Fracture behaviors of metallocene‐catalyzed polyethylene elastomer via silane crosslinking

Silane moisture‐cured metallocene‐catalyzed polyethylene (mPE) to form an elastomer has been prepared. Metallocene polyethylenes with two different levels of comonomer contents were grafted with various amounts of vinyltriethoxy silane. “Threshold” fracture energy is roughly proportional to the reciprocal square root of Young's modulus. By relating tensile strength to tear strength, the corrected average depth of flaw is in the range of 40.5 ± 11.0 μm, which successfully confirms the extension of conventional elastomeric theory to the low crystalline vulcanizates under some limitations. The cutting strength of mPE vulcanizates gives an intermediate value when compared with crystalline plastics and conventional elastomer, and is comparable with other evaluations of cutting strength for different types of materials, which further signifies the importance of crystalline yielding even in the nano‐fracture zone of deformation. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2472–2481, 2006     

POE和mPE增韧木塑复合材料的研究

采用废木粉填充高密度聚乙烯制备木塑复合材料,采用茂金属聚乙烯(mPE)和乙烯-辛烯共聚物(POE)对复合材料进行增韧,并阐述了它们的增韧机理,讨论了增韧剂用量对复合材料的力学性能如拉伸强度、弯曲强度、弯曲模量、冲击强度和硬度的影响,综合评价了两种冲击改性剂的增韧效果。研究结果表明:两者对高密度聚乙烯基木塑复合材料均有良好的增韧效果。单就增韧效果而言,POE优于mPE,但在其他性能如拉伸强度、弯曲强度、弯曲模量、硬度以及耐热性等方面,mPE明显优于POE。     

Mechanical properties and morphologies of PP/mPE/filler composites

Because of the poor impact behavior of polypropylene (PP) at low temperatures, the blending of PP with metallocene‐polymerized polyethylene (mPE) elastomers was investigated in this study. However, a reduced modulus of the overall blend was inevitable because of the addition to elastomers. To obtain a balance of the properties, we introduced rigid inorganic fillers to PP/mPE blends. The performance of the composites was characterized with tensile and Charpy notched impact tests, and the fracture morphology was examined with scanning electron microscopy. The results showed that the effects of fillers in a brittle matrix and in a ductile matrix were quantitatively different. For PP/mPE/filler ternary composites, the dependence of Young's modulus and yield strength on CaCO₃ content was not significant compared with that of PP/filler binary composites, whereas the elongation at break and tensile toughness at room temperature for PP/mPE/filler systems were more improved. The impact strength of the PP/mPE blends filled with untreated glass beads and CaCO₃ at a low temperature was lowered because of the weak interfacial bond. However, the values of the impact strength of the PP/mPE/filler composites at a low temperature remained at a high level compared with that of pure PP. In particular, a PP/mPE blend filled with surface‐treated kaolin had a higher low‐temperature impact toughness than the unfilled blend. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 3029–3035, 2002; DOI 10.1002/app.2333     

mPE/LDPE交联物在聚丙烯管材专用料中的增韧作用研究

流变研究发现,mPE/LDPE交联物具有多分散性的蜂窝状网络结构,并呈现类弹性体特征.在嵌段共聚聚丙烯的增容下,可以显著提高均聚聚丙烯的冲击韧性,且其耐高温蠕变性能也优于几种典型的聚丙烯管材专用料.     

茂金属聚乙烯的淋洗分级分析

采用升温淋洗分级技术将国产茂金属催化剂制备的茂金属聚乙烯树脂分级,对分部分级样品进行核磁共振碳谱,差示扫描量热和凝参透色谱测试,发现分级样品结晶度分布窄吱链含量对热性能的影响很大,在多分散性上表现为高分子量链上的支链含量低。     

Studies on the rheological,phase morphologic,thermal and mechanical properties of poly(trimethylene terephthalate)/ethylene propylene diene monomer copolymer grafted with maleic anhydride/metallocene polyethylene blends

