Preparation Of Phosphorus Doped Silica Sol And Flame Retardant Finishing Of Silk And Wool Fabric

Phosphorus doped silica sols were prepared using phosphorus based flame retardants as additive via sol-gel method, and applied on silk and wool fabric.Pure silica sol was prepared using tetraethoxysilane(TEOS) as precursor, ethanol(Et OH) as co-solvent, hydrochloric acid(HCl) as catalyst, and then applied onto silk and wool fabric respectively. Taking the LOI values of the treated fabrics as evaluation index, the effects of the preparing condition such as n[TEOS]:n[H2O], n[TEOS]:n[Et OH], reaction p H value, reaction temperature and time and finishing process such as pick-up value, baking temperature and time on the flame retardancy of finished silk and wool fabrics were discussed. On the basis of optimized silica sol preparation conditions, phosphoric acid, ammonium dihydrogen phosphate and dimethyl phosphate were doped into the silica sols respectively in order to improve the flame retardancy of the sol system and also the effect of different content of phosphorus was discussed when applied on the fabric. As the result, the preparing condition was optimized as follows: n[TEOS]:n[H2O]:n[Et OH]=1:1:3 for pure silica sol while n[TEOS]:n[H2O]:n[Et OH]=1:20:3 for phosphrous doped silica sols, p H=2, reacted 3 hours at 70℃. The optimal finishing conditions were as follows: two dipping-two padding, pre-dried, cured at 160℃ for 6 minutes. 8% ammonium dihydrogen phosphate doped silica sols was proved to be the effective Si/P sol system. Si/P treated silk and wool fabric with 31.7% and 29.7% of LOI value could be obtained, respectively.The particle size and infrared spectroscopy of the sols were characterized, indicating the homogeneous, stable and nano-size sol systems were prepared. The result of thermo analysis indicated that the thermal stability of the sol was improved when doped with phosphorus. The morphology, structure and element composition of the surface of the treated fabric were analyzed using scanning electron microscopy, X-ray photoelectron spectroscopy and X-ray diffraction. The analysis results demonstrated that the sols were modified to the fabric successfully. The flammability and thermal properties of the treated fabric were tested by limited oxygen index, vertical firing tests, micro combustion calorimeter and thermogravimetric analysis. The results showed the flame retardance of the silk and wool fabric treated by phosphorus doped silica sol was greatly improved.