论文标题:尼龙6/高密度聚乙烯/黏土复合材料结构性能研究
Structure and Properties of Polyamide 6/High Density Polyethylene/Clay Composites
论文作者
论文导师 方征平,论文学位 博士,论文专业 高分子化学与物理
论文单位 浙江大学,点击次数 15,论文页数 147页File Size14886K
2007-01-24论文免费下载 http://paper.dic123.com/lunwen_406509782/
本文工作主要分成两部分：第一部分是高密度聚乙烯(HDPE)／黏土(Clay)和尼龙6(PA6)／Clay纳米复合材料的研究；第二部分是Clay对PA6／HDPE和PA6／高密度聚乙烯接枝丙烯酸(PEAA)共混体系增容作用研究。 1．HDPE／Clay和PA6／Clay纳米复合材料的研究 用熔融共混的方法制备了HDPE／Clay和PEAA／Clay纳米复合材料。采用正电子湮没技术(PALS)测试了自由体积的尺寸及浓度，研究了自由体积性能与拉伸模量之间的关系。结果表明：Clay在PEAA中有较好的分散，与基体形成较多的界面层，使自由体积强度(I_3)增加，且界面效应使复合材料的模量提高，而在HDPE体系中，发生团聚，模量下降。 用熔融共混的方法制备了PA6／Clay纳米复合材料，采用XRD、SEM、TEM和DSC等实验手段对材料的结构和性能进行了表征。研究结果表明：Clay在PA6中有较好的剥离和分散。在低剪切速率下，Clay的加入降低了PA6的表观粘度，而当剪切速率大于3000s~(-1)时，加有Clay的PA6表观粘度稍高于纯PA6，而且在Clay加1～4 phr之间时，Clay的量对体系的粘度影响比较小。Clay在PA6中较好的剥离和分散，并且和PA6有较好的相互作用，在一定程度上阻碍了其链段运动，PA6的结晶温度随Clay量的增加而降低。 2．Clay对PA6／HDPE和PA6／PEAA共混体系增容作用的研究 用熔融共混的方法制备了PA6／HDPE／Clay和PA6／PEAA／Clay纳米复合材料，研究了Clay对PA6／HDPE和PA6／PEAA体系相容性的影响。 对PA6／HDPE体系，从四个角度来分析Clay的增容作用：(1)Clay含量的变化。研究表明随Clay量的增加，分散相HDPE尺寸明显减小。XRD和TEM结果表明大部分的Clay已经剥离，并比较均匀地分散在PA6相或PA6和HDPE的界面周围。随着Clay含量的增加，插层的Clay也增加，Clay在界面上聚集增加，HDPE相被拉长而变形，界面层厚度有一定增加，界面变模糊。(2)加工工艺的变化。转速对相形态的影响：对于PA6／HDPE共混物，40rpm时分散相HDPE直径变得最小，继续增加转速，HDPE相尺寸有变大的趋势，相不是很稳定，而在加入4 phr Clay后，当转速大于等于40 rpm后相基本稳定。时间对相形态的影响：对于PA6／HDPE共混物，随着共混时间的增加，HDPE相尺寸逐渐变小。当体系中加入1phr Clay后，相尺寸要小于不加Clay的体系，但随共混时间延长，HDPE相尺寸还是会逐渐变小。加入较多Clay后，随时间的变化，HDPE相尺寸进一步变小，而且最后相趋于稳定。(3)PA6／HDPE共混物组成的变化。结果表明不加Clay时，PA6为主相的体系中，HDPE相尺寸要大于相应的HDPE为主相的PA6的相，添加2 phr Clay后，分散相尺寸都变小，而且PA6为主相的体系，影响较大，最后使体系的分散相尺寸和两聚合物的组成变化影响不大。(4)PA6粘度的变化。结果表明在不加Clay的情况下，PA6粘度高点，HDPE相尺寸就小些，这就说明PA6的粘度对共混物的相形态的确有一定的影响，加入4 phr Clay后，高粘度PA6中HDPE相尺寸减小没有低粘度PA6体系明显，而且最后两个体系中HDPE相尺寸比较接近。 当HDPE接枝AA后，与PA6和Clay有较好的相互作用，从而Clay在PA6／PEAA中有较好的分散，少量的Clay聚集在两相的界面。同PA6／HDPE体系类似的是，随Clay量地增加，HDPE相被拉长，进而体系形成双连续结构。由于Clay较好的剥离和分散，与PA6、PEAA有较好的相互作用，从而较大地提高了体系的拉伸模量，并且由于分散的层状Clay阻碍了链段的运动，从而降低了两相的结晶度和结晶温度，而无定型区的增加也一定程度上有利于两相的相容。 不管是HDPE、PEAA为主相还是PA6为主相，Clay对体系的增容作用表现在与两相的相互作用上，相互作用是Clay能提高相容性的主要原因。用PALS、红外光谱分析了Clay和PA6、PEAA之间的相互作用，并用Lipatov理论分析了增容机理，说明Clay对HDPE／PA6共混体系的增容作用要优于PEAA／PA6共混体系。
The dissertation consists of two parts. First, study on HDPE/clay and PA6/clay nanocomposites; second, the compatibilizaion effect of clay on PA6/HDPE and PA6/PEAA blends. All composites were prepared via melt compounding.1. Study on the HDPE/clay and PA6/clay nanocompositesFor HDPE/clay and PEAA/clay composites, the size and concentration of free-volume in composites were investigated by PALS, and the relationship between free-volume properties and modulus was studied. The results indicated that most of the clay platelets are not intercalated in HDPE, resulted in lower modulus of the composites. In comparison, clay exfoliated and dispersed in PEAA better than that in HDPE matrix, resulting in more interfaces and higher free volume strength (I_3). Consequently, the modulus of the composites increased.For PA6/Clay composites, the dispersion of clay and the properties were investigated by XRD, SEM, TEM, and DSC. The results showed that the clay was exfolicated and dispersed well in PA6. At low shear rate, the viscosity of PA6 decreased with the addition of