Preparation、Morphology And Properties Of PP/POE-g-MAH/EVOH Barrier Material With High-toughness Property

Modification of PP is one of the active field in the plastic processing industry, the chainstructure is unique, not only homopolymer structure change is big, copolymer modifiedpotential is more larger especially on the barrier properties of the modified relatively to the PE,which can be made into excellent resistance performance of packaging material. In order toimprove the barrier properties, this subject adopts the best blocking performanceethylene/vinyl alcohol copolymer (EVOH) to be modified, but they are incompatible. Thistopic use POE-g-MAH as compatibilizers in improving the compatibility at the same timeimprove the toughness of the blend. The mechanical, barrier, morphology, rheologicalproperties and crystallization kinetics were investigated in terms of tensile/impact testing, oilabsorption, rotational rheometer/capillary rheometer，differential scanning calorimeter (DSC),FTIR and scanning electron microscopy.The experimental results of mechanical properties and barrier properties showed thatimpact strength and tensile strength of material reached a maximum which are77.317KJ/m2and30.78MPa, respectively, when the ratio of blocking material to PP/POE-g-MAH/EVOH=90/10/10. Compared with pure PP blending materials, impact strength and tensile strengthincreased by17.45times and69.10%，respectively. The oil absorption value of Blendingmaterial system were decreased with increasing of EVOH content, namely blockingperformance of blocking material system increased with increasing of EVOH content. TheSEM shows that the system of dispersed phase EVOH in the matrix phase has certain lengthto diameter ratio, the whole present the oval and the partial rendering layer structure, alsocoupled with the excellent EVOH itself blocking performance which to a certain extent, canhave the effect of extension of the seepage path, so as a whole the barrier properties of theblend is improved. The effect of EVOH content on the rheological behavior of PP/POE-g-MAH/EVOHblends was investigated. The results showed that PP/POE-g-MAH/EVOH blend ispseudoplastic fluid, the shear stress required for first increases then decreases along with theincreasing of EVOH content under the same shear rate and the consistency of K appeared thesame trend of first increases then decreases with increasing of EVOH content. With theincrease of shear rate blend viscosity varies has a lower trend show the phenomenon of shearis thinning. Apparent viscosity of system showed a trend of decrease after the first increasewith the increasing of EVOH content. Sticky flow activation energy ofPP/POE-g-MAH/EVOH blend is higher than the blend which did not contain EVOHsuggesting that blend with a strong sensitivity to temperature.The crystallization kinetics of PP/POE-g-MAH/EVOH composites was investigated byDSC. The studies on the isothermal crystallization showed that the Avrami equation can welldescribe the material of isothermal crystallization process, the addition of EVOH changed thenucleation mechanism of PP/POE-g-MAH/EVOH barrier material which can significantlyimprove the crystallization of PP nucleation rate and have the effect of heterogeneousnucleation. With the theory of Hoffman-Weekes, PP/POE-g-MAH/EVOH barrier materialequilibrium melting point is higher than that of PP, which indicates that the addition of EVOHenhances the crystallization of PP perfect degree. Theory of Hoffman-Lauritzen,resultsindicate that the folding free energy in vertical direction of the molecular chain increase,which indicates that the addition of EVOH increased resistance of PP molecular chain incrystal lattice so that hinder the movement of PP molecular chain folds into the crystallattice.The investigation of non-isothermal crystallization showed that the addition of EVOHnot only hindered the growth of crystals and reduces the crystal growth rate but also changedthe nucleation and crystal growth law of PP.The results of POM (Polarized Optical Microscopy) showed that after the EVOH joining,it hinder the growth of the PP spherulite radial emission and the spherulite growth is notperfect which result in PP spherulite size decrease.