Reaction process in polycarbonate/polyamide bilayer film and blend

Abstract

Bisphenol-A polycarbonate (PC) and amorphous polyamide (aPA) were used as reactive system to study the interfacial interchange reaction between condensation polymers. Aminolysis is the main process during thermal annealing at 160–180 °C. The simultaneously scission of PC chains and formation of PC-aPA copolymer chains during the reaction process, can act as interfacial compatibilization agents between incompatible homopolymers. Reaction kinetics measured by in-situ Fourier transform infrared spectrum (FTIR) at interfaces of well-separated bilayer films and phase separation blends were compared. The reaction follows a first-order diffusion controlled mechanism and three time regimes were observed. First, the functionalized chains located in the vicinity of the interface participate into the reaction and the annealing time dependence of the integral area of difference IR spectra follows a power law relationship as [Area] ∼ t1/4. Second, a depletion layer of reactants in the interfacial region is formed with the progression of reaction, and center-of-mass diffusion of reactants is required for further reaction which results in a transition of the power law relationship into [Area] ∼ t1/2. Finally, the potential barrier arising from the previously formed copolymers at the interface suppressed the reaction. When the conversion reaches a critical value, thermal fluctuation can induce interface destabilization. An acceleration of reaction rate observed by FTIR for sample annealed at 180 °C is synchronous with the interfacial roughness development analyzed by atomic force microscopy.