Effects of novel functionalized magnesium phosphate monomers on the flame retardancy and mechanical properties of polyethylene terephthalate copolymers

In this study, inorganic magnesium hydroxide (MH) was modified by three phosphoric acids respectively to obtain three different novel functionalized monomers. The chemical structure and morphology of (Pn-MH) were analyzed by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Further, functional monomers were introduced into the PET main chain structure. A new type of high-performance co-polyesters was successfully prepared. The specific structure of P1-MH-PET was characterized by 1H NMR spectroscopy. Thermal stability of Pn-MH-PETs was analyzed by thermogravimetric analysis (TG) and differential scanning calorimetry (DSC). The flame retardant properties were evaluated by limiting oxygen index (LOI), vertical combustion test (UL-94) and cone calorimeter. The results show that the thermal stability and flame retardant properties of 5%Pn-MH-PETs are greatly improved. Among them, the best performance is 5%P1-MH-PET, LOI is 32.5%, UL-94 test reached V-0 grade. Compared with neat PET, the peak heat release rate (PHRR), peak smoke release rate (PSPR), carbon dioxide release rate (CO2PR) and carbon monoxide release rate (COPR) decreased by 57.0%, 38.1%, 54.6% and 57.3%, respectively. Fortunately, the mechanical properties of 5%P3-MH-PET were also improved.