【作者】 丁正亚；

【导师】 胡国胜；

【作者基本信息】 中北大学 ， 材料学， 2008， 硕士

【摘要】 尼龙11（PA11）树脂主要应用于汽车输油管道和煤气工程等方面，随着环保要求的日趋提高，单一的PA11树脂的阻隔性能已不能完全达到行业标准。为了提高其阻隔性能，本课题采用目前阻隔性能最好的乙烯-乙烯醇共聚物（EVOH）与PA 11通过熔融共混法制备出了PA11/EVOH阻隔材料，采用扫描电子显微镜（SEM）、毛细管流变仪、X射线衍射（WAXD）、差示扫描量热仪（DSC）和偏光显微镜（POM）等对PA11/EVOH阻隔材料的力学性能、阻隔性能、凝胶含量、形态结构、流变性能和结晶性能等方面进行了研究。力学性能和阻隔性能研究结果表明，当阻隔材料的配比为PA11/EVOH/DCP=80/20/1.5时，材料的吸油值达到最小值为0.244%(二甲苯)，冲击性能达到最大值5.31KJ/m2，此时的拉伸强度为53.5MPa。与纯PA11相比，共混材料的阻隔性能、冲击强度和拉伸强度分别提高了5倍、18%和17.4%。SEM照片表明，此时EVOH以交叠的不连续性片层状结构分散于PA11基体树脂中，这对阻隔性能的提高起到了关键作用。凝胶含量研究结果表明PA11/EVOH阻隔材料的凝胶含量随着DCP含量的增加先升高后降低，在DCP含量为1.5%时达到最大值；同时，EVOH/DCP体系低凝胶含量表明EVOH发生自交联的几率较小，主要是PA11和EVOH之间发生共交联反应。结合FT-IR分析，提出了DCP存在下，PA11和EVOH发生共交联的机理。考察了DCP含量对PA11/EVOH阻隔材料流变行为的影响。研究结果表明PA11/EVOH阻隔材料为假塑性流体，表现出切力变稀的现象。与未添加DCP的相比，加入DCP后体系的非牛顿指数n值变小，说明加入DCP后体系对剪切速率的敏感性降低；在给定剪切应力和剪切速率下，体系的表观粘度随着DCP含量的增加先升高后降低，在DCP含量为1.5%时达到最大值，这与凝胶含量的测试结果是一致的；体系的粘流活化能随着DCP含量的增加整体上呈现下降趋势，对温度的敏感性下降。采用DSC研究了PA11/EVOH/DCP共混物的结晶动力学。等温结晶动力学研究结果表明：Avrami方程很好的描述了PA11/EVOH/DCP共混物的等温结晶行为。EVOH和DCP的加入产生的交联部分起到了异相成核的作用，提高了PA11的结晶速率；DCP的加入改变了PA11/EVOH阻隔材料的晶体生长方式和成核机理。根据Hoffman-Weeks理论计算，PA11/EVOH/DCP共混物的平衡熔点比PA11的低，说明EVOH和DCP的加入降低了PA11的结晶完善程度。非等温结晶研究结果表明：Ozawa理论不适用描述PA11/EVOH/DCP共混物的非等温结晶过程，而修正的Avrami方程和Mo法能很好的处理此过程。EVOH和DCP的加入阻碍了晶体的生长，降低了结晶生长速率，同时也改变了PA11的成核和晶体生长规律。更多还原

【Abstract】 Polyamide 11(PA11) was mostly used as automobile pipe-laying and municipal gas pipeas well as offshore oilfield application. With the more strict controls on the environmentalrequirements, the barrier properties of neat PA11 can not meet with the industry standards. Inorder to improve its barrier properties, PA11/EVOH composites were pr epared by meltingcompounding, and their mechanical properties, barrier properties, gel content, morphologystructure, rheological behavior and crystallization properties were investigated by scanningelectron microscopy (SEM), capillary rheometer, X -ray diffraction (WAXD), differentialscanning calorimeter (DSC) , polarizing microscopy (POM) and capillary rheometer ,respectively.The experimental results of mechanical properties and barrier properties showed that theoil-absorption reached the minimum value (0.244%, xylene), impact strength and tensilestrength was increased up to 5.31KJ/m2 and 53.54MPa in the case ofPA11/EVOH/DCP=80/20/1.5. In comparison with that of the neat PA11, the barrier property ,impact strength and tensile strength of the PA11/EVOH/DCP composi tes were increased by500%, 18% and 17.6%, respectively . SEM micrographs showed that the EVOH was dispersedwithin PA 11 matrix in the form of discontinuous mutual crossover laminar structure, whichwere contributed to the improvement of the barrier property.It was found that the gel content of PA11/EVOH composites initially increased and thenreduced with the increasing loading of the DCP, and reached its maximum at the level of1.5% DCP content. furthermore, the variation of gel content of EVOH/DCP system togetherwith FT-IR results indicated that the co-crosslinking between EVOH and PA 11 predominatedover the self-crosslinking of EVOH.The effect of DCP content on the rheological behavior of PA11/EVOH blends wasinvestigated. The results showed that all PA11/EVOH blends with or without DCP were pseudo-plasitc and exhibited shear-thinning. The non-Newtonian indexes (n) decreased withthe addition of DCP, which indicated that the sensitivity of composite to shear rate decreased.In the case of constant shear stress and shear rate, the apparent viscosity decreased initiallyand then after increased with the increasing DCP content , and displayed a maximum value atthe level of 1.5% DCP content. The reduced apparent viscous activation energy of compositeswith the increasing DCP content indicated that the addition of DCP decreased thetemperature-sensitivity.The crystallization kinetics of PA11/EVOH/DCP composites was investigated by DSC.The studies on the isothermal crystallization showed that Avrami equation well describedthe isothermal crystallization of PA11 and its composites, the co-crosslinked domains formedafter the addition of EVOH and DCP might act as the heterogeneous nucleating agent andthus increased the crystallization rate of PA11; The mechanism of crystallization nucleationand growth of PA11/EVOH composites was also changed by the addition of DCP. Theequilibrium melting point of PA11/EVOH composites obtained by the Hoffman -Weekstheory was lower than that of neat PA11, which indicated that the addition of EVOH and DCPdecreased the perfect of crystallization.The analysis of non-isothermal crystallization showed that Ozawa equation was notsuitable to describe the non-isothermal crystallization process of PA11 and its composites,while the modified Avrami and Mo equation took great advantages over treating thenon-isothermal crystallization kinetics. The addition of EVOH and DCP impeded the growthof crystals, reduced the crystal growth, and changed the crys tallization nucleation and thegrowth of crystals.更多还原