Abstract
Novel, fully biobased shape memory thermoplastic vulcanizates (TPVs) were prepared using two sustainable biopolymers, poly(lactic acid) (PLA), and modified natural Eucommia ulmoides gum (EUG-g-GMA), via a dynamic vulcanization technique. Simultaneously, in situ compatibilization was achieved in the TPVs to improve interfacial adhesion and the crosslinked modified Eucommia ulmoides gum (EUG) was in “netlike” continuous state in the PLA matrix to form “sea-sea” phase structure. The promoted interface and co-continuous structure played critical roles in enhancing shape memory capacity and toughness of the TPVs. The TPV with 40 wt % modified EUG displayed the highest toughness with an impact strength of 54.8 kJ/m2 and the most excellent shape memory performances with a shape fixity ratio (Rf) of 99.83% and a shape recovery ratio (Rr) of 93.74%. The prepared shape memory TPVs would open up great potential applications in biobased shape memory materials for smart medical devices.
Highlights
Given that Eucommia ulmoides gum (EUG) is less compatible with poly(lactic acid) (PLA), we modified EUG to introduce polar groups via the bulk radical grafting reaction of glycidyl methacrylate (GMA) monomer
The torque increased abruptly after the addition of Dicumyl peroxide (DCP), which might be attributed to the formation of EUG-GMA grafts and PGMA by self-polymerization of the GMA
GMA) was compatible with PLA, and a novel fully biobased shape memory thermoplastic vulcanizates (TPVs) were fabricated on the two biopolymers using a dynamic vulcanization technique
Summary
Shape memory polymers (SMPs), a class of smart materials, have attracted much attention from academia and industry because they are able to change their shapes in response to environmental stimuli, such as heat [1], light [2], electricity [3], moisture [4,5], pH values [6], and magnetic fields [3]. Changing the two parts in TPVs or altering their phase structure would result in tailored shape memory performances. It is essential to improve the compatibility of the two components and achieve a co-continuous phase structure for promoting the shape memory capacity of TPVs. Poly(lactic acid) (PLA), a kind of sustainable and degradable biopolymer, has been reported to exhibit HSME, inherent brittleness limited its application [31,32]. EUG is less compatible with PLA due to its non-polar molecular chains The modified EUG was used with PLA to develop a new-typed shape memory TPVs with co-continuous phase structure, improved interface, and super toughness via an in situ dynamic vulcanization method. TPVs would provide a new idea for the industrialization of smart materials
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