Novel Polyurethane Electrical Insulator Coatings Based on Amide-Ester-Ether Polyols Derived from Castor Oil and Re-cycled Poly(ethylene terphthalate)

In order to utilize renewable resource raw materials as well as trying to recycle polymeric materials, three new polyols (PEEA1-3) were prepared. Bottle grade recycled poly(ethylene terphthalate) was subjected to transesterification and an amidation reaction with different molecular weights of poly(ethylene glycol) and diethanol amine. The intermediate hydroxyl-terminated compounds were chain extended via an esterification reaction with adipic acid and the products were reacted with castor oil. Polyurethane networks were prepared through the reaction of PEEA1-3 with librated isocyanate groups of a blocked isocyanate curing agent made from trimethylol propane, toluene diisocyanate and N-methyl aniline. All of the starting materials and final cured films were characterized by conventional methods. The curing condition was optimized via gel content measurements. The crosslink density of the samples was determined via an equilibrium swelling method, using the Flory-Rehner equations. The effects of structural parameters on the physical, electrical, mechanical, and dynamic mechanical properties of the polyurethane coatings were evaluated. Investigation of the results showed that the prepared green coatings have environmental benefits as well as high performance as metal insulator coatings.