Study On Preparation And Modification Of Polyimide Annual Foam

In this paper,the synthesis technology and properties of polyimide foam are studied.Firstly,using BTDA and 4,4,ODA as raw materials,methanol and tetrahydrofuran as mixed solvents,a two-step method is used to prepare polyester ammonium salt powder.The polyester ammonium salt powder was foamed in a free-foaming form to obtain a soft open-cell polyimide foam;the polyester ammonium salt powder was subjected to thermogravimetric analysis to determine that the drying temperature of the polyester ammonium salt powder was 70 ° C.The foaming temperature is 160 ?,the powder particle size is screened to determine the final powder particle size is30-40 ?m;by controlling the drying time,powders with different residual solvents are prepared for foaming,and the foaming results are compared to determine the powder drying time;Three different types of foam stabilizers were screened out by experiments,and it was finally determined that SILOK2008 N foam stabilizers were used in an amount of 1.5% of the monomer mass.Fourier infrared spectroscopy,thermogravimetric analysis,scanning electron microscopy,and differential scanning calorimetry had been used to analyze and characterize the structure and performance of polyimide foam.We used a universal testing machine,thermal conductivity meter,and limiting oxygen index.The mechanical properties,thermal properties,and flame retardancy of the foam were tested by instruments and the like.The results show that the density of the prepared polyimide foam is 0.01 g / cm3,T5% is about 500 ?,and Tg is about 250 ?.The thermal conductivity is 0.035 W /(m K),the compressive strength is about 0.02,and the LOI value is 38.2%,which shows that it has good thermal stability,heat insulation performance and excellent flame retardancy.In the experiment,two kinds of inorganic fillers,vermiculite and graphite were used to modify and strengthen the foam.The vermiculite,expanded graphite and polyester ammonium salt powder in different parts(0%,2%,4%,8%,and 10%)were modified.After blending,foaming was performed,and then the structure,thermal properties,compression properties,and flame retardancy of the modified polyimide foam were characterized.The results showed that the introduction of the filler had no effect on the chemical structure of the foam.The flame retardant performance has been greatly improved,but the size of the filler has an influence on the cell size of the foam,which easily causes excessive cell size and uneven cell size.