Structure And Properties Of Functional HDPE/EPDM TPV

Thermoplastic vulcanizates(TPV)based on high density polyethylene(HDPE)/ ethylene-propylene-diene terpolymer(EPDM)were prepared via dynamic vulcanization.The mechanical properties,morphology,compression set and its reversibility,Mullins effect and its reversibility,strengthening effect of Mullins effect under compression mode were investigated systematically.The influences of blending ratio,POE dosage in resin phase and paraffin oil dosage in resin phase on the properties of TPV were also researched.The flexible superhydrophobic functional material based on HDPE/EPDM TPV was prepared by using metallographic sandpaper and etched aluminum foil as templates.The effect of template type,molding pressure,molding temperature and etching conditions on the surface morphology and wettability of molded TPV were investigated systematically.The mechanism of superhydrophobic was discussed combined with the classical superhydrophobic theory;moreover,the thermostability,the hydrophobic stability,the acid and alkali resistance of the superhydrophobic TPV surface were studied.The main results were showen as below:(1)The mechanical properties and microstructure of HDPE/EPDM TPV were researched.And the influence of the POE dosage and paraffin oil dosage in the resini phase on the elasticity property of TPV was also investigated.It shows that the mechanical properties of the HDPE/EPDM blends preparaed by dynamic vulcanization were stronger than that of the EPDM vulcanizate.Increasing the HDPE content in TPV,the TPV strength was increased remarkably.Considersing the elasticity,strength and hardness,it can be seen that the property of TPV was well when the weight ratio of HDPE/EPDM was 40/60.FE-SEM observation shows that EPDM vulcanizates particle size was 2~6 ?m and the particles were evenly distributed in the etched TPV surface.Incorporated with POE and paraffin oil in the resin phase,the disadvantages in hardness and permanent deformation of TPV were improved obviously;moreover,the incorporation of paraffin oil in TPV could also improve the the processability of TPV during dynamic vulcanization processing.(2)The research of compression set and its reversibility of series HDPE/EPDM TPV shown that the content of EPDM in TPV has an important influence on the recovery of compression set.The degree of reversible recovery of compression set was significantly increased with increasing of EPDM content in TPV under the same heat treatment condition.Based on the characteristic of TPV etched morphology and its recovery curves,the reversible recovery mechanism was discussed.Combination with the Maxwell model,the reversible recovery curves of TPV was fitted successfully and the relaxation activation energy during the recovery process of HDPE/EPDM TPV was calculated quantificationally.(3)The research on the Mullins effect and its reversibility under compression mode shown that the stress softening phenomenon could be observed obviously during the cyclic loading-unloading compression under the fixed compressive strain.The maximum stress,internal friction and tan? was decreased obviously after the first loading-unloading while only decreased slightly at the later loading-unloading cycles.The residual deformation was increase with the increase of cyclic loading-unloading times.The Mullins effect could recover partically under heat treatment.Increasing the heat treatment temperature was helpfule for the reversible recovery of Mullins effect,and the result showed that the best recovery temperature was 100 ?.(4)The stress-strain behavior and the strengthening effect of Mullins effect under compression mode of CB reinforced EPDM vulcanizate and series HDPE/EPDM TPV were investigated systematically.The mechanical properties of CB reinforced EPDM were significantly improved compared with that of EPDM vulcanizate,and the compression strength and modulus of TPV were also increase with the increasing HDPE content in TPV.During the cyclic loading-unloading under the fixed compressive strain,it could not observed Mullins effect in EPDM vulcanizate.However,the stress softening phenomenon could be observed obviously in CB reinforced EPDM vulcanizates and the TPV.The maximum stress was decreased obviously after the first loading-unloading,and the residual deformation was increase with the increasing of cyclic loading-unloadi times.Moreover,Mullins effect could be significantly enhanced with increasing CB dosage in EPDM vulcanizate and increasing HDPE content in TPV;morevoer,increasing the compression strain also could enhance the Mullins effect.(5)Superhydrophobic and flexibility TPV material was fabricated via molding method by using metallographic sandpaper as template.FE-SEM observation showed that,the micron scale rough surface of TPV with high fidelity could be prepared by using the sandpaper template.The micro plastic deformation in the TPV surface could be observed obviously,leading to the increase of complex surface roughness.Wettability test showed that the roughness surfaces of TPV had strong hydrophobicity,the contact angles were 150o or so while the sliding angles were less than 10o.TPV molded with W10 type metallographic sandpaper had the best hydrophobicity.According to Cassie model,the percent of gas-liquid interface was more than 80 % in the contact interface between the TPV and water droplet,leading to a larger contact angle of the molded TPV.(6)The etched aluminum foil was used as template to fabricate superhydrophobic TPV surface.Wettability test showed that the series roughness surfaces of TPV had strong hydrophobicity,the contact angles were 150o or so while the sliding angles were less than 5o.According to Cassie model,the percent of gas-liquid interface was more than 85 %.Microstructure study shown that,a number of micro plastic deformation in the TPV surface could be observed obviously,leading to the increase of roughness surface more significant than the etched aluminum foil template.Stability of hydrophobic TPV shown that,when the molded TPV was submitted to heat treatment in 2 hour under different temperature,the static contact angle only decreased slightly.The molded TPV surface still had a superhydrophobic property while the heat treating temperature was below 60 ?.After soaking in series of acid and alkali solution,the molded TPV surface still has great static contact angle,but the sliding angle was increases obviously.The superhydrophobic TPV had the stable hydrophobic effect to water drop with different PH value.