Biobased Poly(lactide)/ethylene-co-vinyl Acetate Thermoplastic Vulcanizates: Morphology Evolution, Superior Properties, and Partial Degradability

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• 作者：Piming Ma ; Pengwu Xu ; Yinghao Zhai ; Weifu Dong ; Yong Zhang ; Mingqing Chen
• 刊名：ACS Sustainable Chemistry & Engineering
• 出版年：2015
• 出版时间：September 8, 2015
• 年：2015
• 卷：3
• 期：9
• 页码：2211-2219
• 全文大小：655K
• ISSN：2168-0485

文摘

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 (畏_PLA/畏_EVA) that resulted in a novel morphology evolution of the TPV, i.e., from sea鈥搃sland-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 (畏*), elasticity (G鈥? and the solid-like behavior of the PLA/EVA-based TPV. Meanwhile, superior tensile strength (蟽_t = 21 MPa), low tensile set (T_s = 30%), moderate elongation (蔚_b = 200%) and suitable stiffness (E鈥?= 350 MPa, 25 掳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 掳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.