Study On Property Enhancement Of Ethylene-α-olefin Copolymer Thermoplastic Elastomers

In order to improving the processability,strength and service temperature of the ethylene-α-olefin copolymer (POE), POE / polystyrene (PS),POE / poly (styrene-b-ethylene-co-butylene-b-styrene) (SEBS),POE/PS/SEBS and POE / reclaimed isobutyleneisoprene rubber (RIIR) blends were prepared via melt blending respectively. The mechanical and rheological properties and crystalline behaviour of the blends were studied. Scanning electron microscopy (SEM) and transmission electron microcopy (TEM) were also used to observe and analyze the phase dispersion of each blend. The key works and conclusions were listed as follows::POE/PS blend is an immiscible system, with an increasing weight fraction of PS the morphology of PS phase is changed from an uniform spherical particle to coarse claval structure and the crystallinity of POE decreases, which induce the tensile strength of the blend decreases. But the melt apparent viscosity of POE reduces due the addition of PS, indicating that the processability of POE elastomer is improved. The melt apparent viscosity of POE doesn't decrease obviously when the weight fraction of PS up to 25%. Due to the formation of interpenetrating physical crosslinking network between POE and SEBS, the tensile strength and dynamic storage modulus in high temperature zone of POE/SEBS blends increase with the increasing weight fraction of SEBS in blends. These mean the POE is reinforced by the addition of SEBS. The crystallizing point and crystallinity of POE both decrease with the incorporation of SEBS. When the weight fraction of SEBS exceed to 30%, the dynamic complex viscosities of POE/SEBS blends change from negative to positive deviation. This is related to the formation of order netwok structure between the phase of POE and SEBS. Unfortunately, the processability of POE/SEBS is bader than POE.SEBS was proved to be efficient compatibilizers in blends of POE/PS. During melting blend, it is localized at the interface of POE and PS, improving the dispersion of PS particle, enhancing interfacial adhesion between the two phases. It can act as "bridge" to transfer stress. Consequently, the mechanical properties of the blend are improved. For POE/PS (75/25) blend, the analysis results of SEM and dynamic rheological properties show that the interfacial compatibilizer is saturated for SEBS content of about 25 phr. Superfluous SEBS is shown to form a third phase in POE. The micrographs obtained by TEM show that there exist SEBS encapsulates PS droplets,SEBS aggregate which diameter less than 100nm and interpenetrating and diffusion between POE and SEBS phase in the POE/PS/SEBS (60/10/30) blend. Dynamic mechanical and rheological properties analysis show the interaction among POE,PS,SEBS. DMA also shows that the storage modulus of POE at high temperature is reinforced by the addition of PS and SEBS, as a result, the service temperature of POE is improved. A synergistic reinforcement of PS and SEBS in tensile strength of POE was found in the POE/PS/SEBS (60/10/30) blendThe POE/RIIR (66.7/33.3) behave as thermoplastic elastomers properties. The compatibility between POE and RIIR is good, and the phase structure of that is two interpenetrating co-continue phases. Crosslinking structure is formed in RIIR phase after dynamic vulcanization which induces the mechanical properties of TPE are improved. The hardness of TPE can be adjusted by the addition of softening oil effectively. At the same time, the processability of TPE is improved. Carbon black has obvious reinforcing effect on TPE. The comprehensive mechanical properties of POE/RIIR TPE with POE 66.7 phr were good at 0.5 -1.0 phr sulfur, 20 phr oil, and 30 phr CB are excellent, respectively. The results of dynamic rheological properties show that the complex viscosities of POE/RIIR is higher than that of POE, which means that there exist some effect between molecular chain of POE and RIIR. Compared with POE/RIIR, the slope of terminational zone increases with the addition of softening oil and crosslinking agent, indicating the interacting effect is improved.