Preparation And Properties Of Rigid Polyurethane Foam With Boron And Nitrogen Structure

The Rigid Polyurethane Foam(RPUF)material has the characteristics of light weight,low thermal conductivity and good dimensional stability.It has been widely used in many fields,especially in the field of external wall heat-insulating board.RPUF has the advantages of high strength,and excellent insulation performance compared with Expanded Polystyrene(EPS)and Phenolic Foam(PF).However,the application of RPUF is limited by the inflammable.The halogen-containing flame retardants produce a large amount of smoke and even corrosive and poisonous gases during combustion.Phosphor-containing flame retardants have the problems of volatile,poor compatibility,dropping,and pollution of soil and water.The nitrogen-containing flame retardants alone to be weak and ineffective,and it is often used in retardants mixed system.Boron flame retardants have the advantages of low toxicity,low smoke and burn without dropping.To the best of our knowledge,investigation of boron and nitrogen-containing flame retardants which contains boroxin and nitrogen compounds as intramolecular synergistic agents in improving the fire performance of RPUF has not been reported so far.The flame retardant of boron and nitrogen in the molecule will be applied to the condensed phase and gas phase of the RPUF combustion,and the flame retardant mechanisms are synergistic on the surface of RPUF.The reactive boron flame retardant and B-N flame retardant were prepared by molecular structure design,and used as a reactive flame retardant to the molecular structure of the rigid polyurethane foam.The main contents were given as follows:1.A reactive boron flame retardant Trihydroxypropyl borate(TBOH)was synthesized with boric acid and 1,3-propanediol as raw materials,and characterized by Fourier Transform Infrared(FT-IR)spectroscopy,Nuclear magnetic resonance(1H-NMR),Inductively Coupled Plasma emission(ICP)spectroscopy,thermal stability have been analyzed by Thermogravimetic analysis(TGA).FT-IR showed that the stretching vibration band of B-O was 1350 cm-1,3380 cm-1 was the vibration band of-OH.The area of the proton peak with different chemical shift was 6.07:2.61:12.01,it was basically the same as the theoretical ratio.ICP indicated the boron contents was 4.46%,the TBOH initially decomposes at around 195?,the residue at 600? was 5.5%.The method of manual one-step foaming was prepared to manufacture the flame-retardant rigid polyurethane foam.Physical characteristics of material such as density,water absorption rate,dimensional stability are measured and analysed.The results suggest that the density of the material ranged from 48.5-50.5 kg/m3,the water absorption rate was below 1.1%,the change rate of dimension stability in long,wide and thick direction is below 0.5%.The thermal stability,flame retardant property and the morphology of material were characterized by TGA,limit oxygen index(LOI),and scanning electron microscope(SEM).The results showed that the volume change rate of TBOH-RPUF is under 1%when TBOH is more than 10%,the carbon residue rate over 23%at 600?,the LOI increased more than 22%.2.A reactive boron and nitrogen containing flame retardant(4,4',4"-(boroxin-2,4,6)-tri(3-amino-2-hydroxymethyl)benzamide polyetherpolyols)was prepared with 4-carboxyphenylboronic acid and 1,3-diamino-2-hydroxypropane as raw materials,and characterized by FT-IR,'H-NMR and TGA.FT-IR showed that the frame vibration band of B3O3 was 691 cm-1,759 cm-1.1361 cm-1 was the stretching vibration band of B-O.The backbone vibration band of benzene ring was 1450-1600 cm-1.The initial decomposition temperature of NBOH was 215?,the amount of residual carbon was 32.5%at 600 0C.The method of manual one-step foaming was prepared to manufacture the flame-retardant rigid polyurethane foam(NBOH-RPUF).The thermal stability,flame retardant property,chemical composition and morphology of the flame-retardant foams and the carbon residue were characterized by TGA,LOI,FT-IR,SEM,EDX and Laser Confocal Raman Microspectroscopy respectively.NBOH contains a lot of aromatic ring structure,and the RPUF molecular chain has strong cohesion and stability.The molecule of NBOH-RPUF contains boroxin(B3O3)and nitrogen structure,showed excellent B-N synergistic flame retardant effect.The results showed that when 30%NBOH was added,the limit oxygen index was more than 24.5%,the tempreature of 50%weight loss is above 368 ?,the residue at 800 ? is above 29.5%and demonstrating that the introduction of the boroxin group into the polymer helped to improve the smoke suppression effect.