Terpolymerization of p-acetylpyridine oxime, p-methylacetophenone and formaldehyde, and its thermal studies

Abstract

A terpolymer resin involving p-acetylpyridine oxime and p-methylacetophenone with formaldehyde (APOMAF) was synthesized by condensation polymerization in the presence of an acid catalyst. The structure of terpolymer was elucidated by FT-IR, 1H NMR, pyrolysis gas chromatography mass spectrometer (Py–GC–MS), nitrogen adsorption/desorption analysis, Ubbelohde viscometer and non-aqueous conductometric titration, TG–DTG and DSC. Molar fractions of monomer, condensing and comonomer unit (m1, m2, and m3) in APOMAF using 1H NMR analysis data were calculated as 1.67; 0.27 and 0.66 mol%, respectively. The apparent activation energy of terpolymer by using various degradation models including the Flynn–Wall–Ozawa (FWO), Kissinger–Akahira–Sunose (KAS), and Friedman methods were 140.3; 144.9 and 129.9 kJ mol−1, respectively. The results from isoconversional degradation kinetics and Pyrolysis (GC–MS) indicates that the degradation mechanism of terpolymer are likely limited by at least two-reaction step, the first being associated with the loss of the pendent methyl, acetyl, and oxime groups (side group elimination) while the second mass loss being due to the degradation of the terpolymer backbone (random scission) which clearly indicates that grafting pendant groups to the terpolymer backbone yields polymers with lower thermal stability. From the calculation, the solid state thermal degradation mechanism is proposed to be D3 (three-dimensional diffusion) at initial stage and F1 (Random nucleation with one nucleus on the individual particles) at final stage.