Construction And Properties Of Functional PP/EPDM TPV Superhydrophobic Surface

Polypropylene(PP)/EPDM thermoplastic vulcanizates(TPV)were prepared by dynamic vulcanization method,the Mullins effect and non-isothermal crystallization kinetics under its tearing mode were studied,and the non-isothermal crystallization behavior was described by using Avrami and Ozawa equations;the template method was used to functionalize the TPV surface by using etched aluminum foil or metallographic sandpaper as a template to obtain TPV films with superhydrophobic and superoleophilic behavior,the influences of different etching times of aluminum foil as a template on the superhydrophobic properties of TPV films and the stability of TPV films under harsh environments were systematically researched,the surface microstructure was characterized and the self-cleaning behavior of functional TPV surfaces was characterized;a new type of continuous operating"straight-through"oil-water separation device was constructed to explore the possibility of applying TPV films for oil-water separation,the influence on the oil-water separation effect was systematically studied,by controlling the gap of the loaded rolled TPV films,the separation pressure,and different types of oil,the mechanism of oil-water separation was also proposed,and the durability of TPV films used for oil-water separation was tested.The results were as follows.(1)The Mullins effect and reversible recovery of PP/EPDM TPV in tearing mode were studied.It was shown that there was a significant Mullins effect and demonstrated stress softening in PP/EPDM TPV under the tear mode,and it was becoming significant with increase PP content,the reversible response of the Mullins effect showed a significant temperature dependence,and the Mullins behavior of PP/EPDM TPV showed the excellent reversibility after heat treatment.The results on the non-isothermal crystallization behavior of PP/EPDM TPV showed that the Avrami equation can describe the non-isothermal crystallization behavior of pure PP and PP/EPDM TPV well;however,the Ozawa equation cannot describe the non-isothermal crystallization behavior of PP/EPDM TPV;for pure PP and PP/EPDM TPV,the crystallization rate during non-isothermal crystallization increased with increasing cooling rate;PP/EPDM TPV showed higher initial crystallization temperature(T₀)and crystallization termination temperature(T_c)compared to that of pure PP at the same temperature cooling rate,this suggested that the vulcanized EPDM particles acted as a nucleating agent in the TPV crystallization process and promoted the crystallization of PP.(2)PP/EPDM TPV superhydrophobic and superoleophilic film was prepared by molding method with diluted hydrochloric acid(HCl)etched aluminum foil as template,the microscopic morphology of the surface of aluminum foil after different etching times and molded TPV was observed by FE-SEM,the results showed that the rough structure of the TPV surface was the fibrous tear band which was created by the plastic deformation of the resin phase PP during the peeling process from the template,which caused the air to be intercepted between the complex tear band and drastically reduced the contact area between the droplets and the TPV film,leading the excellent superhydrophobic properties;compared with that of the TPV films molded with unetched aluminum foil,the roughness of TPV film surface was increasing with increasing etching time,especially the most obvious surface roughness of TPV films molded with aluminum foil with etching time of 10 min;wettability results showed that the hydrophobicity of the TPV film surface was significantly improved after etched aluminum foil was molded as a template,and the TPV film surface obtained by etching the aluminum foil template for 10 min showed the best superhydrophobicity(contact angle of 157.9°±2.9°and roll angle of 4.3°±1.1°)and the molded TPV film with excellent abrasion resistance,acid and alkali solvent resistance and good heat resistance;self-cleaning performance test showed that the superhydrophobic and superoleophilic TPV film possessed the high water repellency and exhibited excellent self-cleaning performance by carrying away the dust and impurities attached to it without being attached by liquid stains;a straight-through oil-water separation device was used to test the superhydrophobic and superoleophilic TPV films for oil-water separation,the results showed that PP/EPDM TPV films could be used for oil-water separation and the oil-water separation efficiency could achieve a maximum of 100%when the separation pressure was lower than 5 k Pa.(3)In order to prepare superhydrophobic and superoleophilic PP/EPDM TPV film for oil-water separation experiment with large area,the surface of superhydrophobic and superoleophilic PP/EPDM TPV film was prepared by molding method using metallographic sandpaper as templates.Compared with the super hydrophobic and super oleophilic TPV film molded by etched aluminum foil,the TPV surface molded by metallographic sandpaper was not much rougher but still achieved the requirements of superhydrophobic surface,especially the TPV surface molded by W10 sandpaper has a contact angle of 155.2°±0.7°and a rolling angle of 5.1°±1.2°,which means it was a superhydrophobic surface and can be used for oil-water separation;the superhydrophobic and superoleophilic PP/EPDM TPV film was rolled and put into a straight-through valve to form a direct suction pressure response valve,and after that,oil-water separation experiments were performed,the factors affecting the oil-water separation capacity and separation efficiency of direct suction pressure response valves,including the separation membrane gap,separation pressure,oil type were systematically studied,the results showed that the direct suction pressure response oil-water separation device provided excellent oil-water separation capacity and its oil-water separation capacity can be significantly influenced by separation film type,separation film gap and oil type;it achieved the best oil-water separation performance and the oil-water separation efficiency was as high as 98.52%when the film gap of the rolled film in the oil-water separation device was 50?m and the separation pressure was4 k Pa.