Shemao Wu

Novel heat and oil-resistant thermoplastic vulcanizates based on ethylene-vinyl acetate rubber/poly(vinylidene fluoride)

Thermoplastic vulcanizates (TPVs) combine the excellent elasticity of conventional vulcanized rubbers and the easy processability and recyclability of thermoplastics. In this study, we successfully prepared novel heat and oil-resistant TPVs based on ethylene-vinyl acetate rubber (EVM) and poly(vinylidene fluoride) (PVDF) by dynamic vulcanization (DV). The phase morphology, morphological evolution, and the properties of the EVM/PVDF TPVs were studied, and the microstructure–property relationship during DV was revealed. Interestingly, a large number of EVM rubber nanoparticles are observed in the EVM/PVDF TPVs during DV, and these nanoparticles assemble into oriented EVM fibers and EVM bundles during DV. As the DV further proceeds, the oriented EVM fibers and EVM bundles agglomerate with one another more densely and further assemble into EVM spherulites, leading to an increase in the thickness of the PVDF ligaments and the deterioration of the rubber network. More importantly, our EVM/PVDF TPVs show good mechanical properties, high elasticity, good processability, excellent heat-and oil resistance, and good recyclability. This study provides guidance for the preparation of new TPVs that can replace the traditional thermosetting rubbers in automotive and oil pipeline areas.

The influence of structure on thermomechanical and processing property of amorphous optical material

Abstract The influence of structure of poly(bisphenol-A carbonate) on property was systematically studied by both experiment and molecular dynamic simulation. At the molecular level, it was observed that copolymerisation of dichlorodimethylsilane did not improve the thermal stability and optical property, through 13C-nuclear magnetic resonance. Molecular simulation has good agreement with experimental results on density, half decomposition temperature (T1/2), glass transition temperature (Tg), refraction index, flow activation energy and mechanical performance. The molecular dynamics results demonstrated the feasibility of molecular simulation technique in designing materials at the molecular scale, and had advantage in improving our understanding of material’ performance and pressure–volume–temperature characteristics. The pressure–volume–temperature dependences of different microstructure amorphous were characterised to optimise the processing parameters, and to obtain accurate prediction of materials property. The empirical Tait equation of state well described the pressure–volume–temperature dependence of amorphous liquids.

A simulation study about the effects of temperature on the diffusion of oxygen in cis-1,4-polybutadiene

Abstract Three-dimensional periodic molecular models of amorphous cis-1,4-polybutadiene (cis-PBD) were constructed using the Materials Studio (MS)® software to study the effects of temperature on the diffusion of oxygen (O2). The radial distribution function, solubility parameter and others clearly proved the three-dimensional periodic molecular model was able to reproduce bulk experimental data of the authentic materials. The volume fraction of accessible oxygen was reckoned by fractional free volume with a probe radius of 1.8 Å. The diffusion coefficients (D) of O2 were calculated, and researches on the diffusion mechanism were made. Data obtained corresponded with the trend from available experiments and previously published simulation work. The results confirmed the accelerating effect of high temperatures on the diffusion of O2 and meanwhile suggested the favourable binding sites of thermo-oxidative aging reactions. Our findings have an important significance for promoting the development of membrane separation technology and provide valuable guidance for further research on thermo-oxidative aging of cis-PBD.