Abstract
Phenol‐based novolac resins were synthesized with different mole ratios of phenol‐to‐formaldehyde. These novolac resins were epoxidized with molar excess of epichlorohydrin at 120 °C in basic medium. Novolac and epoxy novolac resin were characterized by FTIR, NMR and GPC analysis. Molecular weight was found to be 838. The epoxidized novolac resins were separately blended with different weight ratios of carboxyl‐terminated polybutadiene liquid rubber ranging between 0‐25 wt % with an interval of 5 wt %. All the blends were cured at 150 °C with 40 wt % polyamide. The cured films of blend samples were checked for use them in coating applications.
Highlights
Epoxy resins are widely used as high-performance protective coatings, structural adhesives, low-stress IC encapsulants and matrix resins for composites
Rubber was added to the uncured epoxy resins and after the cross-linking reactions the rubber-modified epoxy resins exhibited a two-phase microstructure consisting of relatively small rubber particles dispersed in a matrix of epoxy
Dynamic scans were recorded with a Perkin–Elmer differential scanning calorimeter (DSC) (Model Dymaond DSC; Switzerland) at a heating rate of 10 0C / min in inert atmosphere up to a temperature of 170 0C to get the cure temperature
Summary
Epoxy resins are widely used as high-performance protective coatings, structural adhesives, low-stress IC encapsulants and matrix resins for composites When cured these resins are highly cross-linked and become amorphous thermosets. Many authors[9,10,11] have made comments on the increasingly wide use of rubber modified epoxy resins as structural adhesives and as the matrix for fiber composites Because of their properties, epoxy resins have many commercial applications. Free-formaldehyde content was checked after every 45 min to check the progress of the methylolation reaction[16] These phenol based novolac- type phenolic resins were epoxidized by a method similar to the method given in literature[17] with epichlorohydrin in basic medium for a period of 5 h at 120 oC. Tp: Maximum temperature of exothermic peak. ccure time without curing agent; dcure time with polyamide
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