Biodegradable plastics are thought to be the possible directions in managing plastic pollutions. Unfortunately, they are not recycled in most countries since they are designed to decompose even though recycling is a more pragmatic method than landfill or incineration. Thus, it is more constructive to develop methods to recycle biodegradable plastics or to develop biodegradable yet recyclable plastics. In this study, we used cutlery with a composite of poly(lactic acid) (PLA) and talc. The possibility to recycle it to make foams was studied even though it will have lowered mechanical strength from the recycling process as it is less significant for this product. Tensile properties of solid PLA and foams showed no significant decrease in the strength up to three processes of compression molding and foaming. We performed shear rheometry to determine the thermal stability and dependences of the complex viscosity on frequency and temperature. The magnitude of the complex viscosity dramatically increased with decreasing frequency and such an upturn increased with temperature, but time-temperature superposition was valid at high temperatures. The extensional rheometry showed no strain hardening, but physical foaming using supercritical carbon dioxide (CO 2 ) could still occur, and the operating conditions to obtain various foamed structures were determined. We also compared the effects of one-directional against three-dimensional expansion. Overall, the concentration of CO 2 in PLA and crystallinity of the foams are the two key variables to describe the bulkiness of foams. Surprisingly, the lower the CO 2 concentration, the bulkier the foams at any sorption temperature and pressure.

It is a concern that microplastics have been discovered in the food sources and water that we consume. This research was to evaluate the methods to isolate microplastics from organisms and how much of the environment of New Zealand (NZ), which is one of the least polluted countries, is contaminated by microplastics. New Zealand green-lipped mussels (Perna canaliculus) are considered to be an important product in the NZ food industry. For this reason, the existence of microplastics in these were investigated. Tarakihi fish (Nemadactylus macropterus) take food near the bottom of ocean, so this fish can be an indicator of the contamination of microplastics denser than water. In addition, bottled water, tap water and sea salt samples were also investigated. To isolate solid particles in an animal body, its tissues were chemically digested. It was found that 10% (w/w) potassium hydroxide (KOH) was a practical digestive protocol on biological tissues since polymers such as polyethylene terephthalate (PET), high-density polyethylene (HDPE), low-density polyethylene (LDPE), polypropylene (PP) and polystyrene (PS) are relatively resistant to KOH. Thus, treating tissues with KOH can be considered a viable method to remove tissues and isolate microplastics. Nile red was used to stain the plastic particles from the samples for visual inspection. Fourier-transform infrared spectrometry (FTIR) was performed to identify the particles. It was evaluated that all those samples had traces of microplastics.

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