Synthesis,Characterization And Application Of Post-chain Extended Flame-retardant Waterborne Polyurethane Based On Bis(4-aminophenyl) Spirocyclic Pentaerythritol Phosphonate

The development of halogen-free flame retardant waterborne polyurethane is an important research direction of modified waterborne polyurethane.Flame retardant waterborne polyurethane has larger application range and better application prospect.Among the different flame retardant modification methods,post-chain extension technology can not only greatly improves the flame retardancy of waterborne polyurethane,but also possess many advantages that include simple operation,low energy and less solvent consumption,and good mechanical properties of the products.Frist,a phosphorus-containing diamine flame retardant bis(4-aminophenyl)spirocyclic pentaerythritol phosphonate(BPPA)was synthesized and used as post-chain extender.Then,a series of post-chain extension flame retardant waterborne polyurethanes(B-WPUs),postchain extension flame retardant waterborne polyurethanes with soft segment modified by ExolitOP550(B-SWPUs)and a series of post-chain extension flame retardant waterborne polyurethanes with hard segment modified by Fyrol-6 were prepared.Fourier transform infrared spectroscopy(FTIR)and energy dispersive spectrometer(EDS)were utilized to characterize the structures of the waterborne polyurethanes.The emulsion properties inculding particle size and stability,and the film properties inculding mechanical,flame retardant and thermal properties were investigated.The thermal decomposition of post-chain extension flame retardant waterborne polyurethane was investigated by thermogravimetric analysis(TGA),TGA-FTIR,and the FTIR of the solid phase degraded products.The effects of BPPA post-chain extension on the structures and properties the flame retardant waterborne polyurethanes emulsion and filmswere discussed.B-WPUs,B-SWPUs and B-HWPUs were used as fabric coating agents,and the amount of coating agents,the sensation,fastness,fracture strength,flame retardant properties,and hydrostatic resistance of the coated textiles were measure.The results of the experiments show that,the three types of post-chain extension flame retardant waterborne polyurethanes were successfully prepared.The content of phosphorus were close to the theoretic value.With the increasing of the BPPA,the particle size increased,but the stability of emulsion reduced.The films exhibited increased tensile strength as well as decreased elongation at break with the increasing of BPPA content.The tensile strength of these polyurethanes was in the order of B-HWPUs >B-WPUs > B-SWPUs at the same post-chain extension ratio.Oxygen index and UL-94 tests showed that flame retardant properties improved with the increase in BPPA content.When the post-chain extension ratio was 80%,the LOI and UL-94 of B-WPUs reached 29.0% and V-1,respectively;those of BSWPUs reached 30.9% and V-0,respectively;and those of B-HWPUs reached 30.2% and V-0,respectively.TGA measurements showed that the degradation temperature of B-SWPUs and BHWPUs were lower than those of B-WPUs.The post-chain extension of BPPA promoted the thermal degradation process and significantly increased the residual char yields at 600?.The thermal degradation processes of B-WPU,B-SWPUs and B-HWPUs were studied by TGA,TGA-FTIR and FTIR of solid phase degraded products.The results showed that the thermal degradation process includeed two steps.The first step was the degradation of hard segments.During the first step,the organophosphorus(BPPA,ExolitOP550 and Fyrol-6)was degraded into polyphosphoric acid or polyphenyl phosphate.Then the hard segments decomposed into carbon dioxide,isocynates and polyols.The second step was the degradation of soft segments,polyols decomposed into ethers,aldehydes,ketones,olefins and char.The results of their application on fabric coating showed that with the increasing contents of BPPA,the handles were poorer,the flame retardant properties and breaking strength improved,but the hydrostatic pressure and fastness decreased.When the post-chain extension ratio was 80%,fabrics treated by B-SWPUs and B-HWPUs could reach B1 level according to GB/T5455-1997 vertical combustion standard.The descending order of the hydrostatic pressure was B-WPUs > B-HWPUs > B-SWPUs,while that of the flame retardant property was B-SWPUs> B-HWPUs>B-WPUs.