| Ethylene vinyl acetate copolymer (EVA) foams, because of their lightweight, softness, good shock absorption, non-toxicity and resistance to chemicals,have been widely used in the manufacture of soles of athletic shoes, luggagelining, thermo-insulating materials, and sound-proof materials. Nonetheless, aslightweight material, EVA foams are fraught with weaknesses such as pronenessto deform, low tear resistance, and low rebound resilience, which consequentlylimit its application. Thus, it is of great significance to develop new compositefoams based on EVA with properties such as low density, softness, high reboundresilience and excellent compression set. This paper discussed the preparation ofEVA-based nanocomposites with outstanding comprehensive properties, byintegrating nano modification and polymer blending modification. The followingthree aspects were highlighted:(1) Organic modification of montmorillonite (MMT) and its effect on theproperties of EVA foams. The dispersion of pre-modified MMT in the EVAmatrix was examined. The cell structure of EVA/MMT composite foams andtheir physical properties were discussed. MMT was modified by differentcationic quaternary ammonium surfactants. The effect of length and quantity ofcarbon chain in the surfactants on MMT intercalation was examined. The effectof different organic montmorillonite (OMMT) on the microstructure andcomprehensive properties of the EVA-based foams was investigated. After beingorganically modified, the dispersion of OMMT in the EVA matrix and theinterfacial compatibility between them was improved. OMMT played the role ofheterogeneous nucleation in the EVA foaming process. The length and quantityof carbon chain of cationic quaternary ammonium surfactant affected themicrostructure and further, affected the physical properties of the EVA/OMMTnanocomposite foams. Through the analysis of the effect of the functional groupstructure and the dispersion of the MMT modified by dioctadecyl dimethyl ammonium chloride on EVA/OMMT composite foams, the enhancing andtoughening mechanism of OMMT layers to EVA foams was analyzed. Byinvestigating the physical properties and microstructure properties of theEVA/OMMT nanocomposite foams, the threshold of OMMT particle size inEVA heterogeneous nuclearation foaming process was explored.(2) The reinforcing modification of ethylene octene copolymer (POE) onEVA foams was studied. The compatibility between POE and EVA and thestorage modulus of the composite were examined. POE/EVA foam was producedusing mixture and blending method. The impact of different POE content on themorphology and physical properties of the composite foams was investigated. Itwas found that the rebound resilience of the composite foams significantlyincreased with the addition of POE. The EVA/POE/OMMT foaming system wasthen studied. The cell morphology and comprehensive properties of thecomposite foams were investigated. The effect of POE on the EVA/OMMTfoaming system was analyzed. In addition, a theoretical analysis on the POEimproving the rebound resilience of the composite foams had been discussed.(3) The reinforcing modification of ethylene propylene diene monomer(EPDM) on EVA foam material was discussed. Firstly, EPDM was added to theEVA matrix and the compatibility between EPDM and EVA matrix wasexamined. The impact of different ratios of EPDM to the EVA matrix on themicrostructure and physical properties of foams were investigated. With theaddition of EPDM, the cell diameter of the composite foams became smaller andthe thickness of cell wall increased. The compression set of both EVA/EPDMfoams and EVA/POE/EPDM/OMMT composite foams was significantlyimproved. Then, composite foams with and without EPDM were compressed toobserve the difference of cell morphology at a specific time point. The effect ofEPDM on deformation reversal of the composite foams was investigated and themechanism of EPDM improving compression set was analyzed. |
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