Effects Of Electron Beam Radiation-induced Grafting On The Flame Retardant And Anti-dripping Performance Of Nylon 6,6 Fabric

Nylon 6,6 has been widely used in the fields of clothing, home textile, industrial products and so on with its excellent strength, elastic recovery, abrasion resistance and dyeing property. However, its flammability especially the serious melting dripping in the burning process, easily make other materials burn and brings about huge economic losses and personal injury, which restrains the further applications of nylon6,6 fabrics to some degree.In our study, the irradiation and the following grafting modification of nylon 6,6fabrics were conducted on a RHODOTRONTT 200 type electron accelerator made by IBA company, Belgium. The main researches are as follows: under the different irradiation doses in the range of 0 to 700 kGy on nylon 6,6 fabric, the effects of irradiation doses on the intrinsic viscosity, orientation, crystallization and melting behaviors, surface morphology and mechanical properties of these irradiated fabric samples were investigated. Taking acrylic acid(AA) as a grafting monomer, the optimal preparation conditions were achieved by orthogonal experiments and the anti-dripping performances of grafted samples were evaluated. 2-hydroxyethyl methacrylate(HEMA) and N-Methylol acrylamide(N-MA) were introduced to the grafting system and the effects of the multiplex monomer system on the anti-dripping performances and wearing properties of nylon 6,6 fabric were studied. In order to acquire anti-dripping and flame retardant performance simultaneously, an unsaturated phosphorus-containing flame retardant monomer, 2-hyroxyehyl methacrylate phosphate(HEMAP), was selected together with AA for the grafting reaction. The effect of monomer ratios on the grafting reaction was studied as well. And flame retardant mechanism was proposed dependent on the discussing of the anti-dripping and flame retardant performances of the prepared nylon 6,6 fabric samples.The results indicate that:(1) with the increase of the irradiation dose in the above range, the original crystal structure of fibers is not altered. The crystallinity of fibers raises with the increasing irradiation doses, which was due to the chain segmental rearrangement in the amorphous area during the irradiation process. Meanwhile, the orientation degree of molecular chains is also improved. Both the crystallization and melting temperatures of fibers shift to a lower degree. These results suggest that the irradiation mainly causes the oxidative degradation of molecular chains and the significant decrease of thermal stability of irradiated fibers. When the irradiation dose reaches 700 kGy, the micro-cracks appear on the surface of fibers leading to an increase of stress concentration and destroy the mechanical properties of these irradiated fibers.(2) the optimal grafting conditions obtained are as follows: 20 wt% monomer;180 kGy irradiation dose and 0.08 wt% inhibitor. With the increase of grafting ratios,the onset temperatures of grafted samples decrease gradually, while the char-forming performance enhances significantly. Besides, the damaged length and droplet velocity of the grafted samples become shorter and lower. It is concluded that the improvement of anti-dripping performance of these grafted samples can be attributed to the earlier decomposition of grafting polymers and the forming of a cross-linked char layer on the fiber surface. And the char layer provides a support for the melting fiber.(3) A high grafting efficiency is observed in both HEMA-g-PA66 and N-MA-g-PA66. Compared with HEMA/AA-g-PA66, N-MA/AA-g-PA66 has lower initial decomposition temperature, smaller maximum mass loss rate and better char-forming performance. The damage length, droplet velocity and time for the appearance of first drip observed in N-MA/AA-g-PA66 are much shorter, lower and longer than HEMA/AA-g-PA66 despite there is still a higher droplet velocity in N-MA/AA-g-PA66 compared with AA-g-PA66.(4) The initial decomposition temperatures of HEMAP&AA-g-PA66 are much lower than pure nylon 6,6 fabric. The LOI value and char residue at 800 ℃ reach27.0 % and 16.0 % when the concentrations of HEMAP and AA are 15.0 wt% and 5.0wt%, respectively. The grafted samples have longer igniting time, shorter after flametime and damaged length. With the increasing content of AA, the anti-dripping performance of grafted samples is improved gradually. It is concluded that HEMAP plays a major role in the condensed phase, promoting the formation of large amounts of char. The improvement of flame retardancy may be attributed to the compact char layer which not only prevents the release of flammable gases and oxygen invasion,but also cuts off the exchange of heat and substances.