Study On The Preparation And Foaming Chemorheology Of Rigid Polyurethane Foam Using As Deep Cold-heat Insulation Material

Rigid polyurethane foam is often used as a heat insulation material because of its low thermal conductivity.But when its application is in deep cold environment such as liquefied natural gas?LNG?containment system and tank insulation or in fire-resistant environment,it is necessary to greatly improve the mechanical properties and flame retardant properties to obtain good comprehensive properties.Besides,The change of the polyurethane matrix during foaming process is a chemorheology process.Rheological characterization of foaming process is essential to optimize the formulation and processing technology,to understand the foaming process and to prepare high performance foam materials.In this paper,the reaction kinetics and rheological behavior of foam matrix were studied by means of differential scanning calorimetry and rheology.The related physical model was proposed and the foaming process was successfully simulated.On the basis of optimized the formula,the suitable flame retardant system was explored,and the flame retardant properties of the material was greatly increased without reducing the thermal insulation performance.By exploring a suitable long glass fiber reinforced technology,the rigid polyurethane foam with low thermal conductivity,high flame retardant and high strength was finally prepared.The main results are as follows:1.The reaction kinetics and rheological properties of the polyurethane matrix were studied by thermal analysis,infrared method and rheological method.The relationship between reaction and viscoelastic of the system is established.We innovatively proposed a Gel-Vitrification-Dual-Control model,which could precisely describe the reaction kinetics and evolution of rheological properties during reaction.Based on this model,we used Field Phase two-phase method to simulate the foaming process of a certain formula and the variation of termpature and the foaming rate were also investigated.The simulation results were in agreement with the experimental results.2.Based on the optimal formulation,the comprehensive performance of different kinds of flame retardant modified rigid polyurethane foam plastics was studied.It was found that Decabromodiphenyl Ethane?DBDPE?and antimony trioxide?Sb₂O₃?was an effective flame retardant composite for RPUF especially at an optimum mass ratio of DBDPE/Sb₂O₃ of 4:1.Besides,the thermal stability of the composite foam was studied by thermogravimetric analysis,and it was found that flame retardant composite was able to promote polyurethane crack into small molecular and increase the residual char.3.Long glass fiber with surface modified by KH550 was used to reinforce two kinds of flame retardant rigid polyurethane foams with different density.It was found that high density foam had a better reinforcement.The other properties of the materials were also investigated.The results showed that the flame retardant properties,mechanical properties and thermal insulation properties of the materials all reached a high standard for international certification standards of thermal insulation materials used in the protection system of LNG tanker.