Rheology of epoxy networks near the gel point

Summary Curing and gelation of diglycidyl ether of Bisphenol A with poly(oxypropylene)-diamine (Jeffamine D 400) was followed using dynamic mechanical measurements. The gel point was determined rheologically and the characteristic value of the loss factor tan at the gel point, (tan)_gel, was found to depend on the structure of the polymer. A negative normal force is generated in the shear dynamic mechanical measurement at the gel point.Dedicated to Dr. Karel Duek on the occasion of his 60th birthday for his important contribution to polymer science