Thanawadee Leejarkpai

Biodegradable kinetics of plastics under controlled composting conditions.

This study models and evaluates the kinetics of C-CO(2) evolution during biodegradation of plastic materials including Polyethylene (PE), PE/starch blend (PE/starch), microcrystalline cellulose (MCE), and Polylactic acid (PLA). The aerobic biodegradation under controlled composting conditions was monitorated according to ISO 14855-1, 2004. The kinetics model was based on first order reaction in series with a flat lag phase. A non-linear regression technique was used to analyze the experimental data. SEM studies of the morphology of the samples before and after biodegradation testing were used to confirm the biodegradability of plastics and the accuracy of the model. The work showed that MCE and PLA produced the high amounts of C-CO(2) evolution, which gave readily hydrolysable carbon values of 55.49% and 40.17%, respectively with readily hydrolysis rates of 0.338 day(-1) and 0.025 day(-1), respectively. Whereas, a lower amount of C-CO(2) evolution was found in PE/starch, which had a high concentration of moderately hydrolysable carbon of 97.74% and a moderate hydrolysis rate of 0.00098 day(-1). The mineralization rate of PLA was 0.500 day(-1) as a lag phase was observed at the beginning of the biodegradability test. No lag phase was observed in the biodegradability testing of the PE/starch and MCE. The mineralization rates of the PE/starch and MCE were found to be 1.000 day(-1), and 1.234 day(-1), respectively. No C-CO(2) evolution was observed during biodegradability testing of PE, which was used for reference as a non-biodegradable plastics sample.

Compostability and Ecotoxicity of Poly(lactic acid) and Starch Blends

This paper revealed the compostability of poly (lactic acid) (PLA) and PLA/starch blends with various amounts of starch contents. The results showed that the ultimate aerobic biodegradation under controlled composting conditions of PLA and PLA/starch with 30, 50 and 70 wt% starch contents were 83.43%, 84.28%, 88.04% and 95.83%, respectively. Under the same testing conditions, the biodegradation of cellulose, as a positive material, was 84.89%. In the disintegration testing, the tested materials were completely biodegraded and no residuals were observed through visual inspection after 30 days. In ecotoxicity test, the rate of germination and plant growth of monocotyledon and dicotyledon on the resulting compost were no significant different when compared to blank compost under. It can be concluded that the PLA and PLA/starch blends were clearly safe for the ecosystem. Furthermore, these materials were biodegradable and compostable materials as they pass all requirements of ISO 17088.

Biodegradable Compatibilized Poly(l-lactide)/Thermoplastic Polyurethane Blends: Design, Preparation and Property Testing

Biodegradable blends of poly(l-lactide) (PLL) toughened with a polycaprolactone-based thermoplastic polyurethane (TPU) elastomer and compatibilized with a purpose-designed poly(l-lactide-co-caprolactone) (PLLCL) copolymer were prepared. Both 2-component (PLL/TPU) and 3-component (PLL/TPU/PLLCL) blends of various compositions were prepared by melt mixing, hot-pressed into thin films and their properties tested. The results showed that, although the TPU could toughen the PLL, the blends were immiscible leading to phase separation with the TPU domains distributed in the PLL matrix. However, addition of the PLLCL copolymer could partially compatibilize the blend by improving the interfacial adhesion between the two phases. Biodegradability testing showed that the blends were biodegradable and that the PLLCL copolymer could increase the rate of biodegradation under controlled composting conditions. The 3-component blend of composition PLL/TPU/PLLCL = 90/10/10 parts by weight was found to exhibit the best all-round properties.

Poly(Lactic Acid)/Poly(Butylene Succinate) Blends Filled with Epoxy Functionalised Polymeric Chain Extender

In this work, biodegradable plastics were produced from different poly(lactic acid) (PLA)/ poly(butylene succinate) (PBS) blend ratios in the presence of a fix loading (1 phr) of a commercial epoxy functionalised polymeric chain extender (Joncryl ADR-4300-S). The effects of blend ratio and chain extender on the tensile properties, thermal stability and morphology were investigated by the tensile testing, thermogravimetric analysis (TGA) and scanning electron microscopy, respectively. The results show that the incorporation of PBS and Joncryl into PLA apparently reduced the tensile strength and tensile modulus, but increased the elongation at break of the blends in a dose-dependent manner. However, their blends provide interesting materials for industrial packaging applications, due to their enhanced ductility by decreasing the tensile modulus and increasing the elongation at break. TGA analysis showed that thermal stability of the blends was lower than that of the pure PLA and PBS. Moreover, the chain-extended products exhibit two stages of thermal decomposition, the first was due to the degradation of PBS, and the second was due to the degradation of PLA.

