The effect of allylation degree on processing properties, thermal cure, and thermal properties of BMAN resins

A series of allyl-functional novolac (AN) resins with various allylation degree, from 32.4 to 114.6%, were synthesized and blended reactively with 4,4′-bismaleimide biphenyl methane (BMI) at a weight ratio of 2.50 : 1 to get BMI-modified and allyl-functional novolac (BMAN) resins. Structural characteristics of the resins were determined by Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance (1HNMR) techniques. Processing properties of BMAN resin system was evaluated by solubility, rheology, and thermal gelation, and the results show that processing properties of BMAN resins were excellent and could be tailored by changing allylation degree of AN resins. Differential scanning calorimetry (DSC) was used to evaluate cure reactivity of BMAN resin system, and the results reveal that the resins with higher allylation degree possessed better cure reactivity. Thermal properties were evaluated by means of dynamic mechanical analysis (DMA) and thermogravimetry analysis (TGA) techniques. The results reveal that with increase in allylation degree of resins the thermal stability of BMAN resins increased because of increase in crosslinking density, but char-yields of the above resins at 800°C decreased in turn. Understanding of the relationship between allylation degree and properties of the resins would be useful to direct the design of material to meet different requirements of applications. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007