Synthesis of flame retardant waterborne polyurethane and investigation its use in polyester fabric coating

Nowadays, the search for high-performance, easy-to-apply, environment-friendly polymeric materials is increasing. Water-based polyurethanes are at the top of the specified materials. Due to their combustible structure, for handling flame retardant waterbased polyurethanes, it is possible to incorporate the flame retardant (FR) components into the main chain by covalent bonds or to provide a physical mixture. In order to achieve the desired FR performance in the mixture physically, the use of high amounts of FR and dispersion problems are encountered. In the scope of the study, novel waterbased flame retardant polyurethanes containing FR polyol and polyester polyol at the main chain were synthesized by combined prepolymer with acetone process as additive-free, 1, 5, 10 and 100% FR polyol content. These new polyurethanes are coated on both sides of the fabric using air blade method with 100 g/m2 dry add on content to 100% polyester fabric. Then, FT-IR, mechanical properties, flame retardant tests, thermal behavior, touch properties, light fastness, surface analysis and wear properties were tested and compared. BS EN ISO 15025, IMO (FTP code part 7), NF P 92 503 and 504 tests as demanding flame retardant tests by end-user firms for the curtain fabrics were applied to the coated fabrics. FR polyol-free polyurethane coating samples failed all tests, while the others with FR polyol passed BS EN ISO 15025 and IMO tests. On the other hand, the samples containing 100% FR polyol passed the NF P 92 504 test, but rest of them could not pass the NF P 92 503 and 504 tests. When the thermal behavior of the synthesized polyurethanes was examined, it was seen that the decomposition of the polyuretane containing 10% FR polyol began significantly lower temperature compared with those containing lower amounts of FR polyol. The amount of the solid residue increased as the percentage of FR polyol increased, in accord with the success in the flame retardant tests by forming the char layer. The surface of coated fabrics were examined with SEM and it was seen that a homogeneous coating with a thickness of 70 μm was achieved, and the coating was not damaged even after 5000 cycle in the abrasion test. The tensile strength was measured in the film form to avoid the fabric strength and elongation up to 500%, the failure in the strength of all the samples except for that with 100% FR polyol was not observed. As the amount of FR polyol increased, the strain decreased while similar elongation was observed. However, breaking at 49.06% elongation was observed for the film containing 100% FR polyol. In the coated fabrics, the touching values were measured numerically with a Handle O-Meter, and the stiffness value in the weft and warp direction increased as the FR polyol ratio increased. and these results are consistent with those obtained by strength tests, indicating that the presence of polyester polyol adds flexibility to the structure. Finally, coated fabrics were tested for light fastness and FR polyol free and the sample with 1% FR polyol are rated as 7 (the best being 8 according to the blue wool scale), while the others are rated 6. These values are quite sufficient. Considering the all test results, the sample containing 1% FR polyol was recommended as the most suitable one. In the scope of this thesis, a green, flame retardant water based polyurethane coated polyester fabric was prepared. Flame retardancy was achieved at a very low percentage of FR polyol due to bonding to the back bone of the polymer as evaluated with commercial tests. Keywords: Waterborne, polyurethane, flame retardant, coating.