Development Of PIR-PUR Foam With Enhanced Flame Retardancy Aided By DMMP@ Porous Material Composite

Polyisocyanurate-polyurethane(PIR-PUR)foam is a building material with good insulation capacity but easy to combust.Therefore,enhancing the flame retardancy is imperative.Dimethyl methylphosphonate(DMMP),a flame retardant with high phosphorus content up to 25%,is suitable for increasing flame retardancy of other materails.According to the previous studies,when the addition of DMMP is high enough,it will cause unacceptable shrinkage,the addition of DMMP is limited and the flame retardancy of DMMP cannot be fully initiated.Therefore,this study is aiming for DMMP @ porous material composite which is prepared by the adsorption of DMMP on porous materials,and used to enhance the flame retardancy of PIR-PUR foam.This study investgated the effect of addition of DMMP on the properties of PIR-PUR foam and determine whether the flame retardancy of PIR-PUR could meet the requirements of B1 grade flame retardant material by adding DMMP.The results show that the LOI value of PIR-PUR foam increases with the dosage of DMMP,and the LOI value of PIR-PUR reached up to 31.5% when the addition of DMMP is 15%,which meets the requirement of grade B1 flameretardant material.In combustion test,both the PHRR and THR of PIR-PUR foam sample with 15 % DMMP content are decreased by 66%,the TSR value is decreased by 82% and the residual carbon content is increased by 14%,which indicated that the flame retardancy and smoke suppression properties of PIR-PUR foam were improved by the addition of DMMP.The larger the content of DMMP was added,the more obviously "petal" shrinkage deformation of PIR-PUR foam sample was found.The maximum linear shrinkage rate of PIR-PUR foam sample was 11.0% when the content of DMMP was 15%,and the phenomenon of recovery is shown.In order to solve the shrinkage problem of PIR-PUR specimen caused by DMMP,the DMMP @ porous material was used to modify PIR-PUR.Diatomite was used as porous material to studied the adsorption efficiency of diatomite to DMMP by four adsorption methods: direct heating adsorption,water bath adsorption,vacuum oven depression adsorption and vacuum immersion adsorption.The results showed that vacuum immersion adsorption had the best adsorption efficiency,up to 90.23%.The adsorption efficiency of DMMP on five adsorption materials,diatomite,molecular sieve,organically modified montmorillonite(OMMT),expanded graphite,and silica aerogel were studied by vacuum immersion adsorption method.the results showed that the aerogel has the highest adsorption efficiency,up to 805.82%.The DMMP @ aerogel composite flame retardant was prepared by vacuum immersion adsorption method,and then the composite flame retardant was added to the PIR-PUR foam to study the effect of DMMP @ aerogel additon on the properties of PIR-PUR.The results showed that with the increase of DMMP @ aerogel addition,the LOI value of PIR-PUR samples increased gradually,and the LOI value of the samples with 15% DMMP was 30%,which meets the requirement of grade B1 flameretardant material.In the combustion test,the PHRR,THR,SPR and TSR of the sample were between the pure PIR-PUR sample and the D15 sample.This indicates that the DMMP @ aerogel composite can be used to modify the PIR-PUR material.It can improve the flame retardancy of rigid polyurethane foam and has a certain smoke suppression effect,but it is not as good as that of the sample with 15% DMMP alone.Dimensional stability of PIR-PUR foam specimen with DMMP @ aerogel composite is better than pure PIR-PUR,the size change rate of PIR-PUR foam is less than 5% when the content of DMMP is up to 15%.The shrinkage regularity and mechanism of PIR-PUR foam were studied by several methods.The results showed that after peeling and curing,the size change rate of D15 sample is less than 2%,and the shrinkage recovery of PIR-PUR/DMMP can be accelerated with temperature rise.The investigating results by SEM showed that the increase of DMMP content did not change the cell diameter of PIR-PUR foam,and the synthesis of DMMP and EG into DMP did not cause the shrinkage of PIR-PUR foam.TMP,with similar boiling point of DMMP,also makes the PIR-PUR foam shrink,but the shrinkage ratio is smaller than that of PIR-PUR/DMMP.So the shrinkage mechanism of PIR-PUR/DMMP system can be reasonably deduced as follows: The foaming agent gradually changes from liquid to gaseous during the foaming process of PIR-PUR,which exists in the bubble wall of PIR-PUR.After foaming,the temperature of polyurethane material decreases rapidly.the strength of PIR-PUR decreases with the increase of DMMP content.Due to the thermal expansion and cold shrinkage,the air pressure in the bubble decreases,and the bubble shrinkage gradually under the action of shrinkage stress.With the passage of time,under the action of stress,the soft segment of PIR-PUR polymer began to move gradually,so that its shape was gradually restored.