Preparation And Charactetrization Of Flame Retardant Polyurethane Elastomer

Polyurethane elastomer（PUE）is a special viscoelastic material which is used in many fields because of its advantages of light weight,high strength,high elasticity,wear resistance,good damping and shock absorption.However,PUE is mainly composed of carbon chains,so the matrix is highly flammable,and generates a large number of drops and toxic gases during the burning process.In addition,PUE usually has a narrow effective damping temperature range,so when the working temperature exceeds the effective damping temperature range,the damping failure will occur.These problems restrict the development of practical engineering applications.Therefore,it is an urgent need to prepare high flame retardant and damping PUE to meet the increasing engineering needs.In order to overcome the disadvantages of poor compatibility,severe damage to mechanical property and migration faced by additive flame retardant/damping modification.Due to the special aggregation state structure,micro-phase separation ability and performance adjustability of PUE.This thesis will do the modification of the material by molecular structure design,select polyols with suspension side chains and DOPO side groups as chain extenders,respectively.Finally obtain polyurethane elastomers with excellent overall performance.The specific research content and results were as follows:1.To investigate the effect of suspension side chain length in the system on the performance of flame retardant polyurethane elastomer.Polyols with different suspension chain length were selected as chain extenders to react with diphenylmethane diisocyanate（MDI-50）,and the same amount of dimethylphosphonate（DMMP）was added to each system.The five flame retardant polyurethane elastomers with different suspension chain length were prepared by prepolymer method.The relevant tests showed that with the increase of the length of the suspension chain in the system,the slip and internal friction between molecular chains were increased,the peak of the loss factor(tanδ_max)was increased from 0.33 to 0.94,the effective damping temperature rang was widened from 17.9～44.0℃to-23.0～40.0℃,the glass temperature（Tg）was decreased from 31.1℃to-1.5℃.Meanwhile,with the compatibility of polyurethane soft and hard segments increased,the degree of microphase separation was decreased,and the root mean square roughness（Sq）and average roughness（Sa）of the material surface were decreased by 78.4%and 84.0%.With the increase of the compatibility of DMMP and PUE,the thermal decomposition rate and combustion heat release rate of the system were improved.In addition,due to the presence of the suspension chain,the compliance of the molecular segment was increased,the elongation at break of the material was increased from 342%to 694%.2.To investigate the effect of reactive DOPO derivative on the performanceofflameretardantpolyurethaneelastomer.10-（2,5-dihydroxyphenyl）-10-hydro-9-oxa-10-phosphophenanthrene-10-oxide（DOPO-HQ）was selected as a chain extender to partially replace1,4-butanediol（BDO）for PUE modification.The reactive flame retardant polyurethane elastomer was prepared by prepolymer method.Compared to PUE without flame retardant modification,when the content of DOPO-HQ was 20 wt%,the limiting oxygen index（LOI）of the modified polyurethane was improved from 21.0 to 28.9.The relevant peak heat release rate（p HRR）was reduced from 2301 k W/m²to 562 k W/m²,total heat release（THR）was reduced from 118.5 MJ/m²to 66.9 MJ/m²and total smoke production（TSP）was reduced from 66.3 m²to 30.4 m²,were decreased by 75.6%,43.6%and54.1%.In addition,the degree of micro-phase separation of polyurethane soft and hard segments and the roughness of the material surface were increased.The corresponding heat loss of the system was increased.The tanδ_maxwas increased from 0.39 to 0.52,the effective damping temperature rang was widened from-4.1～25.2℃to 14.2～60.8℃.The tensile strength of the material was increased from 11.7 MPa to 18.2 MPa.3.To investigate the effect of the suspension side chain and DOPO side group on the performance of flame retardant polyurethane elastomer.Firstly,a new flame-retardant polyol with symmetrical structure of suspension chain and P/N flame-retardant group was successfully synthesized by the two-step reaction of 2-Amino-1-butanol,1,4-Phthalaldehyde and DOPO.The reactive flame-retardant polyurethane elastomer was prepared by chain expansion reaction with MDI-50.Compared to PUE without flame retardant modification,when the content of PABD was 15 wt%,the LOI value was improved from 21.0 to 29.1,and through the UL-94 V-0 flame retardant rating.The p HRR was reduced from 2301 k W/m²to 399 k W/m²,THR was reduced from 118.5 MJ/m²to 59.8 MJ/m²and TSP was reduced from 66.3 m²to 19.4m²,were decreased by 82.6%,49.5%and 70.7%.In addition,under the effect of alternating stress,the heat loss of polyurethane in the process of force was increased.The tanδ_maxwas increased from 0.39 to 0.74,the effective damping temperature rang was widened from-4.1～25.2℃to 1.4～55.5℃.Meanwhile,the degree of crosslinking of the system was increased,the tensile strength of the material was increased from 11.7 MPa to 24.4 MPa.