Tuning the dual- and triple-shape-memory effect of thermoplastic polyurethane/polylactic acid/poly(propylene carbonate) ternary blends via morphology control

• Published in: Polymer (Guilford) 2022-03, Vol.242, p.124546, Article 124546
• Main Authors: Zeng, Bingbing, Cao, Meiyu, Shen, Jiabin, Yang, Keke, Zheng, Yu, Guo, Shaoyun
• Format: Article
• Language: English
• Subjects: Co-continuous structure; Direct melting; Dual- and triple-shape-memory effect; Heat treating; Melt blending; Morphology; Morphology control; Polylactic acid; Polymer blends; Polymers; Polyurethane; Polyurethane resins; Propylene; Recovery; Shape effects; Shape memory; Spreading coefficient; Surface tension; Switches; Ternary blend; Urethane thermoplastic elastomers
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2022.124546

In this work, the ternary shape-memory blends consisting of thermoplastic polyurethane (TPU), polylactic acid (PLA), and poly(propylene carbonate) (PPC) were prepared via direct melt blending. Due to the different compatibility, viscosity and surface tension, PLA and PPC coalesce into a compound phase (LPC) and then assembled with TPU to form a special co-continuous structure in each blend as the mass ratio of TPU and LPC fixed at 50:50, which was first predicted based on the spreading coefficient theory and then confirmed by SEM observation. Moreover, the morphology of PLA and PPC serving as switches and the interfacial area between TPU and LPC can be tailored through simply adjusting the composition of LPC, leading to the tunable dual- and triple-shape-memory effects (DSME and TSME). For DSME via regarding the whole LPC as the single switch, both the shape fixation and recovery ratios decline with decreasing the PLA content. It is revealed that replacing PLA with PPC not only weakens the mechanical support from LPC for holding temporary deformation but also reduces the interfacial area and thus the driving effect from TPU for shape recovery. When PLA and PPC respectively act as the switch to memorize the two temporary shapes, TSME can be realized and the property governed by phase morphology exhibits diverse variation trends at the different stages. By comparison, the blend containing 15 wt% PLA showed the best TSME, which was characterized both qualitatively and quantitatively. The simplicity of this strategy in fabricating polymeric materials with tunable multiple-shape-memory performances implies the scalability to other polymer pairs. [Display omitted] •Morphology control enables the formation of co-continuous structure in ternary blends.•Prediction of morphological structure based on the spreading coefficient theory.•Phase morphology and interfacial area could be tailored by a simply variation of mass ratio.•Tunable dual- and triple-shape memory effects were realized.•The operative shape-memory mechanism was systematically discussed.