with the curing agent 1 1 equivalent ratio at 150 u00b0 c with stirring and the well mixed molten mixture was poured into a hot aluminum mould cured in an oven at 170 u00b0 c for one hour and then postcured at 200 u00b0 c for two hours the dynamic mechanical analysis dma properties of the resulting cured epoxy resins are shown in table 8 the thermogravimetric analysis data thereof are shown in table 9 and the flame retardant properties thereof are shown in table 10 it can be seen from table 8 that the cured epoxy resins of the present invention have glass transition temperatures tg about higher than those of the conventional bisphenol a cured epoxy resin and the conventional flame retardant tbba cured epoxy resin the data in table 9 show that the cured epoxy resins of the present invention have a better thermal stability and higher char yield than those of the conventional flame retardant tbba epoxy resin cured by phenol formaldehyde novolac resin pn the data in table 10 indicate that the cured epoxy resins of the present invention have excellent flame retardant properties especially no fume and dripping occur in the combustion test and thus is very suitable for use in the semiconductor encapsulation applications the flame retardant epoxy resins containing the phosphorus containing rigid group odopm bonded to bpa bp and sdp disclosed in the present invention can be used to prepare flame retardant cured epoxy resins having improved thermal properties and flame retardancy as shown in tables 8 to 10 the presently disclosed embodiments are therefore considered in all respects to be illustrative and not restrictive the scope of the.