Effect of methylmetacrylate units on the non-isothermal degradation kinetics of St-MMA copolymers

Some different kinetics models have been used for estimating the kinetics parameters of different polymers and copolymers [1-3]. In this study, the activation energies of differentcopolymers have been calculated using Flynn-Ozawa-Wall [2] method and compared with each other as well as with corresponding homopolymers. Materials and methods Styrene-Methylmethacrylate (St-MMA) random copolymer in different compositions, polystyrene (PS) and polymethylmethacrylate (PMMA) were synthesized by suspensionpolymerization. The Flynn-Ozawa-Wall method is useful for the kinetics interpretation of the TG data obtained from complex reactions: (1) ln ln( ) ln ( ) 5.3305 1.052( ) RT g E R   AE     The slope of the line will be equal to -1.052E/R during a seriesof measurements with different heating rates at a fixed degree of conversion. To study the degradation mechanisms of the samples, various expression of differential, f(α), and integral, g(α), forms of the different solid state mechanisms have beenproposed [3] and several analytical models have been used to estimate the Arrhenius parameters. One of such models is Coats-Redfern equation [4]:(2) RT E EAR Tln g( )  ln( )  2 The linear plot of ln[g(α)/T2] versus 1/T makes it possible to determine E and ln(A) from the slope and intercept of the graph, respectively.