Comparative Study of the Bio-Disintegration Behavior of Polylactic Acid under Laboratory and Pilot-Scale Composting Conditions

In recent years, compostable plastics have gained a great attention as green materials due to the problems of more plastic waste generated each year over the world. One attractive of compostable plastics is that after use they can be biodegraded by natural microorganisms in the composting process within a specified period of time. Degree and rate of disintegration during composting is an important requirement that is used to determine the compostability of these plastics. This research work studied and compared the disintegration behaviors of PLA laboratory and pilot-scale composting conditions according to ISO 20200:2004 and ISO 16929:2002. Finally, the results from the disintegration testing could be used to evaluate the compostability, biological properties and impacted of a plastic material on the fermentation of organic waste in the composting plant.

Assessment of Greenhouse Gas (GHG) Emissions of Polylactic Acid (PLA)/Starch and Polyethylene Terephthalate (PET) Trays

This study aims to assess greenhouse gas (GHG) emissions of Poy(lactic acid) (PLA) with cassava starch blend (PLA/starch) and Poly(ethylene terephthalate) (PET) trays from cradle to grave. The various waste treatment scenarios were considered. The functional unit is specified as 10,000 units of 8 x 10 x 2.5 cm. of PLA/starch and PET trays which weigh 597.6 and 582.7.5 kilograms, respectively. The results from cradle to production gate were found that GHG emissions of PLA/starch has 51.38% lower than that of PET. This is because PET has higher weight of the trays. The resin production stage of PET tray has the highest of greenhouse GHG emissions. The results from cradle to grave show that the highest total GHG emissions are observed from PLA/starch or PET trays with 90% of landfill and 10% of incineration. The lowest GHG emissions from disposal PLA/starch and PET trays are from landfill with biogas recovery and incineration with heat recovery. This can be reduced GHG emissions by 3.11103 and 1.28103 kg CO2 equivalent.

The Ultimate Biodegradation of the Starch Based Biodegradable Plastics

The objective of this work was to investigate the ultimate aerobic biodegradation of poly (lactic acid) (PLA) and poly (butylene adipate-co-terephthalate) (PBAT), with and without the starch according to ISO14855-1: 2004. The degree of biodegradation for 120 days of PLA, PLA/starch (50:50), PBAT and PBAT/starch (50:50) were 85.75%, 93.60%, 23.71% and 73.32%, respectively. The degree of biodegradation of cellulose was 70.20% under the same conditions. For PLA, a lag phase was observed during the first twenty days of the testing. This result indicated that there was no ultimate biodegradation occurred at the beginning of testing period of PLA. However, no lag phase was observed in the biodegrability testing of the PLA/starch (50:50), PBAT and PBAT/starch (50:50). Moreover, the addition of starch into the polymers leads to higher biodegradation rate of the materials. Finally, the biodegradation results were confirmed by thermal gravimetric analysis (TGA), fourier transform infrared spectroscopy (FT-IR) and scanning electron microscope (SEM). It was found that the results of TGA, FT-IR and SEM were in good accordance with the biodegradation results.

Study of the Disintegration of Poly (butylene adipate-co-terephthalate) and Starch Co-Extruded Materials

The disintegration behavior of biodegraded plastics materials including poly (butylene adipate-co-terephthalate) (Ecoflex), Ecoflex/starch blend, poly (butylene adipate-co-terephthalate) (Enpol) and Enpol/starch blend in controlled composting was described. The blends were compounded using a twin screw extruder with co-rotating mixing screw. The aerobic disintegration tests were carried out in the reactors under constant temperature at 58 + 2 °C for 90 days. During testing moisture, mixing and aeration of the samples were periodically determined and controlled according to ISO 20200:2004. The results showed that the percentage of disintegration of Ecoflex, Ecoflex/starch blend (50:50 %wt.), Enpol and Enpol/starch blend (50:50 %wt.) were 25.91%, 80.57%, 56.29% and 91.08%, respectively. It was also found that starch content facilitate the disintegration of the polymers. The morphologies and thermal properties of the residues were studied using SEM and TGA. It was found that the surface morphologies and the thermal properties results are in accordance with the biodisintegration degree.

Use of Microcrystalline Cellulose Prepared from Cotton Fabric Waste to Prepare Poly(butylene succinate) Composites

The mechanical properties, thermal behaviors and morphology of poly(butylene succinate) (PBS)/microcrystalline cellulose (MCC) composites were investigated. The MCC used in this study was prepared by hydrolyzing cotton fabric waste with 2.5 N hydrochloric acid at 100°C for 30 min. PBS was melt mixed with three loading of MCC (10, 20 and 30 wt%) in an internal mixer, followed by compression molding into 0.3-mm sheet. The effects of MCC on the tensile properties, thermal stability, crystallization and morphology were investigated using the Instron testing machine, thermogravimetric analyzer, differential scanning calorimeter and scanning electron microscope, respectively. The incorporation of MCC into PBS results in a significant increase in the Young’s modulus but a decrease in the tensile strength and elongation at break. Moreover, the thermal degradation of the composites was not improved after introducing MCC into PBS. It was also found that, the MCC did not affect the melting temperature, but induced a slight increase in the crystallization temperature of the composites. The SEM micrographs show brittle fracture surfaces of the composites where the pull out MCC particles and pull out holes were observed.