Synthesize and Characterization of Flame Retardant Copolyesters PET/Phosphorus Compound

Abstract

The aim of this study was to achieve a fiber‐grade poly(ethylene terephthalate) (PET) with flame retardancy properties. Flame retardant copolyesters based on ethylene glycol, terephthalic acid, and 3‐(hydroxyphenyl phosphinyl) propionic acid (HPP), as a flame retardant comonomer, were synthesized in presence of antimony trioxide catalyst at laboratory and semi‐industrial scales. At first, copolyesters with the lowest amount of flame retardant comonomer were synthesized at laboratory scale in a one‐pot reactor setup. In the second stage, flame retardant PET was synthesized in semi‐industrial pilot with HPP (PET‐HPP). The obtained copolyesters demonstrated almost identical intrinsic viscosities and other characteristics such as PET. Fourier transform infrared spectroscopy (FTIR), 1H‐NMR spectroscopy, and RMS test were performed. Flame retardancies were evaluated by a limiting oxygen index (LOI) test. The results indicated that the presence of FR significantly improved the flame retardancy and thermal stability of PET‐HPP. LOI values increased from 28% (PET) to 33 (PET‐HPP) (at laboratory scale) and 44% (at semi‐industrial scale). Differential scanning calorimetry analysis showed that the HPP polyester chain had a higher flexibility compared to PET, due to lower glass transition temperature. The effect of adding FR with regard to the thermal stability of PET‐HPP was investigated via thermogravimetric analysis. The physical properties of both the polymers are similar and suitable for textile application. J. VINYL ADDIT. TECHNOL., 25:262–270, 2019. © 2018 Society of Plastics Engineers