Partially biobased thermoplastic vulcanizates (TPV) with novel morphology, superior properties and partial degradability were prepared by dynamic cross-link of saturated poly(lactide) and ethylene-co-vinyl acetate (PLA/EVA) blends using 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (AD) as a free radical initiator. EVA showed higher reactivity with free radicals in comparison with PLA, leading to much higher gel content of the EVA phase (G_f-EVA) than that of the PLA phase (G_f-PLA). However, the G_f-PLA increased more steeply at AD content larger than 1 wt % where the reaction of EVA approached to a saturation point. The competing reaction changed the viscosity ratio of the two components (η_PLA/η_EVA) that resulted in a novel morphology evolution of the TPV, i.e., from sea–island-type morphology to phase inversion via a dual-continuous network-like transition and finally cocontinuity again with increasing the AD content. The cross-link and phase inversion considerably enhanced the melt viscosity (η*), elasticity (G′) and the solid-like behavior of the PLA/EVA-based TPV. Meanwhile, superior tensile strength (σ_t = 21 MPa), low tensile set (T_s = 30%), moderate elongation (ε_b = 200%) and suitable stiffness (E′ = 350 MPa, 25 °C) were successfully achieved by tailoring the cross-link structure and phase morphology. In addition, the TPV are partially degradable in aqueous alkali. A degradation rate of approximately 5 wt % was achieved within 10 weeks at 25 °C and the degradation mechanism was investigated from both molecular and macroscopic levels. Therefore, this work provides a new type of partially biobased and degradable materials for substitution of traditional TPV.

中文翻译：

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生物基聚（丙交酯）/乙烯-共-乙酸乙烯酯热塑性硫化：形态演化，高级属性，局部降解

部分生物基热塑性硫化橡胶（TPV）具有新的形态，优良的性能和部分降解是由饱和的聚（丙交酯）和乙烯的动态交联制备的共（PLA / EVA）共混物使用2,5-二甲基-2 -乙酸乙烯酯，5-二（叔丁基过氧）己烷（AD）作为自由基引发剂。与PLA相比，EVA与自由基的反应性更高，从而导致EVA相（G _f-EVA）的凝胶含量远高于PLA相（G _f-PLA）的凝胶含量。但是，G _f-PLA当EVA的反应达到饱和点时，当AD含量大于1 wt％时，其上升更为陡峭。竞争反应改变了两种组分的粘度比（η _PLA /η _EVA），其通过双连续网络状过渡导致TPV，即一种新的形态的演变，从海岛型形态相转化最后，随着广告内容的增加，再次具有连续性。交联和相转化大大提高了基于PLA / EVA的TPV的熔体粘度（η*），弹性（G '）和类似固体的行为。同时，优异的拉伸强度（σ_吨= 21兆帕），低拉伸形变（Ť_小号= 30％），中度伸长率（ε _b= 200％）和合适的刚度（E '= 350 MPa，25°C）是通过调整交联结构和相形态成功实现的。另外，TPV在碱水溶液中可部分降解。在25°C下，在10周内达到了约5 wt％的降解率，并从分子和宏观水平研究了降解机理。因此，这项工作提供了一种新型的部分生物基的可降解材料来替代传统的TPV。