The rheological, phase morphologic, thermal and mechanical properties of poly (trimethylene terephthalate)/metallocene polyethylene (PTT/mPE) blends in the presence of ethylene propylene diene monomer copolymer grafted with maleic anhydride (EPDM-g-MAH) as compatibilizer are studied by means of a capillary rheometer, scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and thermogravimetric analyzer (TGA). Results suggest that the compatibility of PTT/mPE blends is improved greatly after the addition of a compatibilizer. The radius of the dispersed phase in the system decreases greatly when the compatibilizer is added into the blend. When the amount of compatibilizer exceeds 8 wt-%, the size of dispersed phase becomes larger again. This phenomena could be attributed to the higher viscosity of the EPDM-g-MAH phase, which is dispersed more difficulty in the PTT phase of lower viscosity, thus the mixing efficiency is apparently decreased during the melt blending process. Moreover, the melt viscosity of the blend reaches the maximal value in case of 4 wt-% compatibilizer content, above which it would decrease again. This result is associated with the generation of more and bigger dispersed phase inside the bulk phase, thus the grafting efficiency at the interface is decreased, which could result in lower viscosity. The DSC results suggest that the mPE component shows a nucleating effect, and could increase the overall degree and rate of PTT crystallization, while the addition of a compatibilizer might slightly diminish these effects. In addition, the blend with 4 wt-% compatibilizer shows the best thermal stability. Furthermore, the Izod impact strength and the tensile strength at room temperature of the blend are also markedly improved by the addition of a 4–8 wt-% compatibilizer.     

POE/mPE/PE-HD改性PE-LD热封薄膜性能研究

采用热塑性弹性体乙烯辛烯共聚物(POE)改善低密度聚乙烯(PE-LD)薄膜的热封性能和拉伸强度,使用茂金属线形低密度聚乙烯(mPE)提高PE薄膜的热封强度,使用高密度聚乙烯(PE-HD)对PE-LD改性,提高其拉伸强度。结果表明,与未改性的PE薄膜相比,在外层为PE-LD、中层为PE-LLD(7042)∶PE-HD=70∶30、内层PE-LLD(7050)∶PE-LD∶POE(9361)∶mPE(M4707EP)=10∶80∶5∶5时,其纵、横向拉伸强度和热封强度分别提高了2973、1721 MPa和1611 N/15 mm。     

PTT/EPDM-g-MAH/mPE共混体系的相形态与流变行为

研究了聚对苯二甲酸丙二酯/马来酸酐接枝三元乙丙橡胶/茂金属聚乙烯共混体系(PTT/EPDM-g-MAH/mPE)的相形态和流变行为。结果表明,增容剂EPDM-g-MAH可以明显改善PTT与mPE的相容性,但含量超过4%时分散相的数目增加、尺寸增大。PTT/EPDM-g-MAH/mPE共混物熔体为假塑性流体,表观黏度随剪切速率的增加而降低;当EPDM-g-MAH的含量在0%~16%范围内时,共混物的非牛顿指数先减小后增加再减小;表观黏度、粘流活化能先增加后减小,并在4%时出现极值。     

Effects of dispersed phase composition on thermoplastic polyolefins

Ternary blends of polypropylene (PP), ethylene–octene copolymer (mPE), and high‐density polyethylene (HDPE) were prepared based on the phase behavior and physical properties of mPE/HDPE binary blends, and the results were interpreted in terms of morphology and both rheological and mechanical properties of the ternary blends as well as the binary blends. It was found that when mPE encapsulates HDPE in the PP matrix, compared to the encapsulation of mPE by HDPE, better blend properties were obtained, presumably because of the compatibilizing effect of mPE between PP and HDPE. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 179–188, 2004     

茂金属聚乙烯交联反应挤出流动模型分析

在研究茂金属聚乙烯在双螺杆挤出机中进行的复合交联反应挤出过程流动模型时,在三参数关联流动模型中引入了第4个参数,获得了更好的停留时间分布曲线拟合效果。但是,其物理意义难以确定。为此,根据双螺杆挤出机的结构特点提出了RDBFC模型,获得了较好的拟合效果,物理意义更加合理。