Improving charring behaviour of Nylon 6.6 via ionic introduction of inorganic esters

Polymeric materials incorporated with phosphorus or boron containing compounds exhibit enhanced char formation when exposed to open fire. In this work, different ester mixtures of phosphoric acid and boric acid were prepared and the correlation between their charring level and degree of esterification (ED) was studied. The ester mixture with the highest remaining char ratio was introduced to Nylon in formic acid solution at 110 °C for 30 minutes. A thin film of treated Nylon 6.6 slurry was prepared and cured at 130 oC for 30 min. Thermal analysis was carried out using a thermogravimetric analyser (TGA), and the formation of new bonds were verified by Fourier transform infrared spectroscopy (FTIR) after washing. A general ionic mechanism for grafting the ester mixture to nylon 6.6 was proposed based on FTIR results.