clay. However, when the shear rate was larger than 3000 s~(-1), the viscosity of PA6/clay was higher than pure PA6. Moreover, the effect was little when 1-4 phr clay was added in PA6. Because of finer dispersion of clay in PA6 and good interaction between PA6 and clay, the clay layers prevented the mobility of PA6 chain segments in certain extent and reduced the crystallization temperature.2. Compatibilizaion effect of clay on PA6/HDPE and PA6/PEAA blendsFor PA6/HDPE system, the compatibilization effect of clay was analyzed according to four factors: (1) Clay content. The HDPE domain size decreased dramatically with the increment of clay content. XRD and TEM results showed that the clay platelets mainly dispersed in PA6 phase and enriched around the interface between PA6 and HDPE. With the increment of clay content, the clay layers which enriched around the interface increased and the thickness of interface also increased.(2) Processing parameters (including rotation speed and mixing time). The variation of rotation speed: for PA6/HDPE (70/30) blend, the HDPE domain size was the smallest when the rotation speed was 40 rpm. With the increment of rotation speed, the HDPE domain size increased. Adding 4 phr clay into this blend, the morphology began to be stable at 40 rpm or faster. The variation of mixing time: for PA6/HDPE blend, with the increment of mixing time, the HDPE domain size decreased. For PA6/HDPE/1 phr clay, HDPE domain size decreased, however, with the increment of mixing time, the HDPE domain size also decreased. When adding more clay into this blend and mixed same time, the HDPE domain size decreased further, and with the increment of mixing time, the domain size began to be stable. (3) The composition of PA6/HDPE. The HDPE domain size (PA6/HDPE-90/10 and 70/30) was lager than that of PA6 in HDPE/PA6=90/10 and 70/30 blends for the blends without clay. When adding 2 phr clay into these blends, the dispersed domain size decreased to a similar level. (4) PA6"s viscosity. The higher is the PA6"s viscosity, the smaller the HDPE domain size is. However, when adding 4 phr clay into these blends, the HDPE domain size decreased to a similar level.For PA6/PEAA system, there were strong interaction between PA6, PEAA and clay. The clay was exfolicated and dispersed well in PA6/PEAA blend, and partial clay sheets enriched around the interface. With the increment of clay content, the PEAA domain was elongated and finally formed co-continuous morphology. Because of the fine dispersion of clay and its strong interaction with PA6 and PEAA, the tensile modulus increased dramatically. The dispersed clay platelets prevented the mobility of PA6 chain and induced the decrement of crystallization temperature and crystallinity. The increment of amorphous portion also induced the compatibility of HDPE and PA6.Whether PA6 was the continuous phase or not, the interaction between clay and the matrix was the most important reason that determines the compatibilization effect of clay. Lipatov theory was used to analyze the compatibilization mechanism.
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