PLA maleation: an easy and effective method to modify the properties of PLA/PCL immiscible blends

Abstract

In this study, maleic-anhydride-grafted polylactide (PLA-g-MA) was investigated as a potential compatibilizing agent for the polylactide (PLA)/poly(ε-caprolactone) (PCL) system, with the aim of enhancing the final properties of the two polymer blends. Indeed, PLA-g-MA was prepared via reactive blending through a free radical process and characterized by means of 1 H-NMR and titration measurements, which demonstrated that the employed procedure allows grafting 0.7 wt% of MA onto the polymer backbone, while avoiding a dramatic reduction of PLA molecular mass. The specific effect of the MA-grafted PLA on the features of the PLA/PCL system was highlighted by adding different amounts of PLA-g-MA to 70:30 (w/w) PLA/PCL blends, where the 70 % PLA component was progressively substituted by its maleated modification. The efficiency of PLA-g-MA as a compatibilizer for the PLA/PCL blends was assessed through SEM analysis, which showed that the dimensions of PCL domains decrease and their adhesion to PLA improves by increasing the amount of PLA-g-MA in the blends. The peculiar microstructure promoted by the presence of PLA-g-MA was found to enhance the mechanical properties of the blend, improving the elongation at break without decreasing its Young's modulus. Our study demonstrated that not only the microstructure but also the thermal properties of the blends were significantly affected by the replacement of PLA with PLA-g-MA.

Dynamics of partially miscible polylactide-poly(ε-caprolactone) blends in the presence of cold crystallization

“…1, which is also in agreement with previous studies (Castillo et al 2010;Dell'Erba et al 2001;Gardella et al 2014;Harada et al 2008;López-Rodríguez et al 2006). In order to explain this kinetic enhancement, the limited miscibility of PCL and PLA chains was suggested as the underlying mechanism (Sakai et al 2009;Zhang et al 2013).…”

“…The close solubility parameters of PCL and PLA, 9.2 and 10.1 (cal/cm 3 ) 1/2 , respectively (Coleman et al 1990), and the lack of specific interactions between PCL and PLA leads to partial miscibility of their blends (López-Rodríguez et al 2006). The miscibility of PLA/PCL blends can be enhanced by using compatibilizers, which modify the interfacial properties either chemically or physically (Castillo et al 2010;Gardella et al 2014;Harada et al 2008;Salehiyan and Hyun 2013;Shin 2013;Tuba et al 2011). The compatibilized blends have shown better mechanical properties such as elongation at break and impact resilient compared to virgin PLA.…”

“…Interestingly, blends of PLA/PCL have shown enhanced cold crystallization kinetics within the PLA phase, which cannot be explained trivially unless the blends are considered miscible (Castillo et al 2010;Dell'Erba et al 2001;Gardella et al 2014;Harada et al 2008;López-Rodríguez et al 2006;Wu et al 2011). In the compatibilized blend of PLA/PCL, the enhancement in cold crystallization within PLA phase is attributed to the increased PLA chain mobility imposed by miscible PCL chains at temperatures higher than the PCL melting temperature (Castillo et al 2010;Gardella et al 2014;Harada et al 2008;Tuba et al 2011;Wu et al 2011). Surprisingly, an increase in PLA nuclei density was observed during cold crystallization for immiscible/noncompatibilized blends of PLA/PCL.…”

Phase structure evolution during mixing and processing of poly(lactic acid)/polycaprolactone (PLA/PCL) blends

“…However, this improvement is limited by the low compatibility of PLA/PCL blends. Therefore, efficient compatibilizer for PLA/PCL blends has been intensively asked [28][29][30][31]. Less care has been paid to study effect of the properties of the component, and mixing and processing conditions on the morphology of PLA/PCL blends [32].…”

Reactive extrusion of bio-based polymer blends and composites – Current trends and future developments

“…Gardella et al [93] proposed the maleic anhydride grafted poly(lactic acid) (PLA-g-MA) as effective compatibilizer of PLA/PCL blends. It was found that replacing of PLA by PLA-g-MA reduced dimensions of the PCL domain and enhanced their adhesion to PLA, which have beneficial impact on the mechanical properties (increasing the elongation at break without deterioration of Young's modulus) of PLA/ PCL blends.…”