Preparation, Structure And Properties Of EVA/CM Functional TPV And Hdpe/Wgrt Tpe

Thermoplastic vulcanizate (TPV) based on ethylene-vinyl acetate copolymer (EVA)/chlorinated polyethylene (CM) blends were prepared by dynamic vulcanization. The morphology, mechanical properties, crystallization behavior and dynamic viscoelastic behavior of EVA/CM TPV were researched systemically. The influence of the reinforcing agent and plasticizer on the properties of TPV was investigated. The NTC effect of the EVA/CM TPV which was prepared by incorporation of carbon black (CB) was studied. The water-swellable EVA/CM TPV was prepared, the influence of hydrophilic substance, the particle diameter of CPNaAA and the water absorbing condition on water absorption were also studied. The mechanical properties and water swelling behavior of the TPV were characterized. The thermoplastic elastomer (TPE) based on the composites of high density Polyethylene (HDPE) and waste ground rubber tire (WGRT) via melt-compounding with the interface compatibility modified by the addition of styrene-butadiene-styrene block copolymer (SBS). The effect of compatibilizer on the mechanical properties, morphology, PTC effect and Mullins effect of the composites were investigated. The results were shown as follows:(1) The EVA/CM TPV were prepared by dynamic vulcanization, the mechanical properties, microstructure and crystallization behavior of the prepared EVA/CM TPV were investigated systematically. Considering the proper mechanical properties, the weight ratio of EVA/CM TPV should range from20/80to40/60. Furthermore, when the weight ratio of the EVA/CM TPV was10/90, the TPV also showed the behavior of elastomer.(2) The influence of HDPE, ZDMA, CB, and SiO2on the mechnical properties of the EVA/CM TPV were investigated. The tensile strength of the TPV was increased when the HDPE was added in the EVA matrix. When the content of ZDMA was only5phr, the tensile strength and the tearing strength were increased by82.4%and33.5%, respectively, and the retention ratio of elongation at break was79.6%. The EVA/CM TPV achieved the best performance of the mechanical properties when the CB content was40phr, and the Shore A hardness decreased due to the increased of the volume of the dispersed phase. With adding of DOP and POE to the EVA/CM TPV, the Shore A hardness of EVA/CM TPV decreased.(3) The fracture surface of the EVA/CM TPV showed the well interface interaction and the strong elasticity. The FE-SEM result showed that the vulcanized CM particles with the diameter of2-5μm were dispersed evenly on the surface of etched TPV. Some obvious tearing strips on the fracture surface of EVA/CM TPV reinforced by ZDMA can be observed, their formation would consume relatively high energy during the fracture process, leading to the obviously improved mechanical properties. There were a large number of particles dispersed on the etched surface of EVA/CM/ZDMA TPV with average diameter of10μm below; moreover, the particles were surrounded by a large number of smaller CM particles. However, the fracture surfaces of TPV incorporated with HDPE were relatively flat, some obvious tearing strips on the fracture surface can be observed.(4) The XRD patterns showed that the intensity of diffraction peaks of EVA crystals in TPV was decreased with the decreasing of EVA content and the grain size was increased. With the strain increasing, the Payne effect of the TPV was obvious, the storage modulus deceased greatly with the EVA content increasing, the Payne effect was enhanced.(5) The conductive polymer composites were prepared by adding CB in the matrix of the EVA/CM TPV, The percolation phenomenon was appeared when the content of CB was higher than8phr. The NTC effect was remarkably when the CB content was14phr, up to two orders of magnitude. Moreover, the tensile strength was increased from5.1MPa to7.8MPa when the CB content was only2phr.(6) WSR was prepared by dynamically vulcanizing EVA/CM blends where the crosslinked poly (sodium acrylate)(CPNaAA) was used as a super water-absorbent resin and dispersed in the CM rubber. Experimental results showed that the water-swelling ratio increased with the content of CPNaAA increased, and the water-swelling ratio increased significantly when the content of CPNaAA content higher than40phr. At room temperature, the water-swelling ratio of EVA/CM/CPNaAA (30/70/60) TPV was728.4%at72h in the distilled water. The repeatability of water-swelling of the TPV showed that the secondary and the third water-swelling rate were much higher than that of the first water-swelling behavior. Compared to the first water-swelling behavior, the time of equilibrium swelling of the second and third water-swelling behavior decreased from93h to48h. Morphology study showed that some significant gaps and large cavities could be found in the surface of dried TPV, leading to the high equilibrium swelling rates in the second and the third water-swelling behaviors; the CPNaAA particles were dispersed randomly in the TPV and the CPNaAA particles were coated with a layer of CM particles, with an average diameter of2μm. The water-swelling ratio of EVA/CM/CPNaAA (30/70/60) TPV decreased greatly in the salt or acid solutions when the medium concentration increased. However, the water-swelling ratio of EVA/CM/CPNaAA (30/70/60) TPV increased slightly at low concentration of alkaline solution, which was caused by ionization of the carboxylic ion. Weak alkaline environment can promote the water-swelling of the TPV increasing.(7) The influence of diameter of the CPNaAA, in-situ prepared NaAA, and in-situ prepared NaAA combined with CPNaAA on the properties of the water-swellable EVA/CM TPV were studied. When the diameter of the CPNaAA was200mesh, the TPV had the higher water-swelling ratio than that of100mesh and300mesh. The WSR prepared by in-situ had high tensile strength, but smaller elongation at break; the water-swelling ratio was low which was caused by high network intensity of the TPV. When the CPNaAA was combined with in-situ-NaAA, the strength and the water-swelling ratio of the TPV were high, the water-swelling ratio of TPV was388.0%at72h in the distilled water.(8) TPE based on HDPE/WGRT composites were prepared by melt-compounding, the composites were compatibilized by styrene-butadiene-styrene block copolymer (SBS). Experimental results indicated that SBS had a good compatibilization effect on the HDPE/WGRT composites. The tensile strength and the elongation at break went through maximum values at a compatibilizer resin content of12phr, the tensile strength and the elongation at break increased from11.8MPa (at0phr SBS) to15.0MPa and185.1%(at0phr SBS) to372.1%, respectively. Morphology study showed that the interface interaction of the HDPE/WGRT composites compatibilized by SBS was strong. The Mullins effect was founded in HDPE/WGRT TPE, the softening appeared obviously after the first loading and the residual deformations accumulation; furthermore, the residual were much higher than that of Mullins effect of conventional filled and unfilled vulcanizates. the HDPE, as a ductile thermoplastic resin is the matrix of the HDPE/WGRT composite, the residual plastic deformation of HDPE lamellae crystals during tensile process resulting in much higher residual deformations.(9) The conductive polymer composites were prepared by adding CB in the matrix of the HDPE/WGRT composites. The PTC effect was remarkably near the melting temperature of the HDPE matrix when the CB content range from8phr to14phr, up to four orders of magnitude.