Mechanical and Shape Memory Properties of Poly(vinyl acetate)/Poly(lactic acid) Blends

Hypothesis: Shape memory polymers (SMPs) are intelligent materials that can be set into temporary shape and return to their permanent (original) shape when an external stimulus is applied. Poly(vinyl acetate) (PVAc) is a low cost biopolymer. However, its use in biomedical applications, especially as an SMP, is limited due to its low modulus and strength. On the other hand, poly(lactic acid) (PLA) is a biodegradable polymer with robust structure. Hence, blending of these two polymers can improve mechanical properties as well as shape memory behavior of PVAc.
a series of shape memory materials were prepared through blending of PVAc and PLA through solution mixing method using chloroform as solvent.
Findings: Microstructure of the prepared samples studied by X-ray diffraction spectroscopy (XRD) and atomic force microscopy (AFM), indicated that the components of the blends were favorably compatible. Moreover, dynamic mechanical thermal analysis (DMTA) and tensile test showed that the blending of these compatible biopolymers led to improvement in tensile strength and modulus of PVAc. Finally, the shape memory experiments revealed that the PVAc/PLA blends exhibited improved shape memory behavior as compared with their parent polymers. For instance, by incorporation of 30 wt% PLA into PVAc, the shape recovery increased from 75.4 to 91.5%. The improvement in the shape recovery was assigned to higher stored elastic energy in the blends as compared with that in neat polymers, which provided a larger driving force for corresponding quick and almost complete shape recovery. This procedure may open an avenue to fabricate SMPs through a simple blending method to be applied in different biomedical areas.