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Effects of Compatibilizer and Post-extrusion Stretching on Properties of Plastic Barrier Films

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The effects of differently tunctionalized polypropylene (PP) and styrene-ethylenebutene- styrene copolymer (SEBS) on different properties of stretched-extruded films of PP/EVOH blend were examined. The effect of melt stretching after die was also studied, The stretched films of the original and polymer-g-diethyl maleate (OEM) modified blends showed laminar morphology, whereas their maleic anhydride (MA) functionalized counterparts showed fibrillar morphology. Rheology of the neat polymers along with their straight and compatibilized blends was studied to assess the quality of mixing under the actual conditions of blending in a counter-rotating twin-screw extruder to control and retain laminar morphology. Differential scanning calorimetry (DSC) tests showed a higher rate of interactions in the case polymer-g-MA modified blends. The SEBS-modified blends showed a lower elasticity at low temperatures. Mechanical properties were improved for almost all modified blends. SEM Micrographs revealed that as a result of melt-stretching post-extruding stretching a finely dispersed EVOH phase in PP matrix was obtained in the case of polymer-g-MA compatibilizer, whereas a laminar one was obtained in the case of polymer-g-OEM compatibilizer. The lowest permeability to oxygen gas was observed for DEM-grafted polymers. The SEBS-g-DEM modified blends showed a barrier performance 90% better than that of pure matrix (PP) and 60% better than that of the original stretched blend.

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