A novel phosphorus-containing copolyester with low melting temperature and high flame retardancy

BACKGROUND: The increasing uses of non-woven fabrics need the development of a kind of novel flame-retardant polyester with low melting temperature. Neopentyl glycol (NPG) and 3-(hydroxyphenylphosphinyl)propionic acid (HPPPA) were used as the third and fourth comonomer to synthesize phosphorus-containing poly[ (ethyl en e terephthalate)-co-(neopentyl terephthalate)] (PENT) with both flame retardancy and low melting temperature. RESULTS: The chemical structure of PENT was confirmed using Fourier transform infrared, H-1 NMR, C-13 NMR and P-31 NMR spectroscopy. PENT displays a monomodal gel permeation chromatography curve. When the content of NPG was kept at 10 wt% and the content of HPPPA increased to 5 wt%, the melting temperature (T-m) of the resulting PENT5/10 decreases to 171.2 degrees C, a 34.6 degrees C decrease compared to that of PENTO/10 (containing no HPPPA). The flammability of the PENTs was characterized with the limiting oxygen index (LOI) test, the UL-94 vertical test and the cone calorimeter test. The incorporation of HPPPA can significantly improve the flame retardancy of the PENTs, the LOI values of the PENTs increasing from 24.4 to 37.6, as the loading of HPPPA increases from 0 to 5 wt%. CONCLUSION: The PENTs possess both low melting temperatures and excellent flame retardancy. HPPPA can be used as fourth comonomer to improve the flame retardancy of the PENTs, while decreasing the T-m value of the copolyester. (C) 2009 Society of Chemical Industry