Construction And Properties Of Superhydrophobic Surfaces Based On LDPE/SBR TPV

In this research,a series of thermoplastic vulcanizates（TPVs）based on low density polyethylene（LDPE）/styrene-butadiene rubber（SBR）blends were prepared by dynamic vulcanization,and the microscopic phase structure,mechanical properties and Mullins effect under tear mode together with its reversible recovery behavior under heat treatment of the prepared TPV were investigated systematically;the non-isothermal crystallization kinetics behavior of the LDPE/SBR TPV and the pure LDPE resin were researched by the differential scanning calorimetry（DSC）and described by Avrami,Ozawa and Mo models,respectively.Moreover,the functional LDPE/SBR TPV films were prepared by molding with the different type metallographic sandpaper and the etched aluminum foil which were used as templates,the wettability behavior of the prepared films was characterized.The winding superhydrophobic and superoleophilic LDPE/SBR TPV films were inserted in the oil-water separation valve of a home-made laboratory oil-water separation device,and the gap of the winding films was used as the pressure response channel for oil-water separation,the oil-water separation was achieved and oil-water separation was characterized quantitatively.The results of the research were showed as below:（1）The"sea-island"microstructure could be observed clearly by FE-SEM in the surface of the LDPE/SBR TPV specimen etched by xylene;the mechanical properties results showed that pure LDPE resin and LDPE/SBR TPV exhibited the stress-strain behavior of"hard and strong"of thermoplastic and the"soft and tough"of vulcanized rubber,respectively;and the tensile strength,the elongation at break and the hardness of TPV were increased obviously with increasing LDPE dosage in the dynamically vulcanized blends;the non-isothermal crystallization behavior of the pure LDPE and the LDPE/SBR TPV showed that both the Mo model and the modified Avrami model could describe the non-isothermal crystallization behavior well;however,the Ozawa model could not be applicable to describe the non-isothermal crystallization behavior;and it could also be found that the TPV had the higher crystallization onset temperature（T₀）and the higher peak crystallization temperature（T_p）compared with that of the pure LDPE at the same cooling rate;it could be found that there was a significant Mullins effect in the load-unload cycle process of LDPE/SBR TPV under tear mode,and the reversible recovery behavior of the Mullins effect in LDPE/SBR TPV was increased remarkably with increasing the heat treatment temperature,and the best reversible recovery could be achieved when the heat treatment temperature was 105°C.（2）The surface of the series LDPE/SBR TPV films was molded with metallographic sandpaper with different grit sizes and then the metallographic sandpaper was stripped off,the prepared TPV surface was hydrophobic,and it should be noted that when the TPV with LDPE/SBR weight ratio of 60/40 was used as raw material and the W14 sandpaper was used as a template,the surface of the prepared TPV films had a water contact of 158.0±1.1°,a water rolling angle of 7.3±0.6°and a surface energy of12.91±1.0 m N/m,indicating that the TPV films with the excellently superhydrophobicity could be obtained successfully.In order to further improve the hydrophobic behavior of the surface TPV films,TPV films were prepared by molding with a home-made etched aluminum foil template which had the finer rough microstructure;moreover,when the etching time of the aluminum foil was 10 min and the LDPE/SBR weight ratio of TPV was 60/40,the prepared TPV films had a water contact angle of 163.1±1.7°,a water rolling angle of 4.0±2.0°and a surface energy of11.92±0.4 m N/m.Compared with the TPV films prepared by molding with W14sandpaper,TPV films molded with the etched aluminum foil had the increasing hydrophobicity,and stability tests showed that the TPV films prepared in this research had the well environmental and chemical stability,as well as the well resistance to the high temperatures and the mechanical wearing.It was shown that the superhydrophobic films prepared by the template method were not a simple replica of the surface of the template;however,a large number of fibrous rough structures in the molded TPV surface could be found obviously,which were formed by the plastic deformation of the resin phase LDPE during the stripping the template from the TPV matrix,leading to the excellent superhydrophobic behavior.（3）The prepared TPV films molded with etched aluminum foil had a water contact angle of 163.1±1.7°and could remain almost constant for 30 min,indicating the good superhydrophobic stability;the research on the lipophilic behavior of TPV films showed that the specimens exhibit the good superlipophilic behavior both in air and under water.Based on the good superhydrophobic and superlipophilic properties of the TPV films,the winding TPV films was inserted in a self-assembled oil-water separation device,and testing results showed that the TPV films had the good oil-water selection ability for a variety of oils;moreover,when the interlayer gap D_m and the external pumping force P_mwere 50μm and 9 k Pa respectively,the oil-water separation efficiency of the TPV films was greater than 99%,indicating that the TPV films could effectively separate the oil-water mixture effectively.