Study On Structure And Properties Of PP/POE/SiO₂ Composites With Ultrasonic Irradiation During Extrusion

In this paper, a polyolefin elastomer (POE) was selected to toughenpolypropylene (PP). The surface of nano-SiO₂ was modified with the couplingagent. The nano-SiO₂/PEA hybrids were prepared via emulsion polymerization.With the addition of the compatilizer (PP-g-MA), the PP/POE blends and thePP/POE/SiO₂ as well as PP/POE/PP-g-MA/SiO₂ composites were prepared duringextrusion under ultrasonic irradiation. The mechanical properties, crystallizationproperties and morphology of PP composites were studied and the rheologicalbehavior of PP/POE blends also was investigated. Through FTIR and XPS, thegrafting reaction of EA onto the surface of nano-SiO₂ for the nano-SiO₂/PEAhybrids was discussed.According to the results of the PP/POE blends under ultrasonic irradiation,the apparent viscosity of the PP/POE blends melt and the die pressure decreasewith increasing the ultrasonic intensity. The ultrasonic irradiation can enhance thecompatibility between PP and POE, reduce the size of POE particles and improvethe dispersion of POE in PP matrix. Appropriate ultrasonic irradiation and POEhave the synthetic effects on toughening PP. And the effects show moreremarkably before the brittle-ductile transition. Both POE and the ultrasonicirradiation control the crystallization behaviors of PP, and the addition of POE caninduce the formation ofβ-crystal. For the PP composites with nano-SiO₂ modified by the different treatments,appropriate ultrasonic irradiation can increase the izod-notched impact strengthand the elongation at break of the composites. The izod-notched impact strengthand the yield strength of the composites are further improved with the addition ofthe compatilizer whereas the elongation at break decreases. Compared with thePP/POE blends, the crystallization temperature of PP/POE/SiO₂ composites isincreased. The addition of the compatilizer further improves the crystallizationtemperature of PP/POE/SiO₂ composites. The melting peak ofβ-crystal occurs inDSC curves for PP/POE/SiO₂ composites with nano-SiO₂ modified with KH-550and NDZ-201. With adding the compatilizer, the melting peak ofβ-crystaldisappears. The spherulite size of PP is reduced and the spherulite is fined withthe addition of nano-SiO₂. The introduction of ultrasonic irradiation or thecompatilizer can strengthen this effect.Ethyl acrylate can be grafted successfully onto the surface of the pretreatednano-SiO₂ via emulsion polymerization and the nano-SiO₂/PEA hybrids preparedare used to modify the PP/POE blends. The izod-notched impact strength and thepeak intensity ofβ-crystal in DSC curves for PP/POE/SiO₂ compsoties reach themaximum value with 4wt% SiO₂. The dispersion of the nano-SiO₂/PEA hybrids inPP/POE/SiO₂ composites is better than that of SiO₂ treated with the couplingagent.