Polymer Engineering Faculty Research


Basic studies on development of structure hierarchy in tubular film blown dynamically vulcanized PP/EPDM blend

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The processing characteristics and structural hierarchy development in a tubular blown, dynamically vulcanized polypropylene/ethylene—propylene—diene monomer rubber (PP/EPDM) blends were investigated. The semi-crystalline PP phase exhibited a* and c-axis orientations with the a* oriented populations dominating low draw-down ratio (DDR) conditions. At high DDR, both a* and c-axis oriented populations were observed. Little or no preferential orientation was detected in the discrete EPDM phase using dichroism studies. The blown films were found to exhibit an unusual asymmetric structure: The PP phase was found to fibrillate at the outside surface while the inner surface remained relatively featureless. This was attributed to disproportionately rapid cooling of the outside surface by the air stream blown externally onto the film being extruded. This, in turn, resulted in solidification of very thin PP surface layers that caused their fibrillation under the heavy stresses they had to endure. Increasing the blow-up ratio was found to expand this web-like surface texture. As a result of this fibrillation mechanism, the increase of both the blow-up ratio and draw-down ratio was found to reduce the mechanical properties.

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Rubber Chemistry and Technology





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