Biodegradation of Polylactic Acid and Starch Composites in Compost and Soil Article Information (original) (raw)
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Biodegradation of Polyactic Acid and starch composites in compost and soil
2018
Dyfyniad o'r fersiwn a gyhoeddwyd / Citation for published version (APA): Wilfred, O., Tai, H., Marriott, R., Liu, Q., Tverezovskiy, V., Curling, S., Fan, Z., & Wang, W. (2018). Biodegradation of Polyactic Acid and starch composites in compost and soil. International Journal of Nano Research, 1(2), 1-11. https://innovationinfo.org/internationaljournal-of-nano-research/article/Biodegradation-of-Polylactic-Acid-and-Starch-Composites-inCompost-and-Soil
Soil Biodegradation of a Blend of Cassava Starch and Polylactic Acid
Ingeniería e Investigación
This study evaluated bio-based blended films produced from polylactic acid (PLA) and thermoplastic starch (TPS) under soil conditions for four weeks (W). The degradation of the film was evaluated in addition to thermal, structural, and morphological changes on the surface of the material. There were evident structural changes; the TPS present in the film degraded from weeks 0 to 4, exhibiting a loss of mass between 350 and 365 °C in the TGA test. This behavior was attributed to the condensation of hydroxyl groups of the cassava starch as well as to a loss of mass corresponding to the degradation of PLA between 340 and 350 °C. The addition of TPS in the PLA-containing matrix resulted in a decrease in the Tg of the PLA/TPS blends. The increase in crystallinity improved the water vapor permeability in the structure. Consequently, the incorporation of starch in these blends not only reduces the cost of the material, but it also contributes to its rapid biodegradation (68%). These result...
Biodegradation of starch/polylactic acid/poly(hydroxyester-ether) composite bars in soil
Polymer Degradation and Stability, 2003
Injection molded tensile bars composed of native corn starch (0-70%), poly(d,l-lactic acid) (95% L) (PLA, 13-100%) and poly(hydroxyester-ether) (PHEE, 0-27%) were buried in soil for 1 year in order to study the effects of starch and PHEE on rates of biodegradation. Rates of weight loss increased in the order pure PLA ($0%/year) < starch/PLA (0-15%/year) < starch/PHEE/ PLA (4-50%/year) and increased with increasing starch and PHEE contents. Weight losses were due to starch only with the degradation proceeding from outside to inside along a narrow zone. Tensile strength did not change with time for pure PLA and, after an initial decline, did not change much for the other compositions. Some formulations containing PHEE and lower (40%) starch levels had higher tensile strengths after initial exposure to soil than those without PHEE.
Identification of important abiotic and biotic factors in the biodegradation of poly(l-lactic acid)
International Journal of Biological Macromolecules, 2014
The biodegradation of four poly(l-lactic acid) (PLA) samples with molecular weights (MW) ranging from approximately 34 to 160kgmol(-1) was investigated under composting conditions. The biodegradation rate decreased, and initial retardation was discernible in parallel with the increasing MW of the polymer. Furthermore, the specific surface area of the polymer sample was identified as the important factor accelerating biodegradation. Microbial community compositions and dynamics during the biodegradation of different PLA were monitored by temperature gradient gel electrophoresis, and were found to be virtually identical for all PLA materials and independent of MW. A specific PLA degrading bacteria was isolated and tentatively designated Thermopolyspora flexuosa FTPLA. The addition of a limited amount of low MW PLA did not accelerate the biodegradation of high MW PLA, suggesting that the process is not limited to the number of specific degraders and/or the induction of specific enzymes. In parallel, abiotic hydrolysis was investigated for the same set of samples and their courses found to be quasi-identical with the biodegradation of all four PLA samples investigated. This suggests that the abiotic hydrolysis represented a rate limiting step in the biodegradation process and the organisms present were not able to accelerate depolymerization significantly by the action of their enzymes.
Discarded polymer materials are one of the causes of environmental pollution, leading to develop biodegradable materials, such as polymer composites. One commercial biodegradable polymer, called EcobrasTM, is claimed to be a good alternative in this respect, particularly because it is made with raw materials from renewable sources. Green coconut rush fiber is a lignocellulosic material, with low cost because it is a large scale waste. This article reports the preparation of new composites of EcobrasTM and green coconut rush fiber and the study of their biodegradation in simulated soil, revealing the microorganisms presence on the surface of the composites. The test consists in burying the samples in the soil for different periods, following the ASTM G 160-03 standard. After each interval, the samples were removed from the soil and analyzed by scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and Fourier-transform infrared spectroscopy (FTIR). According to the results, EcobrasTM and its composites with green coconut rush fiber were considered biodegradable materials, and microorganisms presence on the material surface was observed. We expect these results will enable the development of biodegradable composites that will minimize the environmental impact generated by the inappropriate disposal of polymer materials.
