Glycerolysis of Poly(lactic acid) as a Way to Extend the “Life Cycle” of This Material (original) (raw)
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HYDROLYSIS AND BIODEGRADATION OF POLY(LACTIC ACID)
Advances in Polymer Science, 2018
In this work, a review is presented concerning hydrolytic degradation and biodegradation of Poly(lactic acid) (PLA). Hydro- lytic degradation, that induces morphological and compositional changes, is considered the most important step in determining the bio-degradation. The main factors influencing the hydrolytic degra- dation, such for instance temperature, pH, sample morphology, mo- lecular weight, are considered and analyzed. An overview on the bi- odegradation in composting conditions is also reported. Finally, the chapter analyses also the possibilities of modulating degradation and biodegradation rates in function of the expected lifetime of the ob- jects made in PLA. This can be considered a frontier of research in this field.
Towards sustainability of lactic acid and poly-lactic acid polymers production
Renewable & Sustainable Energy Reviews, 2019
Lactic acid (LA) is a platform chemical which can be produced biotechnologically on agricultural residues, wastes and by-products and further used for production of biodegradable, biocompatible LA polymers. These polymers are mostly used for high-end applications but they have potential for much wider application with decrease in production costs. Available technologies and strategies are reviewed in order to point out the issues, challenges and solutions relevant to increase sustainability and competitiveness of LA production on agricultural residues and wastes. Data on chemical composition, regional and seasonal availability of agricultural residues, wastes and by-products are lacking to provide predictable and effective combining for LA production. Precision agriculture, remote sensing and integration with data on chemical composition can help in better planning and more adequate exploitation of available sources in future. Novel pretreatments for the most abundant lignocellulosic feedstocks, which allow utilization of carbohydrates in LA production and side streams like lignin in other biorefineries are needed. Integration of pretreatment, hydrolysis and fermentation under non-sterile conditions or open fermentation mode should enable easier scale up and decrease energy consumption and costs without sacrificing LA purity. Capital investments in improvement of the available technologies are high. Support from policy makers stimulating production of LA polymers from second and third generation feedstocks will help in research, development and faster adoption on larger scale. For production of LA polymers with tailored properties, it is essential to choose the most productive method for LA production and separation from these complex substrates. The shift in research interest from LA polymerization towards "green" processing of LA polymers products is occurring and that will be the additional driving force for the field in future. Among renewable biomass, 3700 Mt of agricultural residues are produced in the world per annum [3] and around 440 Mt in EU [4]. Primary residues are generated in the fields and secondary are generated during processing of crops [4,5]. A certain amount of primary residues like straw is left at the field for fertilization and recovery of carbon to the soil, depending on crop, region, soil quality and agrotechnical measures applied [4,6]. Remaining primary residues together with secondary residues from sugar refineries, oil extraction, biofuels, starch or gluten production, grain milling etc. can be environmentally harmful and a treatment is needed to reduce or eliminate their negative effect. Usually, they are only partially valorised through anaerobic
Polymers
The predicted growth in plastic demand and the targets for global CO2 emission reductions require a transition to replace fossil-based feedstock for polymers and a transition to close- loop recyclable, and in some cases to, biodegradable polymers. The global crisis in terms of plastic littering will furthermore force a transition towards materials that will not linger in nature but will degrade over time in case they inadvertently end up in nature. Efficient systems for studying polymer (bio)degradation are therefore required. In this research, the Respicond parallel respirometer was applied to polyester degradation studies. Two poly(lactic-co-glycolic acid) copolyesters (PLGA12/88 and PLGA6/94) were tested and shown to mineralise faster than cellulose over 53 days at 25 °C in soil: 37% biodegradation for PLGA12/88, 53% for PLGA6/94, and 30% for cellulose. The corresponding monomers mineralised much faster than the polymers. The methodology presented in this article makes (bio)degra...
–Thermal treatment of 2.5 grams (dry weight) and 7.5 grams (dry weight) batches of Polylactic acid (PLA)-product waste was carried out at 121 oC and 160 oC and exposed to different treatment time periods. Molecular weight reduction was not affected by the amount of PLA material loaded. Rate of molecular weight reduction was about six times faster at 160 oC than at 121 oC. Complete depolymerization of the PLA-product waste was not possible at the temperatures used here. A maximum recovery (yield) of lactic acid of 35% was obtained at a loading of 7.5 g, temperature at 121 °C and exposure time of 720 min. At 160°C , recovery was 25% but obtained within 120 minutes. Results suggest that PLA-product waste behaviour will differ from pure PLA pellet. With PLA-product waste complete lactic acid recovery was not possible and other by-products like acetic and propionic acids were produced from thermal treatment. Keywords—Steam hydrolysis, PLA, first order kinetics, lactic acid Digital Object Identifier (DOI): Abstract–Thermal treatment of 2.5 grams (dry weight) and 7.5 grams (dry weight) batches of Polylactic acid (PLA)-product waste was carried out at 121 o C and 160 o C and exposed to different treatment time periods. Molecular weight reduction was not affected by the amount of PLA material loaded. Rate of molecular weight reduction was about six times faster at 160 o C than at 121 o C. Complete depolymerization of the PLA-product waste was not possible at the temperatures used here. A maximum recovery (yield) of lactic acid of 35% was obtained at a loading of 7.5 g, temperature at 121 °C and exposure time of 720 min. At 160°C , recovery was 25% but obtained within 120 minutes. Results suggest that PLA-product waste behaviour will differ from pure PLA pellet. With PLA-product waste complete lactic acid recovery was not possible and other by-products like acetic and propionic acids were produced from thermal treatment.
