Study Of Carbon Foam From Ally COPNA-BMI Copolymer Resin

Aiming at the problems generated from the production of carbon foam such as poor mechanical strength, high cost, complex technology, difficult moulding and other issues,4,4’-bismaleimidodiphenyl methane (BMI) was copolymerized with allyl condensed polynuclear aromatic (COPNA) resin used as a precursor of carbon foam, which was prepared by performing a series of procedures including casting molding and atmospheric pressure pyrolysis. The structure changes and chemical compositions of the allyl COPNA-BMI copolymer resin during pyrolysis were studied. In addition, the foaming mechanism, structure features and physical properties of resultant carbon foams were investigated.Pyrolysis behavior of the allyl COPNA-BMI copolymer resin was studied by SEM, FT-IR, TG-DTG, Raman and elemental analysis. Results show that carbon foam can be directly prepard by pyrolysis of the copolymer resin, due to its self-foaming characteristics at high temperatures. The copolymer resin has an initial decomposition temperature of 300℃, a terminal pyrolysis temperature of 600℃ and the maximum decomposition rate temperature of 415℃. The resultant pyrolysis product has increasing C/H ratio with increasing pyrolysis temperature and meanwhile its crystalline structure is improved.Structures and properties of the carbon foams, which were prepared at 900℃ by pyrolysis of the allyl COPNA-BMI copolymer resins with different mass ratios of allyl COPNA resin to BMI, were studied using SEM, XRD, Laser thermal conductivity meter, and electronic mechanical universal testing machine. Results show that the carbon foams have similar crystalline structures and their pore sizes and porosity decrease with an increase in BMI content, wheras their properties including mechanical strength, electrical conductivity, thermal conductivity, bulk density and char yield increase. When the mass ratios of allyl COPNA resin to BMI varies from 1:0.8 to 1:1.1, the compressive strength, bulk density, electrical conductivity, thermal conductivity, bulk density and char yield of the carbon foam increase from 0.9 to 2.4MPa,4.3 to 10S/cm,0.31 to 0.44W/m·K,0.18 to 0.25g/cm3 and 34.21 to 39.26%, respectively, but its porosity decreases from 91.4 to 80.2%.The influences of high-temperature treatment on the structures and properties of the carbon foams were investigated. Results show that the high-temperature treatment has great effect on the structures and properties of resultant carbon foam. As the temperature increases, the microcrystalline structure of the carbon foam is improved and thus its graphitization degree increases. When the high-temperature treatment varies from 900 to 2400℃, the compressive strength, electrical conductivity, thermal conductivity, bulk density and porosity of the carbon foam, prepared with an allyl COPNA resin to BMI mass ratio of 1:1.1, increase from 2.4 to 2.8MPa,10 to 34S/cm, 0.44 to 0.54W/m·K,0.25 to 0.26g/cm3 and 80.2 to 85.8%, respectively.