Poly(lactic acid) (PLA), the polymer object of this study, degrades by a biotic process after an abiotic hydrolysis process. Its degradation was evaluated after 600 days of exposure in a simulated marine environment (SME), as buriti fiber-reinforced composites having triacetin as coupling agent. Composites were obtained by extrusion and films were produced by compression molding. After between 60 and 600 days of exposure, PLA had a weight loss of 2.5%, PLA/T of 1.5%, and 10-12% of weight loss for PLA/B and PLA/B/T, respectively. PLA intercalates reduction, increase, and decrease of its crystallinity attributed to hydrolysis (up to 15 days), impairment of amorphous segments (45 days), and loss of integrity of the matrix (100-600 days), respectively. In the PLA/T composites, triacetin inhibited the diatom colonization process, having its crystallinity values increased after nearly 100 days of exposure with subsequent reduction. For samples with buriti fiber, changes in crystallinity were attributed to absorption of water and exposure of matrix amorphous segments. PLA degradation in a SME is evidently favored by the use of natural fibers since they make easier water access to the matrix and colonization by the protists group, diatoms, showing that the polymer can have reduced postuse shelf life as composites, with benefits while in use and at the same time post-use environmental benefits. Triacetin inhibits PLA colonization and degradation up to 45 days after exposure, after which it no longer influences the degradation process. V C 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43290.

Small pieces of diseased tissue were surface sterilized with 0·5% NaOCl, plated on 2% potato dextrose agar (PDA) at pH 6, and incubated at 22 to 24 ° C. Dense, whitish mycelium developed within 72-96 h. Microconidia were abundant, globose to piriform, 0-1 septate, 4 -10 × 4·5-7 μ m, and formed on unbranched and branched monophialides. Cultures produced a fruity aroma similar to amyl acetate. Spores from 14-day-old colonies that developed on PDA were removed with 4 mL of sterile water. The pathogenicity of the fungus was tested by spraying five healthy inflorescences of tomato with a 5-mL suspension (2 × 10 5 conidia mL -1 of sterile distilled water). Another five healthy inflorescences were sprayed with sterile distilled water. The plants were placed in a growth chamber with a 12-h photoperiod at 22 ± 2 ° C and covered with polyethylene bags that were removed after 3 days when plants were moved to a glasshouse. While control flowers were healthy, all inoculated flowers showed symptoms similar to those observed previously.

This work examined the influence of different chemical blowing agents (CBA), one endothermic and one exothermic, at the same concentration (2% by mass), on poly(acid lactic), PLA foams. The CBA was incorporated into the PLA in a single-screw extruder, and the foams were expanded by heating in an electric oven under free pressure conditions. Foam degradation in a simulated soil was performed according to the ASTM G160-03 standard. Changes in the physical-chemical, morphological and mechanical properties were used to evaluate the degradation. The results indicated that the different chemical blowing agents led to different mechanical and morphological properties for the foams, which resulted from the nature and decomposition rate of the blowing agents. Cells in the foams accelerated the degradation since they facilitated the infiltration of water toward the interior of the polymer and triggered the degradation process by hydrolysis.

The use of biodegradable polymers has aroused academic and technological interest directed to the replacement of conventional polymers aiming at reducing the environmental impact caused by these materials. Vegetable fibres as reinforcement elements provide gains in mechanical, thermal and degradation properties to polymer composites. The buriti fibre (Mauritia flexuosa) is an abundant crop of easy cultivation in tropical countries and its use in composites with poly(lactic acid) (PLA), can provide the development of a material with specific features, combining good mechanical properties and excellent degradation potential to the obtained composites. In this research, PLA and buriti fibre composites were developed with the use of triacetin as coupling agent. For a 30% content by mass of fibre, the results showed that the mechanical properties of the composites were similar to those of neat PLA. This was attributed to the fibre/matrix interaction observed by the SEM analysis and to an increase in crystallinity assessed by thermal properties.