Synthesis And Properties Of Flame-retarded Nylon Modified By Copolymerization

Nylon 66 is a widely used engineering plastic or fiber material, occupies an important position in all areas of national life and production. With the widely used in many fields, such as appliances, transportation, construction, interior decoration and so on, there is a potential fire safety hazards in the application process because of the flammability of PA66. In recent years, the green flame retardant become the development trend, especially 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide(DOPO) and its derivatives which containing phosphaphenanthrene group were obtained more and more attention due to the excellent performance.In this paper, DDP ([(6-oxido-6H-dibenz[c,e][l,2]oxaphosphorin-6-yl)methyl] butanedioic acid) was first prepared from DOPO and itaconic acid in the molten condition. Then the DDP salt was synthesized through the reaction of DDP and hexamethylenediamine. Their structures were characterized by fourier transform infrared spectroscopy (FTIR), and the melting point of DDP were measured by differential scanning calorimetry (DSC).Phosphorus-containing co-polyamides (DDPPA) were prepared from nylon66 salts and DDP salt via melt polycondensation. Through the test of intrinsic viscosity the best content of DDP salt was 30%, and the optimum reaction conditions were obtained. The structure of the copolymer was characterized by fourier transform infrared spectroscopy (FTIR). Differential scanning calorimetry (DSC) test showed the glass transition temperature(Tg) was 43.8℃. Its thermal stability was measured by thermogravimetric analysis (TGA), which exhibited good thermal stability below 280℃.Blends of polyamide 66 and DDPPA were prepared via melt extrusion. The flame resistance, thermal degradation kinetics, crystallization property, crystallization kinetics, mechanical properties and rheological behaviors of blends were investigated by oxygen index detector, thermogravimetric analysis, X-ray diffracmeter, differential scanning calorimeter, mechanical testing machine, capillary rheometry, respectively. The LOI test and TGA analysis showed that adding DDPPA can lead to advance thermal degradation, but the flame retardancy can be improved by the increase of char yield. When the loadings of DDPPA were 5%, the LOI increased from 26.0 to 28.2. Adding DDPPA can improve the bending properties, when the loadings of DDPPA were 5%, the strength were increased from 71.44MPa to 76.52Mpa, but the tensile strength and impact strength had a slight decrease. With the content of DDPPA increasing, the crystallinity decreased and the crystallization ability declined; the apparent viscosity of melting blends decreases and the processability improves.