Control The Crystallization Behavior Of Dynamic Vulcanized Polyolefin

Thermoplastic vulcanizates(TPVs)is an elastomer prepared by dynamic vulcanization,which consists of a large amount of rubber(50-80wt%)as dispersion and little thermoplastic(20-50wt%)as continuous.Due to the outstanding properties and special recyclability as a "green material",TPVs have attracted much attention As the continuous,thermoplastic is a significant factor in controlling properties.However,there are limited studies on TPV crystallization,and most of them concentrate on toughening.Based on mature products,it is important to prepare high performance TPV via crystallization study and broaden the application.For the first part,we focused on the special interfacial crystallization in dyn'amical vulcanized POE/PP blends via 'controlling the molecular weight of PP and analyzed the relationship between crystal structure and mechanical properties.For high molecular weight PP chains,approximately in 580,000,have low mobility can be easily maintained and oriented by POE,which vulcanized by 5phr DCP,in dynamic vulcanization and phase separation,and then became nuclei to induce interfacial crystallization.In contrast,for low molecular weight PP(Mw?300,000)chains,have high mobility and are hard to maintained and oriented.The low molecular weight PP are hardly maintained and oriented at interface to induce interfacial crystallization,even it is prepared with POE in high crosslink degree.Besides,we design a sandwich experiment to observe the interfacial crystallization process via POM.In phase morphology results,we found out that phase inversion is still an important factor for PP crystallization.We compared the blend within 1 DCP and 5 DCP that prepared by low molecular weight PP,approximately in 300,000,and found out the PP with wider thickness benefits crystallization.Last,we combined the results of phase morphology and crystallization behavior to analyze their relationship and effect of molecular weight.In another part of the study,we introduced ? crystal by adding 0.1 wt%TMB-5 to EPDM/PP TPV,and studied the properties,structure and their relationship.In experiment,EPDM/PP TPV with ? crystal helps improve the tensile strengthen,elasticity etc.When ? crystal increase to 84%,tensile strengthen from 17MPa to 27MPa.The maximum improvement in permanent set increase to 50%.Controlling the crystal composition of TPV by quenching and last processing temperature,we found out there is no influence on phase morphology and rubber network and improvement on mechanical properties mainly contributes to crystal structure.Besides,we related the result of SEM and mechanical properties and then found out that the loose structure benefits to energy absorbing to improve elasticity.From the WAXS result of EPDM/PP TPV in stretching,the ? crystal deformed and then got oriented to strengthen TPV.Meanwhile,we controlled the ? crystal content via changing the final processing temperature and quenching,and also studied their relationship to mechanical properties.