Preparation And Properties Of Thermoplastic Silicone Vulcanizate

Thermoplastic vulcanizate（TPV）is usually a high-performance thermoplastic elastomer prepared by dynamic vulcanization（DV）.Unlike traditional thermoplastic elastomer（TPE）and simple blends,TPV is composed of a low-content thermoplastic phase and a high-content crosslinked rubber phase,and rubber phases with extremely fine particle sizes can be uniformly dispersed in a continuous thermoplastic phase.This type of composite not only exhibits the high elasticity of the crosslinked rubber phase,but also shows the melt flowability and repeat processing properties of the thermoplastic phase.Due to the advantages of a high recovery rate and easy processing,TPV plays an important role in the circular economy,sustainable development,and other fields.TPV can be applied to various fields of production and life such as automobiles,medical equipment,mechanical parts,etc.With the continuous advancement of green environmental protection process and sustainable development,TPV with special structures and functions have been invented one after another.As the most eye-catching category,thermoplastic silicone vulcanizate（TPSi V）have attracted much attention due to their excellent high-temperature compressive resistance,low-temperature super toughness,hydrophobicity,stain resistance,chemical corrosion resistance,and silky tactility,and have gradually become a research hotspot for scientists.This article selects high-density polyethylene（HDPE）,ethylene-octene copolymer（POE）with excellent low-temperature performance,and polyamide 12（PA12）with excellent high-temperature resistance as the continuous phase.Methyl vinyl silicone（MVQ）is used as the dispersed phase to prepare thermoplastic silicone vulcanizates with excellent mechanical properties,elasticity,thermal stability,hydrophobicity,shape memory performance,and good repeat processing performance.The specific research content of this article is as follows:First,a series of HDPE/MVQ TPVs with excellent low-temperature toughness were prepared in this article.The influence of the blending ratio on TPVs’comprehensive performance was studied.The results showed that the notch impact strength of TPVs at-70℃reached 74.7 k J·m^-2,which was 313.5%higher than pure HDPE.In terms of shape memory and hydrophobicity,TPVs’shape fixity（R_f）and shape recovery ratio（R_r）reached 94.1%and 87.4%,respectively,with a maximum surface contact angle of 108.5°.On the basis of HDPE/MVQ TPVs,ceramic HDPE/MVQ TPVs with excellent flame retardancy were also prepared.The influence of zeolite content on the combustion performance,dimensional stability,flame retardant mechanism,and heat resistance of ceramic TPVs was studied in this article.The results showed that with the generation of Mg（Cl O₄）₂,Mg₃（Si₂O₅）（OH）₄,and Mg₃Cl B₇O₁₃ on the ceramicized surface of TPVs,the oxygen index（LOI）of TPVs could reach up to 31.5%,and the combustion rating was V-0.In the erosion experiment,the mass erosion rate of TPVs could be reduced to 0.0075 g/min,and the ceramic yield could reach up to 56.1%.Next,a series of POE/MVQ TPVs with excellent low-temperature resistance were prepared and the influence of the rubber-plastic blending ratio on the relevant properties of TPVs was studied in this paper.The results showed that the crosslinking density（CD）of these TPVs system increased with the increase of MVQ compounding rubber content.Meanwhile,the crystallinity（X_c）of the matrix material POE gradually decreased with the increase of MVQ compounding content.Under the dual influence of CD and X_c,the tensile strength of TPVs showed a trend of first increasing and then decreasing,with the maximum value of P₉M₁ being 30.1 MPa.The TPVs also exhibited excellent elasticity and low-temperature resistance,with a creep recovery rate of up to 80.9%at room temperature and an increase in notch impact strength from8.0 k J·m^-2 to 13.6 k J·m^-2 at-70℃.The TPVs prepared in this paper achieved a good combination of high strength,high elasticity,and low-temperature toughness.Finally,a series of PA12/MVQ TPVs with high-temperature resistance were prepared by introducing compatibilizers and coating techniques.The influence of the rubber-plastic blending ratio on the comprehensive performance of PA12/MVQ TPVs was studied in this manuscript.The results showed that the mechanical properties of PA12/POE-g-MAH/MVQ@POE TPVs prepared by in-situ compatibilization and coating technology were the most excellent,with the highest tensile strength,elongation at break,and notch impact strength reaching 35.2 MPa,264%,and 89.8k J·m^-2,respectively.Most importantly,with the increase in MVQ content and compatibility,the thermal conductivity and high-temperature resistance of TPVs also show an upward trend.In particular,compared to pure PA12,M-PA₆MP₄ has increased T₁₀,T₅₀,T₉₀,T_max,and carbon residue(R_C-y)by 16.0℃,19.6℃,7.9℃,23.5℃,and2.56%,respectively.