Structure And Properties Of Functional PP-B/EPDM TPV

Thermoplastic vulcanizate(TPV)based on polypropylene block copolymer(PP-B)/ethylene-propylene-diene monomer(EPDM)blends was prepared by dynamic vulcanization.The mechanical properties,morphology and dynamic viscoelastic behavior such as Mullins effect with its reversibility,compression set with its reversibility and stress relaxation with its reversibility,were researched systematically.The influences of the weight ratio of rubber and thermoplastic on the properties of TPV were investigated.Superhydrophobic surfaces were constructed by molding method where the polypropylene block copolymer PP-B/EPDM TPV was used as raw material and series metallographic sandpaper were used as template.The main results were shown as below:(1)The PP-B/EPDM TPVs with different weight ratio were prepared by dynamic vulcanization,the mechanical properties and micro-structure of the prepared PP-B/EPDM TPVs were investigated systematically.The FE-SEM observation showed that the crosslinked EPDM particles,with the dimensions of 5~7 μm,were dispersed evenly in the etched TPV surface.(2)The Mullins effect of PP-B/EPDM TPV under compression mode,together with its reversibility behavior was investigated systematically.The results showed that an obvious stress softening phenomenon could be observed in the uniaxial loading-unloading cycles during the compression test.Increasing the heat-treatment temperature and the heat-treatment time could improve the reversibility of the Mullins effect;moreover,during the second uniaxial loading-unloading cycle,the Mullins effect of TPV had almost completely reversibility when the heat-treatment temperature was close to the Tm of PP-B matrix.(3)The Mullins effects of EPDM vulcanizate,PP-B and the EPDM vulcanizate reinforced by ZDMA were researched respectively.The results showed that Mullins effect could be significantly enhanced with increasing compression strain and ZDMA dosage.Compared with that of PP-B/EPDM TPV,the EPDM/ZDMA vulcanizates had the relatively lower internal fricion loss and maximum stress.During the uniaxial loading-unloading cycle under compression mode,the stress softening phenomenon of PP-B was more obvious than that of EPDM vulcanizates and TPVs,indicating that the PP-B was the main factor which would lead to the stress softening.It should be noted that there was one common law,increasing the compression strain,the trend of stress-strain curve during the cyclic uniaxial compression test was same as that of the uniaxial compression test,indicating that the previous compression had little influence on stress-strain response of the subsequent compression.(4)The compression set of PP-B/EPDM TPV and its reversible recovery were researched;and the influences of blending ratio and heat-treatment temperature on the reversible recovery of compression set,together with the forming mechanism and the physical model construction of the reversible recovery of the TPV,were investigated systematically.Experimental results showed that increasing the EPDM content in TPV and increasing heat-treatment temperature would lead to the fast recovery of compression set and improve the recovery degree obviously;moreover,the TPV had the best reversible deformation ability when the heat-treatment temperature was 140 oC.The reversible recovery mechanism was discussed based on the microstructure characteristic and deformation recovery feature of the prepared TPV.The physical model construction during the reversible recovery of the TPV were carried out,and the orientation of the thermoplastic resin phase and the elastic recovery of the rubber phase in TPV could provide a driving force for the recovery of the compression set effectively.The generalized Maxwell model could be used to fit the experimental data of reversible recovery of deformation.(5)The stress relaxation behavior of PP-B/EPDM TPV was researched and the mechanism of stress relaxation was carried out in-depth discussion;moreover,the main factors related to stress relaxation were also investigated.The generalized Maxwell model with seven elements was used to describe the process of stress relaxation successfully.The influence of heat-treatment temperature on the reversible recovery of stress relaxation was investigated systematically.Experimental results showed that the stress relaxation was enhanced with the increasing PP-B dosage,and increasing heat-treatment temperature would lead to the better recovery of stress relaxation.(6)Superhydrophobic surfaces were constructed by molding method where the PP-B/EPDM TPV was used as raw material and series metallographic sandpaper were used as template.Microcosmic morphology observation showed that the micron scale rough surface with high fidelity could be prepared by using the metallographic sandpaper as molding template,and the thickness of superhydrophobic layer was 60 μm or so.Wettability test showed that the series roughness surfaces of TPV prepared by molding with sandpapers had strong hydrophobicity character;moreover,the contact angles of all molded surfaces were 150° above,the rolling angles of surface molded with W5,W7 and W10 type sandpapers were less than 10°.The superhydrophobic TPV surface moulded with W10 type sandpaper had the best hydrophobicity.The hydrophobicity character was described quantitatively by Cassie model,the ratio of the liquid/solid interface in the area of molded TPV and water-drop was sharply decline to 20 %.