Abstract
This paper presents a biodegradation study conducted for 90 days under standardized controlled composting conditions of poly (lactic acid) (PLA) filled with functionalized anatase-titania nanofiller (PLA/TiO2 nanocomposites). The surface morphology, thermal properties, percentage of biodegradation, and molecular weight changes at different incubation times were evaluated via visual inspection, scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and gel permeation chromatography (GPC) by taking degraded samples from compost at the end of target biodegradation time interval. The rapid increase of crystallinity indicated that the PLA and PLA/TiO2 nanocomposites had heterogeneous degradation mechanisms under controlled composting conditions. The biodegradation rate of PLA/TiO2 nanocomposites was higher than that of pure PLA because water molecules easily penetrated the nanocomposites. The dispersion of the nanoparticles in the PLA/TiO2 nanocomposites affected the biodegradation rate of PLA. Moreover, the biodegradation of PLA could be controlled by adding an amount of dispersed TiO2 nanofillers under controlled composting conditions.
Highlights
(lactic acid) (PLA), a synthetic biodegradable polymer, is investigated worldwide for biomedical and consumer applications because of the increasing need for renewable materials that are sustainable alternatives to petrochemical-derived products [1–4]
The temporal changes in the appearance of the pure PLA and PLA/TiO2 nanocomposites were different under laboratory conditions
The pure PLA matrix surfaces, which were initially transparent in agreement with the amorphous structure, became relatively whitish after 2 days of biodegradation [41]
Summary
(lactic acid) (PLA), a synthetic biodegradable polymer, is investigated worldwide for biomedical and consumer applications because of the increasing need for renewable materials that are sustainable alternatives to petrochemical-derived products [1–4]. PLA is the product that results from the polymerization of lactide or lactic acid, which is the most extensively produced carboxylic acid in nature by microbial fermentation of carbohydrates [5]. The biodegradation of PLA in composting conditions, a temperature- and humidity-dependent process, involves several processes, namely, water uptake, ester cleavage, and formation and dissolution of oligomer fragments [26]. The heat and moisture in the compost attack the PLA chains and split them apart, thereby producing small Mw polymers and, eventually, lactic acid. Thereafter, the microorganisms in the compost and soil mineralize the oligomer fragments and lactic acid to generate methane and carbon dioxide (CO2) under anaerobic and aerobic conditions, respectively [27–29]
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