Addition-cure phenolic resins based on propargyl ether functional novolacs: synthesis, curing and properties

Thermosetting phenolic resins, bearing varying extents of propargyl ether g roups (PN resins), have been synthesized by the Williamson reaction of a no volac with propargyl bromide and the products characterized. The resin prec ursors were cured through Claisen rearrangement of the propargyl ether grou ps and thermal polymerization. The activation energy for thermal cure is su bstantially lower than that of model bispropargyl ether compounds but is qu ite independent of the degree of functionalization. The isothermal cure pro file, extrapolated from non-isothermal DSC kinetics studies is consistent w ith the results from DMA studies. The mechanical properties of glass compos ites of the resins, of varying propargyl contents, reveal good consolidatio n of the interphases, evident from the initial gain in both interlaminar sh ear strength (ILSS) and flexural strength. The benefits of better resin-rei nforcement interactions are not retained on crosslinking the resin further, wherein the composite fails by a combination of fibre debonding and brittl e fracture of the matrix. Although the resins show better thermal stability than cured resoles, a higher extent of propargylation is detrimental for t he thermal stability. Resins with moderate propargylation show good mechani cal and thermal properties. (C) 2001 Society of Chemical Industry.