Polymerization of ethylene terephthalate cyclic oligomers with a cyclic dibutyltin initiator

To produce high-performance poly(ethylene terephthalate) (PET) composites f rom the polymerization of ethylene terephthalate cyclic oligomers (ETCs) pr epared From PET waste, the viscosity, thermal stability, and crystallizatio n of ETC melts were investigated, and ETC melt was; polymerized with cyclic dibutyltin initiator (cyclic stannoxane 1). The melt viscosity of ETCs at 295 degrees C where all ETCs can be melted was about 30 cP initially. The v iscosity of the completely molten ETCs remained sufficiently constant at 29 5 degrees C to allow time for infusion into large composite preforms. and n early all of the ETC molten sample remains a liquid for tens of seconds whe n quenched to the most desirable polymerization/solidification temperature. From the polymerization and crystallization results, it was found that the optimum polymerization temperature is approximately 230 degrees C. PET pol ymerized at this temperature had enough crystallinity for a good composite matrix; however, the molecular weights of such PETs were too low to form su fficiently strong tough matrices for composites; this is probably due to sm all amounts of impurities which produce low molecular weight PET and inadeq uate thermal stability of the cyclic stannoxane 1 initiator at this tempera ture.