Monitoring partially-cured epoxy adhesives in disk-drive sub-assembly by thermal analysis (TA) techniques

Abstract

This paper outlines the technique and applications of using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) to monitor the degree of cure of process-cured epoxy adhesives with poor adhesion strength. Thermal events, such as residual cure and glass transition, detected by DSC analysis can be used to monitor insufficiently-cured thermal-curing adhesives. Both heat of residual cure and glass transition is directly proportional to the degree of cure or conversion from unreacted to reacted. Glass transition also governs the maximum operating temperature of the sub-assembly. The absence of residual cure of improperly-cured photo-curing epoxy adhesives during further exposure to heat makes it difficult to monitor these grade of adhesives by DSC. The weight loss profile of selected photo-curing adhesives by TGA can be used to qualify a photo-curing adhesive.