Synthesis, characterization and properties of tetramethyl stilbene-based epoxy resins for electronic encapsulation

Abstract

Two novel tetramethyl stilbene-based novolac ( II and IV) were synthesized from 2,6-dimethyl phenol and chloroacetaldehyde dimethylacetal or chloroacetone, and then the resulted novolacs were epoxidized to tetramethyl stilbene-based epoxy resins ( III and V). The proposed structures were confirmed by FTIR, elemental analysis, mass spectra, NMR spectra and epoxy equivalent weight titration. The synthesized tetramethyl stilbene-based epoxy resins were cured with 4,4-diaminodiphenyl methane (DDM) and 4,4-diaminodiphenyl sulfone (DDS). Thermal properties of cured epoxy resins were studied using dynamic mechanical analyzer, differential scanning calorimeter, thermal expansion analyzer and thermal gravimetric analyzer (TGA). These data were compared with that of the commercial tetramethyl biphenol (TMBP) epoxy system. According to the experimental data, the order of T g for cured epoxy system is III>TMBP> V. The order of moisture absorption for cured epoxy system is V< III<TMBP. According to TGA, the 5% degradation temperatures in nitrogen atmosphere were in the range 370–377 and 397–412 °C for DDM and DDS curing systems, respectively. In air atmosphere, the 5% degradation temperatures were in the range 372–385 and 410–411 °C for DDM and DDS curing systems, respectively. The CTE is in inverse order with T g, therefore, III/DDS<TMBP/DDS< V/DDS.