【作者】 何三雄；

【导师】 吴唯；

【作者基本信息】 华东理工大学 ， 材料科学与工程， 2011， 博士

【摘要】 针对尼龙6(PA6)具有缺口冲击敏感性和低温及干态下冲击强度低等缺点,本论文对其进行增韧改性研究。选用了热塑性弹性体苯乙烯-乙烯-丁二烯-苯乙烯嵌段共聚物(SEBS),并将其分别与甲基丙烯酸缩水甘油酯(GMA)和马来酸酐(MAH)进行接枝,得到2种官能化接枝物SEBS-g-GMA和SEBS-g-MAH。然后,用官能化SEBS.以及官能化SEBS与聚碳酸酯(PC)协同对PA6进行增韧,同时以纳米有机蒙脱土(OMMT)为填料对PA6进行补强, GMA或环氧树脂(EP)为相容剂,制备了综合性能优异的高韧性工程塑料。采用XRD、SEM、TGA、DSC、FTIR、Molau实验、力学性能测试以及流变性能测试等多种测试手段,研究了官能化基团种类及接枝率、填料和相容剂的用量、以及各组分间的微交联反应体系对纳米复合材料形态、结构和性能的影响。首先将PA6与国内工业化生产的OMMT进行熔融共混,制备了PA6/OMMT纳米复合材料。通过力学性能测试发现,当OMMT含量为4wt%时,复合材料具有较高的强度和弯曲模量,但冲击强度较纯PA6有所降低。对复合材料进行小角X射线衍射扫描以及透射电镜观察,发现OMMT已经被PA6剥离,较均匀地分散在基体中。Molau实验结果表明OMMT以胶体形式均匀地分散在甲酸溶液中,不沉降、不分相。分别以GMA和MAH为功能单体,熔融挤出制备了官能化弹性体SEBS-g-GMA和SEBS-g-MAH,用滴定分析测定了两种接枝物的接枝率,分别为2.39%和1.2%。再分别以SEBS-g-GMA和SEBS-MAH为增韧剂、OMMT为填料,制备了尼龙6/弹性体／蒙脱土三元纳米复合材料。研究了三元纳米复合材料的力学性能、结晶性能和热稳定性以及分散相在基体中的分散状态。结果表明,三元纳米复合材料的性能介于尼龙6、尼龙6/弹性体之间,弹性体使得PA6/OMMT纳米复合材料的冲击强度提高。当弹性体含量达到约30%时,三元纳米复合材料发生脆-韧转变,在进行缺口冲击强度测试时试样已经不能完全断裂,冲击韧性大幅提高。同时复合材料的强度仍保持在纯PA6的90%以上,材料的硬度与韧性达到较好地平衡。将SEBS-g-GMA和SEBS-g-MAH对PA6复合材料的增韧效果作比较后发现,不同的接枝物导致了分散相在基体中有不同的分散状态。在组成、加工条件相同情况下,共混体系中SEBS-g-GMA的粒径远大于SEBS-g-MAH的粒径,其增韧的效果要差。少量的OMMT使得分散相粒子尺寸减小；较多量的OMMT能阻碍弹性体与PA6基体间的界面黏结,导致粒子尺寸增大,降低了材料的冲击性能。用SEBS-g-GMA增韧制备的PA6/SEBS-g-GMA及PA6/S EBS-g-GMA/OMMT复合材料,均不能溶解于甲酸中,试样颗粒悬浮在甲酸溶液的最上方；而SEBS-g-MAH增韧制备的PA6/SEBS-g-MAH及PA6/SEBS-g-MAH/OMMT复合材料可溶于甲酸,显示的为一牛奶状的悬浮物。用3种不同接枝率的SEBS-g-MAH增韧制备的PA6/SEBS-g-MAH/OMMT复合材料中,随着MAH接枝率的增大,分散相的粒径减小,但复合材料的冲击强度基本保持不变、与MAH的接枝率大小无关.SEBS一g-GMA和SEBS-g-MAH均降低了PA6的熔融温度并且对PA6的结晶有阻碍作用。通过两步共混加工,即先将PA6与OMMT共混后,再将挤出物与SEBS-g-MAH共混制备的三元纳米复合材料具有优异力学性能,其冲击强度比用一步加工法(即,共混组分混合后同时加入到挤出机中进行挤出)制备的复合材料的冲击强度高122%。一步共混加工时,另加入少量GMA或EP作为相容剂,所制备的纳米复合材料与两步加工制备的具有相近的力学性能,并且极大地提高了材料的断裂仲长率,得到一种高韧性的工程塑料。相容剂的加入,使得共混体系间产生了微交联反应,共混物不能完全溶解于甲酸溶液中,复合材料体系的黏度增大,提高了材料的储能模量和损耗模量。采用弹性体SEBS-g-MAH与PC复合增韧PA6,极大地提高了材料的冲击强度;同时用EP改善PC与基体PA6间的相容性,经反应挤出制备了高韧性的新型PA6工程塑料,当EP含量为1wt%时,冲击强度达到55.61kJ/m2,断裂伸长率达到306.4%,比纯PA的分别提高了313.2%和625.2%。这种新型增韧合金具有非常出色的机械性能,蒙脱土的引入进一步提高了复合材料的拉伸和弯曲性能。随着EP用量的增加,PA6与PC的相界面变的更加模糊,复合物的拉伸强度、弯曲强度及模量逐渐增大,冲击强度先增大后略下降。PC的加入有助于提高PA6/SEBS-g-MAH共混物的耐热性,相容剂EP使得体系中各相之间的界面黏结作用增强,进一步提高了材料的热分解温度。更多还原

