甲基乙烯基硅橡胶(MVQ)具有良好的电绝缘性和耐高温性能,广泛应用于高压电缆附件,但其热导率偏低、热稳定性有限,在高热负荷下易产生热积聚。为改善MVQ的热学性能,采用分子动力学构建纯MVQ及纳米ZrO2质量分数为4.5%、9%、12%和15%的复合体系分子模型,研究40～400K(K=℃+273.15)范围内模型的热学行为及微观结构演化。结果表明,随着纳米ZrO2含量增加,体系玻璃化转变温度升高,热膨胀系数减小,纳米ZrO2质量分数为15%的复合体系在360K条件下的热导率较纯MVQ提高19.01%。自由体积分数、均方位移和回转半径均随纳米ZrO2含量增加而降低,表明自由体积被压缩、链段运动受限、分子链趋于紧凑;结合能增大,界面作用增强。热学参数与上述微观参数相互印证,从分子尺度说明纳米ZrO2通过压缩自由体积并强化界面约束改善MVQ的热稳定性和导热性能,可为高温电缆附件材料设计提供参考。
Methyl vinyl silicone rubber (MVQ) possesses good electrical insulation and high-temperature resistance,making it widely used in high-voltage cable accessories.However,its intrinsically low thermal conductivity and limited thermal stability tend to cause heat accumulation under high thermal load.To improve its thermal performance,molecular dynamics simulations were employed to construct pure MVQ and MVQ/ZrO2 composite models with nano-ZrO2 contents of 4.5%,9%,12% and 15%.Their thermal behavior and microstructural evolution in the temperature range of 40-400 K were investigated.The results showed that with increasing nano-ZrO2 content,the glass transition temperature (Tg) of the system increased while the coefficient of thermal expansion decreased,and the thermal conductivity of the 15% composite at 360 K increased by 19.01% compared with pure MVQ.The free volume fraction,mean-square displacement (MSD) and radius of gyration (Rg) all decreased with the increase of filler content,indicating compressed free volume,restricted chain mobility and more compact chain conformations,while the absolute value of the interaction energy increased,reflecting enhanced interfacial interactions between ZrO2 and MVQ.The thermal parameters and these microstructural descriptors were mutually consistent,demonstrating at the molecular scale that nano-ZrO2 improved the thermal stability and thermal conductivity of MVQ mainly by compressing the free volume and strengthening interfacial constraints,which could provide a reference for the design of high-temperature cable accessory materials.
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基金资助
国家自然科学基金(51577105)
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