| 英文摘要 |
PLA waste had grown up annually by more and more application at supermarket, for example the egg boxes and food trays. PLA was a low temperature resistance and low Izod impact polymer which could cause thermal decomposition easily at high temperature process. Therefore, PLA was very difficult to re-produce under traditional recycling process. Because PLA was one kind of polyester polymer so it could be reacted with glycol monomer to get polyester polyol. The polyol could react with COOH functional group to obtain polyester oligomer or polyester polymer. In addition, this polyol could also be reacted with different diisocynate to obtain the polyurethane product for coating and adhesive application, or to react with diiscyanate and foaming agent to produce the soft or rigid foamed product.
One important aim of this project was focused on the preparation of foamed materials from recycled PLA. In this studt, we had finished the investigation on the optimization of PLA glycosis reaction condition, including the reaction time, reaction temperature, glycol and its weight ratio, and catalyst. During the glycosis reaction, we tested the variation of polyol viscosity on the reaction time to judge the reaction rate and reaction endpoint. GPC analysis was applied to estimate the molecular weight (MW) and MW distribution. Another important aim of this project was to compare the RPLA flake glycosis condition with virgin PLA 2003D (V-PLA). Then, both of RPLA and V-PLA polyol were reacted with diisocynate monomer to get PU foamed product. In addition, for establishing the database of physical properties of recycled PLA, we separated the PLA waste stream into four different kinds, including cool drink cup, egg box, all kinds of RPLA sorted by NIR machine once, and all kinds of RPLA sorted by NIR machine twice. The recycled PLA plate container was putted into the processive lines, including crushing, cleaning, separation, and palletizing. Then, the obtained RPLA resin was used as the standard sample for injection. Comparing impact strength with these four kinds of RPLA resin, the results showed a downward trend, egg boxes>cups>NIR sorting twice>NIR sorting once. As the metal screen pressure raised, the operator needed to change the metal screen. For egg boxes and cups, they needed to change metal screen after operating for five hours. However, for the NIR sorting twice and once, the metal screen needed to be changed after operating only for thirty and twenty minutes, respectively. The present results showed that it was difficult to seprate mixed plate container efficiently and obtain the RPLA with a high purity, even using NIR sorting machine and water separation tank.
In summary, we concluded that the foamed material with a good foam density and pore size could be successfully prepared by using the polyester polyol obtained from recovered PLA, isocyanate, and foaming agents. Moreover, this foamed material was also used in the fabrication of wood and tile insulation and reinforcement materials. The finished product showed that the foamed material could be applied to heat insulation and material strength reinforcement applications.
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