| The dissertation consists with two parts. First, study on the preparation, structure and properties of acrylic acid (AA) grafted high density polyethylene (HDPE)/ montmorillonite (MMT) nanocomposites; second, study on the preparation, structure and properties of vinyl triethoxysilane (YDH151) grafted HDPE/MMT nanocomposites.1. Preparation, structure and properties of HDPE~g~AA/MMT nanocompositesMelt grafting reaction of HDPE with AA was performed in ThermoHaake Rheomix and HDPE-g-AA with high grafting degree and high grafting efficiency was prepared. The change of torque indicated that the graft copolymerization was existed during melt compounding. The extent of grafting was analyzed by FTIR and element analysis. When AA content was less than 10wt-%, the extent of grafting increased with increasing the content of AA, and the grafting efficiency maintained in a high level of about 80%. However, when AA content exceeded 10wt.-%, the increment of the extent of grafting level off and the grafting efficiency decreased remarkably.Afterward HDPE-g-AA/MMT composites and HDPE/MMT composites were prepared via melt compounding. XRD and TEM results indicated that AA promoted the dispersion and exfoliation of MMT into HDPE. Most of the MMT has exfoliated into single sheets in HDPE-g-AA/MMT composites. While in HDPE/MMT composites, most of the MMT aggregates are not intercalated by PE chains. Consequently, with increasing MMT content, the tensile strength and Young's modulus of HDPE-g-AA/MMT nanocomposites increased, while that of HDPE/MMT composites decreased. Moreover, the addition of MMT to HDPE-g-AA decreased the melting temperature and the degree of crystallization of the matrix. These changes may be attributed to high interfacial adhesion between HDPE-g-AA matrix and exfoliated clay, which reduces the mobility of crystallizable PE chain segments, and subsequently reduces the crystallization ability. In comparison, the addition of MMT to HDPE did not affect the crystallization behavior of the later.2. Preparation, structure and properties of HDPE-g-YDH151/MMT nanocompositesMelt grafting reaction of HDPE with YDH151 was performed in ThermoHaake Rheomix and the melt grafting procession was studied. The extent of grafting was analyzed by FTIR andelement analysis and thermal properties of HDPE-g-YDH151 were studied by DSC measurement. When adding DCP to HDPE, the melting temperature and the degree of crystallization of the matrix decreased because of the crosslinking reaction of HDPE. While adding YDH151 to this system, the torque decreased and the melting temperature and the degree of crystallization of the matrix increased. These changes may be attributed to the competition between the grafting of YDH151 and HDPE and the self-crosslinking of HDPE, and the grafting resisted the crosslinking reaction. Furthermore the addition of liquid YDH151 decreased the maximal torque. With increasing the content of YDH151, the grafting degree increased and the grafting efficiency decreased. However, the content of DCP cannot be added too much so as to avoid the crosslinking reaction between YDH151 and HDPE. Moreover when AA content exceeded 10wt.-%, the increment of the extent of grafting level off and the grafting efficiency decreased remarkably.Then HDPE-g-YDH151/MMT composites and HDPE/MMT composites were prepared via melt compounding. FTIR proved that there were interactions between YDH151 and MMT sheets. XRD, SEM and TEM results indicated that YDH151 promoted the dispersion and intercalation of MMT into HDPE. Most of the MMT has intercalated in HDPE-g-YDH151/MMT composites. While in HDPE/MMT composites, mpst of the MMT aggregates are not intercalated by PE chains. Moreover, the composite of HDPE-g-YDH151(8phr)/2phrMMT formed a good crosslinking net, the MMT act as crosslinking points. Consequently, the mechanical properties of this composite is good: the elongation at break impoved 29% and tensile modulus increased 32%. While, increasing the content of MMT again, the mechanical properties decreased. To the sy...
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