An intumescent coating system modified with waste poly(ethylene terephthalate) as a substitute for dipentaerythritol

Abstract A solvent-borne poly(vinyl acetate)-based intumescent paint containing ammonium polyphosphate, melamine, zinc borate (ZB) and dipentaerythritol (DPER) was modified with powdered poly(ethylene terephthalate) (PET) from post-customer bottles; the polymeric microfiller substituted 6–50 wt.% of DPER. Thermal insulation features of dry coatings were investigated by means of a gas flame-heated furnace (according to a cellulosic fire curve). Thermogravimetrical (TG, DTG) and thermal (DSC) features, a chemical structure (FTIR) and mechanical strength of the coatings and obtained chars were analyzed as well. It was revealed that PET positively affected the thermal insulation time (up to 450 °C of a steel substrate) and intumescence effectiveness of coatings, but reduced compressive strength of the created chars. The highest value of the thermal insulation time (+34%) was noted for a sample containing 6/94 m/m PET/DPER while the largest expansion (+54%) was observed for a coating with a 25/75 m/m PET/DPER mixture. Additionally, an influence of ZB on crosslinking, transesterification and/or thermal degradation processes of the applied binder, PET and DPER was presented and discussed.