Synthesis of chitosan-based flame retardant and its fire resistance in epoxy resin

A novel flame retardant CCD was synthesized by the condensation between cinnamalde and chitosan, followed by the addition reaction with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide(DOPO), and CCD was named from the initials of the three raw materials. The intermediate product CC and the target product CCD was then characterized by infrared spectrometry and elemental analysis. The flame retardancy of EP thermosets modified by CCD was dramatically improved. Epoxy resin (EP) with 10wt% CCD passed vertical burning (UL-94) V-0 rating and possessed limited oxygen index (LOI) value of 31.6 %. Cone calorimeter test exhibited the introduction of 3.5g CCD into 35g EP decreased the total heat release by 38.8 % and decreased the total smoke product by 72.0 %. XPS, FTIR, SEM and Raman tests were proceeded to determine the char residue for EP/10 % CCD thermoset, and the results showed that char residue for EP/10 % CCD thermoset possessed dense and compact structure which played a positive effect in blocking the exchange of heat and gas.