Studies On The Preparation And Properties Of Modified SEBS Thermoplastic Elastomer

Poly(styrene-b-ethylene-co-butadiene-b-styrene)(SEBS)has attracted the wide attention because of its good elasticity,excellent weather resistance,low temperature resistance and excellent color properties.However,some disadvantages,such as the permanent deformation,poor heat resistance and high price have restricted the expanding of SEBS's applications.The physical and mechanical properties of SEBS will improve significantly after the blending modification by oil,resins,fillers and additives.A series of modified SEBS were prepared by using a white as a plasticizer,thermoplastic polypropylene(PP)as a modifier and inorganic nano fillers as the reinforcing agents.These composite materials were further characterized and their properties were also evaluated.Subsequently,the relationship between the properties and structures of modified SEBS were investigated.The main contents of this thesis were summarized as follows:1.The influence of the filling oil content on the mechanical and flowing properties of SEBS thermoplastic elastomer were investigation.The optimization mass ratio of filling oil(15# white oil)to SEBS was determined as 100:120.2.The SEBS/PP composite thermoplastic elastomers were prepared by the modification of oil-filled SEBS with three polypropylene(PP,M2600R),PP(320),PP(040)with different chemical structures.The best modifier for SEBS composite materials was proved as PP(M2600R)according to the comparison of the physical and mechanical properties of three SEBS/PP composite materials.The experiment results showed that the rigidity of SEBS/PP composite materials improved at the addition of PP and then the flexibility of composite materials decreased.The best physical and mechanical properties of SEBS/PP composite materials were obtained when the PP content was 50 phr(quality ratio).3.Two fillers including calcium carbonate and talc powers were treated with titanate coupling agent ND-201,silane coupling agent KH550 and the combination of ND-201 with KH550,respectively.The SEBS/PP/Fillers composite materials were further prepared by the blending of modified fillers with SEBS,PP and white oil as raw materials.Subsequently,the mechanical and flowing properties of SEBS/PP/Fillers composite materials were evaluated.The influence of two fillers on the properties of composite materials were studied respectively.The best physical and mechanical properties of composite materials were made when talc power was modified by the combination of ND-201 with KH550(mass ratio was 0.25phr:0.25phr)and further used as the fillers.4.The microstructure and fracture morphology of SEBS/PP/Fillers composite materials were measured on a polarized light microscopy and scanning electron microscopy.The filler talcum powders dispersed uniformly in the composite materials when the filler content was less than 15 phr(mass ratio).And then the mechanical properities of composite materials improved.When the filler content was more than 15 phr(mass ratio),the filler talcum powders dispersed heterogeneously in composite materials and some agglomeration appeared in the composite matrix,which resulting in the decreasing of the mechanical properties of composite materials.The best content of talcum powders was chosen as 15 phr(mass ratio).5.The effects of the talcum powders content on the thermal properties of SEBS/PP/Fillers composite materials were discussed.The thermal stability of composite materials increased gradually with the addition of talc powders and their initial thermal decomposition temperature increased.The decomposition temperature of composite materials increased up to 10? when the content of talcum powders was 15 phr(mass ratio).6.The influence of talc powder on PP crystallization in SEBS/PP/fillers composite materials were evaluated by a differential scanning calorimetry(DSC)and X-ray diffraction(XRD).Experimental data indicated that the talc powders concentration has no effect of low temperature resistance on the composite.Talc powders was a nucleating agent and worked as a mechanism of heterogeneous nucleation in the crystallizing process,which increased the crystallinity of PP.However,talc powders did not change the crystalline of PP.