Thermal degradation and stability of accelerated-curing phenol-formaldehyde resin

In order to study the thermal stability of accelerated-curing PF resin, the curing behavior of fresh PF resin was investigated in the presence of single accelerator of methylolurea derivatives (MMU), magnesium hydrate (Mg(OH)2), 25% aqueous solution of sodium carbonate (Na2CO3), and propylene carbonate (PC). Also their optimum combination was added in fresh PF resin. The thermal stability of cured phenol-formaldehyde (PF) resins was studied using thermogravimetric analysis TG/DTA in air with heating rates of 5, 10, 15, and 20 °C min-1. Thermal degradation kinetics were investigated using the Kissinger and Flynn-Wall-Ozawa methods. The results show that these accelerators can promote fresh PF resin fast curing, and the degradation of accelerated-curing cured PF resin can be divided into three stages. Single accelerator MMU, Mg(OH)2, and Na2CO3 can promote fresh PF curing at low temperatures in the first stage, while the structure of PF resin which was added with MMU and PC was more rigid, according to thermal degradation kinetics. A novel fast curing agent which is compound with MMU+Na2CO3 for PF resin is proposed; not only can it maintain the advantage of fast curing of the single accelerator Na2CO3, but it also improves the thermal stability of PF resin.