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 are not easy to produce high-priced foam core materials. 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. This project intends to use various compounds containing P and N to synthesize copolyester, which has high compatibility with PET. This flame-retardant foaming grade PET, which char-forming effect is fast, that can effectively improve the flame retardant properties of the rPET; on the other hand, this new type of synthetic high phosphorus-containing polyester has a network structure, which can form a network branch with rPET, that can increase the melt strength of flame-retardant PET, and enhance the foamability of rPET.
This project uses combination of chain extenders and flame retardant modification technology to prepare three products: flame-retardant foaming grade rPET, 5cmx0.3cm flame retardant rPET foam sheet and sandwich-structure composite with the rPET green foam core material (rPET foam/rPET foam/rPET foam, PET fabric/rPET foam/PET fabric, aluminum/rPET foam/aluminum, carbon fiber/rPET foam/carbon fiber). We have developed flame-retardant foaming grade rPET formulation, rPET with 0.6% CE chain extender and 3% flame retardant, and 5cmx0.3cm flame retardant rPET foam sheet with specific gravity of 0.3~0.45, thickness of 3.3~4.8mm, and LOI>24, which can meet the requirements of the horizontal burning rate and flame resistance of the vehicle interior materials. Also PET fabric/rPET foam/PET fabric sandwich-structure composite material is a fully recycled rPET environmentally friendly product.