Preparation And Characterization Of Cyanate Ester Foam

Cyanate ester resin(CE) possesses a symmetrical and rigid mo lecular structure. The cured CE resins form a highly cross-linked network structure with triazine ring, which gives it high heat resistance, excellent mechanical propert ies, good processing manufacturabilit y and unique dielectric properties. Therfore, CE can be used as the matrix for preparing high temperature resistant foam plast ics due to its excellent comprehensive properties.In this paper, cyanate ester foams(CEF) with different chemical structures were prepared using prepolymerizat ion method via moulding foaming process by using bishpenol A dicyanate ester(BADCy), bishpenol E dicyanate ester(BECy) and tetramethyl bisphenol F dicyanate ester(TBFDCy) as main material, ditin but yl dilaurate(DBTDL) as catalyst, azodicarbonamide(ADCA) as chemical blowing agent, corresponding foams called A-CEF, E-CEF and F-CEF. Through studying the influence of reaction temperature on CE systems' rheological properties, the condit ions of preparat ion CEF were determined. Two kinds of compound foam were prepared by using BADCy/BECy system and BADCy/TBFDCy system with different mo lar ratio as matrix, corresponding foams called AE-CEF and AF–CEF, respect ively. We analyze and characterize the foams' chemical structure, cell structure, thermal propert y, mechanical property, dielectric property and flame retardant through kinds of analysis test ing methods. The effects of densit y and mo lecure structure on the propert ies of CEF were primarily studied.The results showed that cells of A-CEF with different densit ies were uniformly distributed and composed of close d-cells. The average cell size decreased with the increase in densit y. Closed cell content, dielectric constant and dielectric loss increased with the increase in densit y. Compressive modulus and compressive strength increased with an increase in foam densit y, and they had linear relat ionship with ?1.043 and ?2.204, respect ively. Glass transit ion temperature(Tg) of the A-CEF was 263 ? and 5% weight loss temperature(Td5%) was 344 ?. It reveales that CEF has a good thermal stabilit y and excellent mechanical property. Different mo leculer structure of CE has different reaction condit ion. The greater the chemical activit y of CE monomer mo lecules, the lower the react ion temperature. Tg, compressive strength, compressive modulus and thermal stabilit ies of the foams with different moleculer structure were improved with the increasing rigidy of the main chain. Flame resistance increases with the decreasing amount of H of CE molecules. When the amount of BECy increased, namely the more flexible chain segment in the mo lecular structure, Tg, flame retardance and strength of AE–CEF decreased, and the flexibilit y became greater. When the amount of TBFDCy increased, namely the more rigid chain segments in the mo lecular structure, Tg, flame retardance and strength of AF–CEF increased.