Preparation,Combustion And Numerical Simulation Of Flame Retardant Rigid Polyurethane Foam

In recent years,polyurethane foam insulation materials have been widely used in construction,aviation,automobile manufacturing,transportation,medicine,agriculture and other fields due to their excellent thermal insulation and waterproof properties.However,polyurethane foam has the characteristics of extremely easy ignition,rapid fire spread,large amount of smoke and strong smoke toxicity,which causes frequent occurrence of polyurethane building fire accidents,resulting in huge property losses and casualties.Therefore,how to reduce the fire hazard of polyurethane foam,reveal the burning law of polyurethane foam,and fundamentally control the spread and expansion of fire,has become a hot topic of current research.Therefore,it is of far-reaching practical significance to develop flame-retardant polyurethane foam and provide theoretical reference for polyurethane foam fireproof design.In this paper,the pyrolysis and fire propagation characteristics of self-made rigid polyurethane foam and flame-retardant rigid polyurethane foam were compared.The pyrolysis characteristics such as weight loss and activation energy of materials at different heating rates and different environmental atmospheres were studied.Through the experiment of small and medium size fire spread on polyurethane foam,the changes of parameters such as flame structure characteristics,fire spread speed,flame temperature and mass loss rate were analyzed,and the combustion and fire propagation of polyurethane materials with different flame retardants were revealed.the difference.Finally,the numerical simulation of FDS was carried out to study the double-sided combustion and fire propagation characteristics of rigid polyurethane foam at different placement angles.The simulation results proved the experimental phenomenon well.In addition,the fire propagation characteristics of flame retardant polyurethane foam were explored.Numerical simulations have enriched the study of fire characteristics of polyurethane foams.Firstly,a flame-retardant and non-flame-retardant rigid polyurethane composite was prepared by one-step synthesis method,and the pyrolysis behavior and pyrolysis of polyurethane materials in two atmospheres?Nitrogen,Air?by synchronous thermogravimetric analyzer?TG?.Kinetic parameters?thermal weight loss rate,decomposition temperature,activation energy,etc.?,as well as char formation,were analyzed.It is found that with the increase of heating rate,the reaction moves to the high temperature zone,the main reaction zone gradually increases,and the maximum thermal weight loss rate increases gradually.There are two main weight loss stages in the air atmosphere under both flame retardant and non-flame retardant rigid polyurethanes.However,there is only one major weight loss stage in the nitrogen atmosphere.The initial decomposition temperature of the samples from low to high is RPUF/EG<RPUF<RPUF/AHP.When using KAS and OFW methods to obtain the activation energy of three polyurethane samples is:RPUF/AHP<RPUF<RPUF/EG in air atmosphere and RPUF/AHP<RPUF/EG<RPUF under nitrogen atmosphere.The addition of expandable graphite and aluminum hypophosphite can increase the carbon content of the sample.Under the air atmosphere,the char formation rate of the sample at 800?is much lower than that under the nitrogen atmosphere.Then,through the establishment of a small and medium-scale experimental platform,using advanced equipment such as thermocouple,infrared thermal image,and heat flow meter,the flame retardant and non-flame retardant rigid polyurethane composite material in horizontal and vertical situation of two-sided combustion and fire spread characteristics were studied.The study found that during the fire spread process,carbonization occurred on the surface of the material,and there were unburned materials inside.At the same time,the sample RPUF/AHP5?Contains5wt%aluminum hypophosphate?showed extinguishing after a period of fire spread in either horizontal or vertical conditions.This is mainly due to the oxidation of the phosphine gas decomposed by the flame retardant AHP at a high temperature to form a phosphorus-containing compound such as phosphoric acid or metaphosphoric acid to promote the formation of charcoal in the polyurethane molecular chain,and finally the flame is extinguished.In the case of horizontal double-sided fire propagation,the specimen with the addition of expandable graphite?EG?has the most obvious bending deformation,and the bending deformation of RPUF/EG10 is significantly higher than that of RPUF/EG5,which is mainly caused by the low strength of EG.Finally,the Pyrosim software was used to simulate the double-sided combustion and fire propagation characteristics of non-flame-retardant rigid polyurethane foam at0°?30°?45°?60°and 90°.The numerical simulation results of the sample at0°and 90°fire spread are highly consistent with the experimental phenomena.The results show that when the placement angle is 45°,the sample burns gently,and the mass loss rate and the heat release rate are relatively low.As the placement angle increases,the fire spread speed gradually increases,and the average fire spread speed varies with the placement angle according to the following formula:y?28?.131?10^-3x²-0.01527x?10?0.42109.In addition,the fire spread of flame-retardant rigid polyurethane foam was studied by numerical simulation,and the simulation results of flame retardant rigid polyurethane foam were obtained by modifying the activation energy,carbonization rate,flue gas productivity and other parameters.