, PEI, and PA6/PEI blends with and without POE were investigated using DSC and TGA which revealed that the melting temperature and crystallization temperature of the blend remained unchanged while XRD results showed percent crystallinity was increased slightly. Furthermore, it can be said that the blend with composition PA6/PEI 75/25 with 10 phr impact modifier loading was suitable for high end applications because it combines the high mechanical properties of glass-filled PA6 with inherent flame-retardant property of PEI while POE overcomes the physical weakness of moisture absorption.     

相容性对PA66/POE共混材料形态、微结构及力学性能的影响

采用SEM、TEM、DSC及材料力学性能实验方法研究了马来酸酐 ( MAH ) 接枝乙烯-辛烯共聚物弹性体 ( POE ) 对PA66/POE共混材料形态、微结构及力学性能的影响。结果表明:热引发官能化POE产物 ( POE-g-MAH ) 可显著改善PA66/POE共混材料的相容性,使材料分散相尺寸减小,分布均匀,且材料缺口冲击强度显著增大。实验发现,PA66/POE-g-MAH共混材料分散相的弹性体颗粒内部存在较多份量的有序结构,材料中的分散相颗粒具有明显促进结晶的作用,此作用引起PA66基体结晶温度增加,结晶度增大,并在分散相质量分数为15% 的脆韧转变条件下,达到极大值。试样熔体的冷却速率越快,则此种促进结晶的作用就越明显。      

Effect of the processing method on the mechanical properties and morphology of compatibilized PA6/LDPE blends

In this work, the effect of the processing method on the mechanical properties and morphology of compatibilized PA6/LDPE blends was investigated. The blends were prepared by two processing methods: Injection and Extrusion followed by Injection. The compatibilizers used were polyethylene grafted with acrylic acid (PEgAA) and polyethylene grafted with maleic anhydride (PEgMA). The results showed that in both processing methods the impact strength and elongation at break of the compatibilized blends were greater than those of the uncompatibilized ones. For the blends prepared by injection, the impact strength of PA6/PEgMA/LDPE blend was greater than that of PA6/PEgAA/LDPE blend. For the blends prepared by extrusion followed by injection, the impact strength of the PA6/PEgAA/LDPE blend was greater than that of PA6/PEgMA/LDPE blend. SEM analysis showed that the morphology of the PA6/PEgAA/LDPE blend prepared by extrusion followed by injection was more stable than that of the same blend prepared only by injection.     

Blends of PP/PE co‐octene for modified atmosphere packaging applications

The aim of this work was to obtain films of polypropylene (PP)/polyethylene co‐octene (POE) blends and study the influence of their composition and mixing conditions on final morphology and ultimate properties (thermal, mechanical, oxygen and water vapour transmission rates). Scanning electron microscopy showed segregation of POE domains in the PP matrix. Thermal analysis indicated that the addition of POE modified neither the melting temperature nor the crystallinity of PP in the pressed films. It was found that permeabilities of films were mainly related to POE content rather than morphological features. For the maximum POE concentration used (40%), the oxygen permeability increased up to ∼100% from that of neat PP. A similar trend was found for water vapour permeability. Rigidity of blends dropped significantly with the addition of POE although their ductility slightly increased when compared to pure PP. No significant effect of blend preparation conditions on these properties was found. Mechanical and permeability characteristics of films make them very attractive to be used for MAP of fresh produce such as apple, blueberry and mushroom. Copyright © 2011 John Wiley & Sons, Ltd.     

Mechanical and thermal properties of compatibilized composites of polyethylene and esterified lignin

Lignin have been esterified using phthalic anhydride and then blended with (up to 40 wt.%) low density polyethylene (LDPE). Maleic anhydride grafted LDPE has been added as compatibilizer. The mechanical and thermal properties of the blends were measured according to ASTM standards and compared with those of neat LDPE. The results reveal that addition of compatibilizer improved the mechanical properties significantly approaching values close to those of neat LDPE. The scanning electron micrographs of the blend specimens also support the above observations. Thermogravimetric analysis showed greater thermal stability for the compatibilized blends. The char content has been found to increase with increasing filler (lignin phthalate) content. DSC analysis revealed that the crystallinity values of the blends slightly increase by the addition of filler (lignin phthalate).     

