There are around 100,000 tons of PET bottles consumed every year in Taiwan. Green shirt made of recycled PET in Taiwan is a world-renowned products. However, the other green product made of recycled PET (rPET) is not so popular in the market as compared with recycled PP or PE product. Due to PET's rigid and tough engineering plastic property, PET is very suitable for high-valued sandwich -structured rigid foam core material. The rPET is not easy to manufacture high-valued foam core materials, because of low molecular weight of rPET, the high concentration of terminal functional groups -COOH and -OH in the molecular structure, and the poor physical properties of rPET. This project would develop extrusion foaming grade rPET formula with long-chain branch structure to meet the functional requirements of the extrusion foaming process through the combination of linear chain extension and chain branching reaction based on the molecular design concept. The rPET green foam core material could be applied to various areas of application: green high-energy-saving building, aerospace, wind energy turbines, lightweight new energy vehicles and other related high value-added markets. This project would build a mass production platform for rPET high-valued sandwich-structure foam composite in three years. In the first year, we will establish the core research and development capability of rPET green foam core material, and develop the flame retardant grade rPET green foam core material in the second year. In the third year, we will develop the high-valued sandwich-structure composite with the rPET green foam core material. The rPET green foam core material is recyclable, that means it can be managed in the traditional rPET recycling process. This project would introduce the upgrading rPET recycling process which the economic incentives would not only boost rPET recovery efficiency, but also widen the recycled PET product in the market. We hope to implement the upgrading rPET recycling process and it’s mission of circular economy. We have achieved two research products：extrusion foaming grade rPET material and 10cmX1cm rPET foam board with specific gravity of 0.175 via using linear chain extension and side chain branch structure modification technology to modified rPET. The extrusion foaming grade rPET rPET material has the following indicators: MI (g/10min@260℃, 1.2kg) increased from 34.4 to 12.8, torque increased from 4.3Nm to 7.7Nm, die swell ratio increased from 0.94 to 1.73, die head pressure increased from 18bar to 65bar. We propose to use die swell ratio and die head pressure increase as acceptable quality criteria for extrusion foaming grade rPET material. We can easily get low density rPET foam with specific gravity of 0.102~0.158 for extrusion foaming grade rPET material, as compared with 0.384~0.582 for rPET material.

Polyethylene terephthalate, reactive extrusion foaming, core material