The Blending of Poly(glycolic acid) with Polycaprolactone and Poly(l-lactide): Promising Combinations.

Luca Magazzini,Sara Grilli,Seif Eddine Fenni,Orietta Monticelli,Alessandro Donetti,Dario Cavallo

doi:10.3390/polym13162780

Luca Magazzini, Sara Grilli + Show 4 more

Open Access

https://doi.org/10.3390/polym13162780

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Journal: Polymers	Publication Date: Aug 18, 2021
Citations: 27	License type: CC BY 4.0

Affiliation: University of Genoa, World Wide Fund for Nature

Abstract

Poly(glycolic acid) (PGA) holds unique properties, including high gas barrier properties, high tensile strength, high resistance to common organic solvents, high heat distortion temperature, high stiffness, as well as fast biodegradability and compostability. Nevertheless, this polymer has not been exploited at a large scale due to its relatively high production cost. As such, the combination of PGA with other bioplastics on one hand could reduce the material final cost and on the other disclose new properties while maintaining its “green” features. With this in mind, in this work, PGA was combined with two of the most widely applied bioplastics, namely poly(l-lactide) (PLLA) and poycaprolactone (PCL), using the melt blending technique, which is an easily scalable method. FE-SEM measurements demonstrated the formation of PGA domains whose dimensions depended on the polymer matrix and which turned out to decrease by diminishing the PGA content in the mixture. Although there was scarce compatibility between the blend components, interestingly, PGA was found to affect both the thermal properties and the degradation behavior of the polymer matrices. In particular, concerning the latter property, the presence of PGA in the blends turned out to accelerate the hydrolysis process, particularly in the case of the PLLA-based systems.

Highlights

The concerns about the accumulating plastic waste pollution as well as the increasing environmental pressure on global warming have stimulated tremendous attention toward bioplastics [1,2,3]
Blends show a typical sea-island morphology, where the spherical domains of poly(glycolic acid) (PGA) are dispersed in the PLLA matrix, demonstrating, at least for the analyzed compositions, the immiscibility between the two phases
Considering the dimensions of the PGA domains in the system PLLA/PGA (Figure 2), it is worth underling that their average diameter tends to decrease significantly, reducing the amount of the polymer in the blend, passing from 14 μm in the case of PLLA70/PGA30 sample to 5 μm for the blend PLLA90/PGA10

Summary

Introduction

The concerns about the accumulating plastic waste pollution as well as the increasing environmental pressure on global warming have stimulated tremendous attention toward bioplastics [1,2,3]. The polymer chains, which have a similar chemical structure to poly(lactic acid) (PLA) but without the methyl side group, are tightly packed together, producing elevated thermal stability and high degree of crystallinity [4] The latter unique feature, which affects the PGA properties, was studied in detail. Due to its highly crystalline structure, PGA has the strongest mechanical strength but the lowest fracture toughness in comparison to PLA, polylactic-co-glycolic acid (PLGA), and polyethylene terephthalate (PET) [4] Another interesting feature of the polymer, which affects its extent of hydrolysis, is the relatively high hydrophilicity compared to other biopolymers, such as PLA and PCL [13,14,15,16]. As occurs for other polyesters, the degradation rate is accelerated by the increase in the carboxylic end groups during the decomposition [17]

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