Fumi Ninomiya

Anaerobic Biodegradation Tests of Poly(lactic acid) under Mesophilic and Thermophilic Conditions Using a New Evaluation System for Methane Fermentation in Anaerobic Sludge

Anaerobic biodegradation tests of poly(lactic acid) (PLA) powder were done at the thermophilic (55 °C) and mesophilic temperature (35 °C) under aquatic conditions [total solid concentrations of the used sludge were 2.07% (at 55 °C) and 2.24% (at 35 °C)] using a newly developed evaluation system. With this system, the evolved biogas is collected in a gas sampling bag at atmospheric pressure. This method is more convenient than using a pressure transducer or inverted graduated cylinder submerged in water. PLA was degraded about 60% in 30 days, about 80% in 40 days and about 90% in 60 days at 55 °C. On the other hand, the PLA degradation started in 55 days at 35 °C and degradation rate was much slower than at 55 °C.

Biodegradability Evaluation of Polymers by ISO 14855-2

Biodegradabilities of polymers and their composites in a controlled compost were described. Polycaprolactone (PCL) and poly(lactic acid) (PLA) were employed as biodegradable polymers. Biodegradabilities of PCL and PLA samples in a controlled compost were measured using a Microbial Oxidative Degradation Analyzer (MODA) according to ISO 14855-2. Sample preparation method for biodegradation test according to ISO/DIS 10210 was also described. Effects of sizes and shapes of samples on biodegradability were studied. Reproducibility of biodegradation test of ISO 14855-2 by MODA was confirmed. Validity of sample preparation method for polymer pellets, polymer film, and polymer products of ISO/DIS 10210 for ISO 14855-2 was confirmed.

Biodegradation of Poly(butylene succinate) Powder in a Controlled Compost at 58 °C Evaluated by Naturally-Occurring Carbon 14 Amounts in Evolved CO2 Based on the ISO 14855-2 Method

The biodegradabilities of poly(butylene succinate) (PBS) powders in a controlled compost at 58 °C have been studied using a Microbial Oxidative Degradation Analyzer (MODA) based on the ISO 14855-2 method, entitled “Determination of the ultimate aerobic biodegradability of plastic materials under controlled composting conditions—Method by analysis of evolved carbon dioxide—Part 2: Gravimetric measurement of carbon dioxide evolved in a laboratory-scale test”. The evolved CO2 was trapped by an additional aqueous Ba(OH)2 solution. The trapped BaCO3 was transformed into graphite via a serial vaporization and reduction reaction using a gas-tight tube and vacuum manifold system. This graphite was analyzed by accelerated mass spectrometry (AMS) to determine the percent modern carbon [pMC (sample)] based on the 14C radiocarbon concentration. By using the theory that pMC (sample) was the sum of the pMC (compost) (109.87%) and pMC (PBS) (0%) as the respective ratio in the determined period, the CO2 (respiration) was calculated from only one reaction vessel. It was found that the biodegradabilities determined by the CO2 amount from PBS in the sample vessel were about 30% lower than those based on the ISO method. These differences between the ISO and AMS methods are caused by the fact that part of the carbons from PBS are changed into metabolites by the microorganisms in the compost, and not changed into CO2.

Highly Accelerated Aging Method for Poly(ethylene terephthalate) Film Using Xenon Lamp with Heating System

PET films were degraded at temperature higher than 100°C with steam and xenon light by using the newly developed system. Degradation products obtained using the proposed and conventional systems were essentially the same, as indicated by the similar increase in the intensity of the carbonyl peak near 1685 cm−1 in the FT-IR spectra of irradiated specimens and spectrum of original PET film. Elastic moduli derived from the stress-strain (SS) curves obtained in tensile tests were almost the same in the case of the proposed and conventional systems and were independent of the heating temperature, light intensity, and irradiation time. Tensile strength of degraded PET films decreases with increasing heating temperature. Tensile strengths of PET films degraded at same temperature decrease linearly with increasing intensity of xenon light. The lifetime at 90% strength of PET films was calculated. Attempts were made to express this lifetime as functions of the light intensity and the reciprocal of the absolute temperature by using the Eyring model. Estimated lifetime 15.9 h of tensile test using Eyring model for PET film agreed with the lifetime 22.7 h derived from data measured using the xenon weather meter.

Biobased carbon content of resin extracted from polyethylene composite by carbon-14 concentration measurements using accelerator mass spectrometry

An estimation procedure for biobased carbon content of polyethylene composite was studied using carbon-14 (14C) concentration ratios as measured by accelerated mass spectrometry (AMS). Prior to the measurement, additives and fillers in composites should be removed because they often contain a large amount of biobased carbon and may shift the estimation. Samples of resin with purity suitable for measurement were isolated from composites with a Soxhlet extractor using heated cyclohexanone. After cooling of extraction solutions, the resin was recovered as a fine semi-crystalline precipitate, which was easily filtered. Recovery rates were almost identical (99%), even for low-density polyethylene and linear low-density polyethylene, which may have lower crystallinity. This procedure could provide a suitable approach for estimation of biobased carbon content by AMS on the basis of the standard ASTM D 6866. The biobased carbon content for resin extracted from polyethylene composites allow for the calculation of biosynthetic polymer content, which is an indicator of mass percentage of the biobased plastic resin in the composite.

Round Robin Tests to Determine Fiber Content of Carbon Fiber-Reinforced Thermoplastic Composites by Combustion and Thermogravimetry

To propose methods to determine the fiber content of carbon fiber-reinforced plastics (CFRP) for the International Organization for Standardization, the fiber contents of CFRP with polyamide-6 were measured using a combustion method based on ISO 14127 and a thermogravimetry method based on the modified ISO 9924-3 under a round robin test managed by the Polymer Subcommittee of the Industrial Technology Cooperative Promotion Committee in Japan. In the combustion method, the fiber contents of the CFRTP (~0.3 g) were determined by the mass of carbon fiber remaining after burning (ISO 14127). The fiber contents in weight of the CFRTP with 8, 9, or 10 plies were determined to be 55.720%, 61.088%, or 65.326%, respectively, by 17 research institutes. In the thermogravimetry method, the fiber contents of the CFRTP (~10 mg) were determined by the mass of carbon fiber remaining after heating it to 600°C in nitrogen gas using thermogravimetry apparatus (modified ISO 9924-3). The fiber contents of the CFRTP with 8, 9, or 10 plies were determined to be 56.908%, 61.579%, or 64.819%, respectively, by 8 research institutes. It was confirmed that thermogravimetry method was as accurate as the combustion method based on ISO 14127.