【Abstract】 The aim of this work is to toughen polyamide 6 (PA6) because notch sensitivity and brittleness in low temperature limit its application. A styrene-ethylene/butadiene-styrene triblock copolymers (SEBS) was functionalized respectively with glycidyl methacrylate (GMA) and maleic anhydride (MAH). PA6-based composites were prepared using the functionalized SEBS as a toughener, or adding polycarbonate at the same time, and one commercial organo-montmorillonite (OMMT) served as reinforcing filler. GMA or epoxy resin (EP) was used as a compatibilizer for the composites. Influence of the type of functional group, grafting degree, the contents of the filler and compatibilizer, and the micro-crosslinking among the components on the morphology, the structure and properties were investigated by all kinds of methods, e.g. XRD, SEM, TGA, DSC, FTIR, Molau test, mechanical properties test and rheology.Firstly, PA6/OMMT nanocomposites were prepared by means of melt blending. When the content of OMMT was 4wt%, the nanocomposite has a higher tensile strength, flexile strength and flexile modulus. But the impact strength was decreased. The exfoliated behavior was confirmed by XRD and TEM. PA6/OMMT blend could scatter uniformly in the formic acid solution without sedimentation and phase separation.The SEBS-g-GMA and SEBS-g-MAH were respectively prepared using GMA and MAH though melt extrusion. The grafting degrees were respectively 2.39% and 1.2%, which were decided by titration. SEBS-g-GMA and SEBS-g-MAH were used to prepare PA6/elastomer/OMMT nanocomposites. The mechanical properties, crystallization behavior, thermal stability and the morphology were investigated. The PA6/elastomer/OMMT had mechanical properties balanced between those of PA6 and PA6/elastomer blends. Brittle-ductile transition could happen when the content of elastomer was 30wt%, and the toughness improved rapidly. The tensile strength and flexile strength are above 90% of pure PA6. There is a clear trade-off between stiffness/strength versus toughness/ductility.SEBS-g-GMA and SEBS-g-MAH had the different morphology in the composites. The particle size of SEBS-g-GMA is much larger than that of SEBS-g-MAH. The toughening efficiency of SEBS-g-GMA was much lower than SEBS-g-MAH. The elastomer particle size decreased at low OMMT loading. With increasing the content of OMMT, OMMT weakened the interfacial adhesion between PA6 and functionalized elastomer leading to an increase in the elastomer particle size and a decrease in the impact strength of the composites. PA6-based composites toughened by SEBS-g-GMAdid not dissolve in the formic acid, and suspended in the upper of the tube. A milky and colloidal suspension was observed for PA6-based composites toughened by SEBS-g-MAH. The elastomer particle size clearly decreased with increasing MAH content. The impact strength remained almost constantly. SEBS-g-GMA and SEBS-g-MAH both decreased the melt temperature, and hindered the crystallization of the composites.The ternary composites were prepared by two different blending sequences (N1 and N2). The method N1 means PA6, elastomer, and OMMT were blended simultaneously. The method N2 means that the ternary composite was produced through the premixing of PA6 and OMMT first and then melt blending with elastomer. The composite (N2) has better mechanical properties. The notched impact strength of the one composite (N2) was 122% higher than that of the other composite (N1), even for the same formulation. For the ternary composites prepared via method Nl with the addition of GMA or EP, the tensile strength, flexural strength, and flexural modulus just slightly decreased, whereas the impact strength and elongation at break were significantly enhanced. The chemical reaction between PA6, SEBS-g-MAH, and the compatilizer could enhance the viscosity, storage modulus, and loss modulus. The blends couldn’t dissolve in formic acid solution.The impact strength of PA6/SEBS-g-MAH/PC composite improved greatly compared with that of PA6/SEBS-g-MAH composite. Epoxy resin was used to improve the compatibility between PA6 and PC. Then adding EP (1wt%) to PA6/SEBS-g-MAH/PC alloy, the notched impact strength of alloy is 55.61kJ/m2 (increasing 313.2% as that of pure PA6) and the elongation at break is 306.4%(increasing 625.2% as that of pure PA6). Novel toughening alloy is gained with outstanding mechanical properties. In addition, the adding of OMMT improved the tensile and flexile properties of the composite remarkably. The interphase boundaries became increasingly indistinctive with the adding of EP, and the tensile and flexile strength increased. The notched impact strength increased firstly and then decreased. Polycarbonate would improve the thermal stability of the composites. The thermo-decomposing temperature rises obviously due to the crosslinking caused by the compatilizer EP.更多还原