Study On Preparation And Modification Of Intumescent Flame Retardant Rigid Polyurethane Foam Coating

Rigid polyurethane foam（RPUF）has been used as thermal insulation materials due to its closed cell structure and excellent low thermal conductivity.However,it is very easy to burn when encountering ignition sources,and generates a lot of heat,smoke and drops,occasionally causing serious casualties and property losses.At present,the main way to solve the problem of RPUF flammability is to directly add phosphorus,silicon,nitrogen and other flame retardants or reactive flame retardants.The former is easy to change the physical structure of foam materials by adding a large number of flame retardants,while the latter is complex and costly.Therefore,based on the requirements of the practical application of RPUF and the requirements of the Fourteenth Five Year Plan and 2035 Vision,this paper designs an intumescent（IFR）flame retardant coating to be applied to the RPUF surface.The main work is as follows:（1）In the first part,the influence of intumescent flame retardant system on the properties of flame retardant coatings is discussed.Firstly,the low-cost silicone acrylic lotion was selected as the base material of the flame retardant coating lotion.Through the vertical combustion experiment（UL-94）and the cone calorimeter test（CCT）,it was determined that when the content of silicone acrylic lotion was 25%,its flame retardant effect was the best.Then,through orthogonal experimental design and analysis,the optimal ratio of the intumescent flame retardant system was optimized:ammonium polyphosphate（APP）:pentaerythritol（PER）:melamine（MEL）=7:3:4.It can be observed through scanning electron microscope（SEM）that the pore structure of foam was well covered,so as to more effectively block the transfer of heat and smoke,The peak heat release rate（PHRR）and total heat release（THR）of the coated RPUF were significantly lower than those of the pure RPUF.The analysis of carbon residue shows that the dense carbon layer has a good shielding effect.（2）In the second part,the modified montmorillonite（APTES-MMT）was prepared with montmorillonite（MMT）as the substrate,silane coupling agent KH550（APTES）as the modifier,and methanol solution as the solvent.The influence of inorganic fillers on its flame retardancy was explored.APTES-MMT,aluminum hydroxide（ATH）,and titanium dioxide（Ti O₂）were selected as the research objects to conduct a single factor experiment.The thermogravimetric analysis（TGA）test showed that,the order of thermal degradation performance of coatings containing different inorganic fillers is APTES-MMT>ATH>Ti O₂.Through the vertical combustion experiment and mechanical property test,the results show that the performance of the expanded coating with filler has been further improved.（3）In the third part,based on the previous experiments,the influence of the synergistic effect of the three fillers on the ignition time of the composite expansion coating was discussed.Through the orthogonal experimental design analysis,the best proportion of the three fillers with the best flame retardancy effect was determined.In the limiting oxygen index experiment,the LOI of the samples coated with the composite expansion coating is more than 27%.In the vertical combustion test,the coated RPUF can extinguish rapidly.On the one hand,the flame retardant system of APP-PER-MEL can form an expanded carbon layer at high temperatures,which inhibits the spread of flame.On the other hand,under the synergistic effect of APTES-MMT and ATH,when their dosage is 5 wt.%and 6 wt.%respectively,the HRR,THR and total smoke（TSP）of RPUF are significantly reduced.