LLDPE及LLDPE／LDPE在不同条件下的结晶行为

ＤＳＣ的研究表明ＬＬＤＰＥ高分子量线形分子结晶时，短支化链的链节不参与共晶。当ＬＬＤＰＥ／ＬＤＰＥ共混物淬冷或快速结晶时，ＬＬＤＰＥ中的线形分子可与ＬＤＰＥ中长支化链的链节产生共晶，其熔融单峰较宽，峰位随ＬＬＤＰＥ含量增加而稍向高温移动。     

Studies on microcellular soles based on natural rubber/polyethylene blends

Microcellular (MC) soles based on NR/polyethylene blends were developed as possible replacements for the conventional NR/HSR soles. The mechanical properties of the soles suggest that 80/20 NR/LDPE blends can be used for light weight good quality soles. 80/20 blends of NR/HDPE are also found to be promising base materials for good quality soles. A part of HSR in a NR/HSR blend was replaced by LDPE and the effect of replacement on the mechanical properties was evaluated. It is found that 70/15/15 NR/HSR/LDPE and 60/20/20 NR/HSR/LDPE based MC soles show better mechanical properties than NR/LDPE based MC soles.     

Characterisation of the thickness of transition layer and its relation to mechanical properties of polypropylene/poly(ethylene-co-octene) blends

Poly(ethylene-co-octene) (POE) was mixed into polypropylene (PP) by an internal mixer, which was installed on on-line small-angle laser light scattering (SALLS) device. A new parameter called the thickness (d) of transition layer was introduced to describe the compatibility of PP/POE blends in both dynamic and static states. Using the correlation distance, a_c (it was indicative of the dimension of the dispersed phase pellets), d was calculated for the PP/POE blends based on the SALLS theory. The results indicated that the average values of d increased with increasing concentration of dispersed phase and had a maximum value at 40/60(PP/POE) for the blends. And the values of d showed much more violent fluctuation and were much larger at the early stage of mixing, but at a later stage d leveled off and approached to steady state. In addition, the relationships between the thickness of transition layer and mechanical properties were studied. It showed that the notched Izod impact strength and the average values of d of PP/POE blends increased with increasing of POE concentration, while the Young's modulus and flexural modulus decreased. The results indicated that SALLS method was an effective method to deal with diffuse transition layer of PP/POE blends and d was indeed a valid parameter to describe compatibility.     

Investigation of the effect of addition of calcium stearate on the properties of low-density polyethylene/poly(ε-caprolactone) blends

Low-density polyethylene (LDPE) was blended with poly(ε-caprolactone) (PCL), prepared in proportions of 75/25, 50/50, and 25/75 (LDPE/PCL, wt/wt%). The effect of the addition of calcium stearate (CaSt) of these polymers was assessed by melting flow index, differential scanning calorimetry, tensile test, scanning electron microscopy (SEM), biodegradation in simulated soil with calcium determination, and enzymatic degradation. The addition of CaSt reduced the MFI of the PCL and of the 75/25 blend. The incorporation of 25 % of PCL slightly increased the T _m of LDPE. The tensile strength had no significant changes with the addition of CaSt and the polymers showed that they are incompatible according to this property. SEM showed poor interfacial interaction between PCL and LDPE, as well as that they are immiscible, and showed no significant changes on the morphology of the materials with the addition of CaSt. The results show that polymer samples after biodegradation in simulated soil present more calcium content than initial samples polymer. The soil analysis shows that the soil that contains the polymers submitted to thermal aging show smaller calcium content than the samples that were not aged. Lipase enzyme reinforced its specificity over PCL, and the addition of CaSt reduced the degradation of PCL and the 75/25 PCL/LDPE blend, however, it increased the rate of degradation of 50/50 and 25/75 blends.