Polymer Degradation and Stability, 2008
The hydrolytic degradation of poly(L-lactide) (PLLA) and the formation of its monomer in the solid and in the melt were investigated at 120-150 C (in the solid), at 160 C (in the solid up to 40 min and in the melt exceeding 40 min), and at 170-190 C (in the melt). Such state difference caused the difference in the degradation behavior of PLLA and the behavior of lactic acid formation, although the degradation of PLLA proceeds via a bulk erosion mechanism, regardless of its state. The crystalline residues were formed at the degradation temperatures below 140 C, but not at the degradation temperatures above 160 C. The lactic acid yield exceeding 95% can be successfully attained for all the temperatures of 120-190 C. The activation energy for hydrolytic degradation values of PLLA were 69.6 and 49.6 kJ mol À1 for the temperature ranges of 120-160 C (in the solid) and 170-250 C (in the melt), respectively, and are compared with the reported values.
Towards Controlled Degradation of Poly(lactic) Acid in Technical Applications
C
Environmental issues urge for the substitution of petrochemical-based raw materials with more environmentally friendly sources. The biggest advantages of PLA over non-biodegradable plastics are that it can be produced from natural sources (e.g., corn or sugarcane), and at the end of its lifetime it can be returned to the soil by being composted with microorganisms. PLA can easily substitute petroleum-based plastics in a wide range of applications in many commodity products, such as disposable tableware, packaging, films, and agricultural twines, partially contributing to limiting plastic waste accumulation. Unfortunately, the complete replacement of fossil fuel-based plastics such as polyethylene (PE) or poly(ethylene terephthalate) (PET) by PLA is hindered by its higher cost, and, more importantly, slower degradation as compared to other degradable polymers. Thus, to make PLA more commercially attractive, ways to accelerate its degradation are actively sought. Many good reviews dea...
Study on Effect of Degradation of Poly(lactic acid) on its Properties
The publications of the MultiScience - XXXI. MicroCAD International Scientific Conference, 2017
In this study, the degradation of Polylactic acid and its impact on their properties were analyzed using different characterization techniques. The biological and thermal degradation of PLA was carried out in different climatic conditions for a period of 3 to 8 months. All the degraded samples were mechanically characterized using the universal materials testing machine. The chemical modification occurring on the surface of the PLA samples was examined with the help of FTIR-ATR spectroscopy. The morphological changes due to the degradation were determined by Differential Scanning Calorimetry (DSC) method.
Steam treatment of waste Polylactid acid (PLA) based products for lactic acid recovery
–Thermal treatment of 2.5 grams (dry weight) and 7.5 grams (dry weight) batches of Polylactic acid (PLA)-product waste was carried out at 121 o C and 160 o C and exposed to different treatment time periods. Molecular weight reduction was not affected by the amount of PLA material loaded. Rate of molecular weight reduction was about six times faster at 160 o C than at 121 o C. Complete depolymerization of the PLA-product waste was not possible at the temperatures used here. A maximum recovery (yield) of lactic acid of 35% was obtained at a loading of 7.5 g, temperature at 121 °C and exposure time of 720 min. At 160°C , recovery was 25% but obtained within 120 minutes. Results suggest that PLA-product waste behaviour will differ from pure PLA pellet. With PLA-product waste complete lactic acid recovery was not possible and other by-products like acetic and propionic acids were produced from thermal treatment.
Poly (lactic acid) Degradation Study
In his paper the degradation study of polylactic acid in soil at room temperature was studied to know the effect of microorganism present in domestic compost. Reduction in molecular weight studied by by Gel Permeation Chromatrography (GPC) from 75000 to 22400. Differential Scanning Calorimetry (DSC) was investigated. Through the investigation by DSC showed changes in melting temperature from 171 degree centigrade to 162 degree centigrade which confirmed decrease in crystalline nature and degradation of polylactic acid. Scanning Electron Microscopy (SEM) results showed that formation of small pores on the surface of Polylactic acid (PLA) which supports GPC, DSC data for degradation of PLA