Mechanical Properties and Atomic Force Microscopic Cross Sectional Analysis of Injection Molded Poly(ethylene terephthalate-co-4,4'-bibenzoate)

A series of poly(ethylene terephthalate-co-4,4'-bibenzoate), PETBB, copolymers were prepared using isomeric 2,4'-, 3,4'-, and 4,4'-bibenzoate monomers. Only the 4,4'-bibenzoate copolymers produced the desired, high temperature, semicrystalline materials. As a result, a PETBB copolymer containing 55 mole% 4,4'-bibenzoate was scaled up and injection molded, along with poly(ethylere terephthalate), PET, and poly(butylene terephthalate), PET, homopolymers. The PETBB copolymer was demonstrated to give shorter injection molding cycle times than PET (known for its short cycle times), and exhibited better thermal properties than either homopolymer. The PETBB copolymer exhibited 40-50% higher tensile and modulus properties when compared to PBT injection molding resin. An examination of cross-sections of the PETBB molded bars by atomic force microscopy showed these bars to be morphologically homogeneous, with no discernable surface skin effects. Details of the PETBB morphology are shown in the AFM images presented.