Hydrolysis of polylactide in aqueous media

Abstract

In this study, two commercial polylactide (PLA) grades with different d‐lactate contents were subjected to hydrolysis in neutral, acidic, and alkaline aqueous media at temperatures above the glass transition. We monitored the hydrolysis process by means of tracking the changes in the molecular weight distribution, weight loss, water uptake, and PLA crystallinity as a function of time. In both, neutral and acidic media, hydrolysis showed an initial induction period over which no weight loss was observed, whereas the average molecular weight dropped drastically. After this initial period, the weight loss increased rapidly, whereas the molecular weight decreased slowly. Additionally, in alkaline media, hydrolysis occurred mainly through a surface‐erosion process; this resulted in a simultaneous molecular weight decrease and weight loss without a noticeable induction period. An autocatalytic mechanism was assumed in neutral and acidic media to describe the hydrolysis kinetics. The measured molecular weight decrease over time was successfully described by a two‐stage exponential model. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44152.

A new approach for flexible PBAT/PLA/CaCO3 films into agriculture

“…The lower polymer chains may be removed from the polymer surface, allowing the biotic process to begin with microorganisms absorb these low M w chains and complete the decomposition of the material. As the hydrolysis is strictly related to water absorption, the lower values of degradation of the samples are associated to the better compatibility in the polymer matrix and to the high orientated amorphous structures, which reduces the free spaces leading to small rates of hydrolysis and consequently reduces degradation rates . The results agrees with outer results, as reported by Palsikowski et al .…”

“…Table shows the mass variation behavior for 360 days, period when they were inserted into the simulated soil. In the initial phase, the mass of all samples slightly increased, as expected, due to the water absorption on it . However, after the analyzed period, the samples did not present an expressive mass reduction (with only a slight reduction observed after 270 days).…”

“…In these photomicrographs, it can be observed the formation of fractures in the surface, a specific effect of superficial erosion, defining the beginning of PLA and PBAT degradation . The surface erosion, as reported by Rodriguez et al . is one of the main effects of polymer hydrolysis.…”

Hydrolytic stability of polylactide and poly(methyl methacrylate) blends

“…Several studies have investigated the kinetics of PLA hydrolysis . Based on our previous work, an exponential model of the drop in molecular weight over time can be successfully described by two‐stage: where M n 01 is the molecular weight prior to hydrolysis, M n 02 is the molecular weight intercept of the second hydrolysis stage, k 1 as well as k 2 are the kinetic constants for each stage, and t P is the time where the shift occurs between the two stages. The first stage, was called the induction period and was characterized by a dramatic drop in molecular weight without any weight loss.…”

“…found for thin amorphous PLA films in an alkaline medium that the crystallinity increased only by 8% after 150 days. At higher temperatures, above T g , it was found that PLA crystallinity increases to its maximum level within 24 h …”