Plasticized polyvinyl chloride (PVC) gel is a type of electroactive polymers, which has potentials to be applied as soft actuators. However, few studies have been performed to investigate the mechanical responses of PVC gels in cyclic loading conditions. In this work, we combined experiments and theory to characterize the mechanical responses of two plasticized PVC gels. The gels were subjected to different types of loading-unloading-reloading cycles. The experimental results showed that the plasticized PVC gels exhibited stress softening response (the Mullins effect) in the cyclic tests. Meanwhile, the gels regained some strength after annealing at room temperature for several hours, indicating the self-healing ability of gels. We further extended the eight-chain model with incorporation of the chain dissociation and reassociation mechanism. The developed constitutive model is able to reproduce the Mullins effect and the recovery of the Mullins effect observed in the experiments. Our results clearly show that understanding the complex mechanical response is crucial for the applications of plasticized PVC gels.

增塑的聚氯乙烯（PVC）凝胶是一种电活性聚合物，具有用作软促动器的潜力。但是，很少有研究来研究在循环负载条件下PVC凝胶的机械响应。在这项工作中，我们结合了实验和理论来表征两种增塑的PVC凝胶的机械响应。凝胶经受不同类型的加载-卸载-重新加载循环。实验结果表明，增塑的PVC凝胶在循环测试中表现出应力软化响应（Mullins效应）。同时，凝胶在室温下退火数小时后恢复了一定的强度，表明凝胶的自我修复能力。我们通过结合链解离和重结合机制进一步扩展了八链模型。建立的本构模型能够重现穆林斯效应，并在实验中观察到穆林斯效应的恢复。我们的结果清楚地表明，了解复杂的机械响应对于增塑PVC凝胶的应用至关重要。