Investigation On The Enhanced Flame Retardancy And Thermal Insulation Properties Of Polyurethane Foam

In recent years,China's energy consumption has increased dramatically,and building energy consumption accounts for about 30% of total energy consumption.The external wall insulation materials play an important role in building energy efficiency transformation.However,because the commonly used polystyrene and polyurethane foam insulation materials are highly inflammable.Phenolic foams are hard to burn,but the cost of preparation is high.Therefore,developing a refractory and low cost foam insulation material is imminent.Polyurethane foam is an important kind of synthetic-material.Polyurethane foam is applied in many fields such as thermal insulation due to its low thermal conductivity,low density and high specific strength.Aiming at blowing agent of HFC-365 mfc and water,the influence of different chemical composition of the foaming system on the properties of polyurethane foam was analyzed by changing isocyanate index and dosage of blowing agent.Get the optimum formula with which to produce excellent rigid polyurethane foam.In view of the weakness of low strength and poor fire resistance,the comprehensive properties of polyurethane foam are improved by adding diatomaceous earth and chopped carbon fiber respectively.The properties before and after the addition of diatomaceous earth and chopped carbon fiber were investigated,and the mechanism of improving the performance of the sample by different amounts of diatomaceous earth or chopped carbon fiber was analyzed.Polyurethane foam is an indispensable building material,but its flame-retardant performance is extremely poor and it will produce a gas containing highly toxic hydrogen cyanide after combustion.It has caused many major fire accidents,so it is extremely urgent to improve its flame resistance.The research has shown that the apparent density of foam samples increases with the addition of two fillers,but the overall increase is not large.The dimensional stability of the foam was improved after the addition of diatomaceous earth or chopped carbon fiber.The infrared spectrum analysis showed that the absorption peak position and area of the polyurethane foam before and after the filler addition did not change substantially,indicating that the addition of the filler did not change the structure of the polyurethane.Polyurethane does not undergo degradation and other chemical reactions.The thermal conductivity of the rigid polyurethane foam decreases with the increase of the amount of diatomaceous earth,and starts to rise at 15wt%,and the thermal conductivity is the lowest,which is about 15% lower.With the increase of the content of the two kinds of fillers,the compressive strength of the foam increased first and then decreased.When the mass fraction of diatomaceous earth and chopped carbon fiber reached 5wt% and 2wt%,respectively,the strengthening effect of the compressive strength of the foam reached the best.At the same time,it can be seen from the scanning electron microscope and super depth of field photograph of the foam sample that the addition of the two fillers makes the cell structure of the polyurethane foam more compact.The addition of the inorganic material diatomaceous earth also improves the flame retardancy of the foam to a certain extent.However,chopped carbon fiber does not contribute to the improvement of flame retardancy.