ToF-SIMS investigation of the thermally induced processes at the surface of polyester based polymer blends

Surface evolution caused by thermal processing at 270 degreesC of blends of bisphenol-A polycarbonate (PC) with polyethyleneterephthalate (PET) or with polybuthyleneterephthalate (PBT) has been investigated by ToF-SIMS. Such systems are known, upon melt mixing, to undergo transesterification reactions leading to the formation of copolymers. In the case of PET-PC, the transesterification is accompanied by reactions involving the loss of small molecules from the resulting copolymer, whereas the copolymer resulting from the trans-esterification of PBT-PC is stable at the temperature under consideration. We report on Static SIMS measurements performed on blend samples melt mixed for different times, that show a complex evolution of surface composition, explained also in terms of surface-specific processes, such as segregation of lower surface free energy components. The results from the melt mixed system are compared with those obtained from parallel temperature-programmed ToF-SIMS experiment, performed on spin-cast thin films