Study On Epoxy/Nitrogen-containing Flame Retardant Curing Agent System

Epoxy resin (EP) has been widely used in the fields of mechanics, electronics, air and spacecraft because of its outstanding performances. A copper clad laminate made of bromized epoxy (BEB) dominates the field of printed circuit board (CCL) for its excellent flame retardance. However, it was discovered that the application of halogenated flame retardant (FR) had been limited because BEB gave off toxic gases such as HBr in the combustion and resulted in serious pollution to the environment. It's urgent to develop a novel FR without halogen to satisfy the requirments of flame retardance and environmental protection. On the basis of analyzing the previous work, the route of Nitrogen-containing compounds modifying BPA-Novolac used as curing agent of epoxy resin was adopted to satisfy the flame retardant requirements. The main contents include:1. Design and synthesize two type of nitrogen-containing bisphenol A novolacs based on the reacting mechanism of phenolic resinsTwo types of nitrogen-containing prepolymer solutions are synthesized from melamine, urea and formaldehyde. The effect on reaction rate and structure of prepolymer solutions is discussed. The results indicate that at temperature of 50℃ to 70℃, at pH of 7 to 9, stabilizing and transparent prepolymer solutions can be abtained.BPA-Novolacs modified by MF, UF are synthesized by the reaction of BPA, formaldehyde with MF, UF. The effects on soft point are discussed. It is discovered that by means of controlling pH value of medium from 7 to 9, adding MF, UF near to terminating time, gel problem can be basically solved. Higher Nitrogen-containing retardants can be synthesized with relatively low soft point between 120°C ~ 130°C.2. Characterization of nitrogen-containing BPA-NovolacsTwo types of Nitrogen-containing BPA-Novolacs have been characterized by Differential Scanning Calorimeter (DSC), Flourier Transmit Infrared(FTIR). The results indicate that the synthesized resins have a good thermal stability. The temperature of decomposition is from 260°C to 290℃. The FTIR spectra indicate the nitrogen-containing phenolic resins are in accordance with the design.