Study On The Synthesis Of Bio-Based Flame Retardant And Its Modification Of Polyurethane

In recent years,with the development of society,people put forward higher requirements for the green,safe and efficient flame retardant.Biomass materials have attracted wide attention due to their green,renewable and degradable properties.The preparation of bio-based flame retardant using biomass materials as raw materials is in line with the requirements of green strategy and sustainable development.A bio-based intumescent flame retardant PAMAD was prepared with phytic acid（PA）,melamine（MA）and dihydroxymethylpropionic acid（DMPA）as raw materials.In order to improve the compatibility of PAMAD and polymer matrix.Three series of flame retardant microcapsules（PFRM,POPM,POFM）were prepared by in-situ polymerization method using hard segment flame retardant modified polyurethane,soft segment flame retardant modified polyurethane,soft and hard modified polyurethane as wall material and PAMAD as core material.The results showed that PAMAD and three series of flame retardant microcapsules were successfully prepared.The particle size distribution of the microcapsules ranged from 0.06 to 0.20μm,and gradually increased with the decrease of core wall ratio.This corresponded to the conclusion of the encapsulation rate test of the flame retardant microcapsules.In addition,these samples were studied by thermogravimetric method of thermal stability.When the temperature was 690℃,the carbon residue rates of flame retardant microcapsule samples were 34.06%,35.22%and34.13%,respectively,which were higher than those of PAMAD.The prepared PAMAD was used as the essential flame retardant modified waterborne polyurethane（WPU）with hard section flame retardant chain extender by stepwise polymerization method,and a series of halogen-free expansion type flame retardant waterborne polyurethane PWPU with PA as the center point and outward diverging chain extension reaction were prepared.The test results showed that sample PWPU-5 with 11.00wt%PAMAD content achieved V-0 level in vertical combustion test（UL-94）with an increase in carbon residue to 11.97%.The peak heat release rate（PHRR）and total heat release rate（THR）of PWPU-5 were reduced by 45.00%and 33.80%,respectively,compared to the unflame-retardant modified sample PWPU-1.Meanwhile,the release rates of CO and CO₂ decreased by 55.80%and 33.33%,respectively.The flame retardancy of polyurethane elastomer（TPU）was improved by PAMAD.In order to enhance the compatibility between PAMAD and TPU,PAMAD was coated with soft segment flame retardant modified polyurethane by in-situ polymerization method to prepare flame retardant microcapsule（POPM）.Then POPM was added into TPU by melt blending method to prepare flame retardant PTPU composites.Results showed that when the POPM content was 30.00 wt%,PTPU30 passed the UL-94 V-0 level with a residual carbon rate of 26.70%and a limiting oxygen index（LOI）of 32.70%.Using energy dispersive X-ray spectroscopy（EDS）further analysis of the residual carbon.C,O and P were the main elements of PTPU30,in which the content of P was about 4.05%.The PHRR value,THR value and total smoke generation（TSR）of PTPU30 were reduced by70.97%,51.37%and 70.70%,respectively,compared with the pure TPU.