Reading an Epoxy Resin Grade Table Without Guessing

Epoxy Equivalent Weight Comes First

EEW is the mass of resin containing one equivalent of epoxy group, and it sets the hardener stoichiometry. Liquid bisphenol A grades such as NPEL-128 sit at 184 to 190 g/eq. Solid grades climb steadily: NPES-901 at 450 to 500, NPES-907 at 1500 to 1800, NPES-909 at 1800 to 2500 g/eq.

Liquid Semi Solid or Solid

Liquid grades are quoted on viscosity at 25 degrees C, typically 12000 to 15000 cPs for standard NPEL-128. Solid grades are quoted on softening point instead, from 64 to 74 degrees C for NPES-901 up to 130 to 150 degrees C for NPES-909. Semi solid grades such as NPEL-134 sit between the two.

Crystallisation Is a Real Problem

Standard liquid bisphenol A resin can crystallise in a cold warehouse and has to be remelted. Low crystallisation grades such as NPEL-128R and non crystallising grades such as NPEL-128S exist specifically to avoid that, and are worth the difference if your storage is unheated.

Electronic Grades Are Not a Marketing Label

NPEL-128E is a standard electronic grade and NPEL-128G carries low total chlorine at 1500 ppm or below. If the resin goes anywhere near fine pitch circuitry, the chlorine limit is the specification that matters.

When to Move Off Bisphenol A

o-Cresol novolac grades such as NPCN-701 to NPCN-704L at 190 to 230 g/eq give higher functionality for composites, coatings and moulding compounds. Bisphenol F and phenolic novolac grades such as NPPN-638S and NPPN-631 are specified where thermal and chemical resistance in laminates and filament winding is the constraint.

Diluted Grades Save a Step

Xylene diluted grades such as NPSN-301X75 and NPSN-134X80 arrive ready to formulate into solventborne coatings, which removes a dissolving step from your process.