Study On Properties Of Nano-Silica/Elastomer/Polypropylene Composites And The Relationship Between Mechanical Properties And Sub-Cluster Parameters

The modification to general-purpose polymer such as Polypropylenehas been a prior research field for many years. Polypropylene has somedefects such as low notch impact strength and toughness which limit itsapplication. There have been a lot of researches carried out in the world inthese years, in which the applications of elastomers and nano inorganicmaterials are most remarkable. In this paper, we used nano-Silica and POE as stiff and elasticparticles respectively to modify PP by melt-blending process in order to getthe concerted toughening effect and good overall mechanic properties. Thereinforcing and toughing effects were studied by the test of the mechanicalproperties, DSC, as well as morphology of cross-sections. In this paper, nano-silica/PP composite and nano-silica/elastomer/PP III北 京 化 工 大 学 硕 士 学 位 论 文composite were studied respectively. The study of the mechanicalproperties of nano-silica/PP composite showed that nano-silica had thetoughening effect to PP. The tensile strength and modulus changed little.Then we added POE and ESI elastomer separately to the blend andcompared their effects. Results showed that the two elastomers bothincreased the impact strength linearly. However, POE had more remarkabletoughening effect in the range of allowable ratios(≤100/15). The tensilestrength and modulus of POE blends were also higher than ESI blends ateach ratio. So POE was the perfect elastomer. Study of crystallization and melting properties of blends showed thatNano-Silica had the nucleation effect to PP. It increased the crystallizationtemperature and crystallization rate of PP. It was presumed that nano-silicamade the PP spherocrystal smaller, which improved the mechanicalproperties. POE reduced the crystallinity of PP and increased thecrystallization temperature slightly. Both nano-silica and POE didn't affectthe melting point of PP. SEM photographs of cross-sections showed the nano-silica and POEdispersed evenly in PP matrix. Nano-silica appeared as particle aggregateswhose sizes were equal to the nano-silica offspring and didn't aggregatemore in melt-blending process. Nano-silica particles' size was smaller thancritical size. It absorbed the energy and inhibited the diffusion of crackswhen materials were impacted. So the toughness was improved. POE IV北 京 化 工 大 学 硕 士 学 位 论 文appeared as smooth and round particle and its shape didn't change incomposites. The two particles closed to and acted on each other, then hadthe concerted toughening effect. Basing on above research results, JRG Sub-cluster statistics theorywas first used to explain the relationship between the microstructures andproperties of PP/nano-silica/POE blend system. The content of nano-silicaaffected the distribution of POE in composites. By studying the quantitativerelationship of the impact strength and R1, R2 of POE, we could make thisconclusion: with the increase of R1 ? R2 value, the impact strengthdecreased, which implied that the relationship between the impact strengthand sub-scaling of the blend submitted to the maximum energy principle.