Biodegradation of Treated Polylactic Acid (PLA) under Anaerobic Conditions
Transactions of the ASABE, 2009
Biodegradation of untreated and treated thermoformed polymer polylactic acid (PLA) under anaerobic conditions was investigated. Treatments consisted of subjecting PLA to irradiation (gamma source and e-beam) and steam (120°C for 3 h). Absorbed doses were 72 and 172 kGy for gamma-irradiated samples and 72, 144, and 216 kGy for e-beam irradiated samples. Methods to assess biodegradation were weight loss of irradiated PLA and biochemical methane potential (BMP) of steam-treated PLA during anaerobic digestion at mesophilic (37°C) and thermophilic (58°C) conditions. Untreated PLA degraded only at thermophilic conditions. Treated PLA degraded at both conditions and was more sensitive to biodegradation, showing greater weight loss and methane yield. The order of effectiveness of treatments from greatest to lowest was steam exposure, gamma irradiation, and e-beam irradiation. Under thermophilic conditions, gamma-irradiated PLA lost 45% of its weight in 180 days, and steam-treated PLA produced methane at 225 cc CH 4 per gram in 56 days. The most significant finding of this work is that PLA degrades under anaerobic thermophilic conditions, suggesting that post-consumer PLA material may be used in anaerobic digestion for energy recovery, instead of being treated as waste disposal.
Degradation Behaviors of Different Blends of Polylactic Acid Buried in Soil
Energy Procedia, 2013
Polylactic acid (PLA), as the biodegradable polymer becomes more attention as a green material for industrial applications. Lipase-catalysed polymerization with Lecitase Ultra and Lipozyme TL IM were applied to synthesize PLA to decrease the chemical-catalysts utilization which having toxicity interferes in products. PLA products were characterized by end group/HPLC analyses for M n /M n n w determination. The results indicated that low molecular weight PLA could be successfully produced from commercial lactic acid by using the commercial lipases. With using Lipozyme TL IM as biocatalyst, obtainable M n and M w of PLA were 7,933 Da and 194 Da, respectively. For Lecitase Ultra used as biocatalyst obtainable M n and M w of PLA were 8,330 Da and 216 Da, respectively. Subsequently, the resulting PLA products from this method were prepared as PLA films blended with commercial PLA beads varying the blending ratios by casting on glass plate. Their degradable behaviors were studied under controlled soil burial laboratory conditions. The characteristics of PLA blend films were analyzed using visual observations, measuring weight loss, DSC and FTIR analysis. The results observed that the different blends ratios of PLA films showed more flexible than pure PLA film. Besides, the different blends of PLA films were disintegrated in soil within the short burial time.
Waste management (New York, N.Y.), 2011
The biodegradability and the biodegradation rate of two kinds biodegradable polymers; poly(caprolactone) (PCL)-starch blend and poly(butylene succinate) (PBS), were investigated under both aerobic and anaerobic conditions. PCL-starch blend was easily degraded, with 88% biodegradability in 44 days under aerobic conditions, and showed a biodegradation rate of 0.07 day(-1), whereas the biodegradability of PBS was only 31% in 80 days under the same conditions, with a biodegradation rate of 0.01 day(-1). Anaerobic bacteria degraded well PCL-starch blend (i.e., 83% biodegradability for 139 days); however, its biodegradation rate was relatively slow (6.1 mL CH(4)/g-VS day) compared to that of cellulose (13.5 mL CH(4)/g-VS day), which was used as a reference material. The PBS was barely degraded under anaerobic conditions, with only 2% biodegradability in 100 days. These results were consistent with the visual changes and FE-SEM images of the two biodegradable polymers after the landfill bu...
2000
Poly(l-lactide) (PLLA) was rapidly (bio)degraded by a mixed culture of compost microorganisms. After 5 weeks in biotic environment, the films had fragmented to fine powder, while the films in corresponding abiotic medium still looked intact. Analysis of the low molecular weight products by GC-MS showed that microorganisms rapidly assimilated lactic acid and lactoyl lactic acid from the films. At the same time, a new degradation product, ethyl ester of lactoyl lactic acid was formed in the biotic environment. This product cannot be formed by abiotic hydrolysis and it was not detected in the abiotic medium. The degradation of the PLLA matrix was monitored by differential scanning calorimetry (DSC), size exclusion chromatography (SEC) and scanning electron microscopy (SEM). A rapid molecular weight decrease and increasing polydispersity was observed in the biotic environment. In the abiotic environment only a slight molecular weight decrease was seen and the polydispersity started decreasing towards 2.0. This indicates different degradation mechanisms, i.e. preferred degradation near the chain ends in the biotic environment and a random hydrolysis of the ester bonds in the abiotic environment. SEM micrographs showed the formation of patterns and cracks on the surface of the films aged in biotic medium, while the surface of the sterile films remained smooth. The SEM micrographs showed a large number of bacteria and mycelium of fungi growing on the surface of the biotically aged films.