Research On Cushioning And Liquid Absorption Characteristics Of Expanded Polyvinyl Alcohol

With the continuous development of social productivity and economy, the circulation of allkinds of products in different areas is more and more frequent. The liquid products have goodliquidity, and the productivity packaging is especially important in the process of circulation.Expanded polyvinyl alcohol (PVA) is a new kind of foam plastic, and has many advantages, e.g.qualitative light, high strength and shock absorption, etc., at the same time, expanded PVA hasgood liquid absorption and liquid retention properties. When expanded PVA is used as thepackaging material of liquid product, it not only can have the effect of energy absorption, butalso once liquid products have leakage accidents, expanded PVA can absorb liquid quickly andtimely. Therefore, the development research of expanded PVA as packaging material has a broadapplication prospect.By combining experimental research and theoretical analysis, cushioning properties and liquidabsorption properties of expanded PVA were studied, which could provide some references forpackaging application of expanded PVA. The major research results were followed by these:The stress-strain relationship was obtained by the static compression tests, and therelationships between mechanical properties and density and strain rate were analyzed. Bycombining SEM images of expanded PVA during compression, the compression deformationmechanism of expanded PVA was analyzed. The results showed that the stress-strain curve ofexpanded PVA included three different stages, namely linear elastic zone, yield platform zoneand dense zone, the initial elastic modulus and plateau stress of expanded PVA increased as thedensity increased, when the densities of expanded PVA were0.095g/cm3,0.117g/cm3and0.143g/cm3, the initial elastic modulus values were1.489MPa,2.752MPa and4.251MPa, andplateau stress values were0.138MPa,0.237MPa and0.347MPa, respectively. Expanded PVAhad a certain strain rate sensitivity, and plateau stress increased as strain rate increased;Compression deformation mechanism of expanded PVA derived from bending of hole wall, andthe effect of pore fluid could be neglected as cell size of material increased.The effect of temperature and relative humidity on mechanical properties of expanded PVAwas studied by tests, the results showed the change of temperature or relative humidity affectedinternal moisture contents of expanded PVA, in other words, moisture contents of expanded PVAincreased as relative humidity increased, or decreased as temperature rose. The initial elastic modulus, plateau stress and energy absorption value of expanded PVA on platform zoneincreased as relative humidity increased, or decreased as temperature rose, and the initial elasticmodulus value was from0.8MPa to6.5MPa, plateau stress value was from0.08MPa to0.55MPa,energy absorption value of expanded PVA on platform zone was from0.064J/cm3to0.25J/cm3.Finally, on the basis, the constitutive relation model of expanded PVA was established includingthe parameter of density, strain rate, temperature and humidity, and then was verified. The modelcould easily predict mechanical properties of expanded PVA under different conditions.Liquid absorption behavior of expanded PVA under different influence factors was studied byliquid absorption tests, the influence factors included the density of material, liquid type, liquidtemperature and concentration, etc., and the effect of which on liquid absorption properties ofexpanded PVA was described. The results showed absorption rate of expanded PVA was morethan ten times as the quality of material itself, and liquid retention rate was10%~15%. Bycombining pore structure and hydrophilic group of expanded PVA, liquid absorption mechanismof expanded PVA was analyzed, which indicated a large amount of liquid flow into internalporosity of material by physical absorption. And on the basis, some suggestions were proposedto improve liquid absorption properties of expanded PVA.Cushioning properties and liquid absorption properties of expanded PVA were studiedessentially by the above research, which has important practical significance for packagingapplication of expanded PVA in the late research and provides experimental data and theoreticalbasis.