Abstract
Freeze storage of adhesives has been an industry-wide practice for a long time. However, when the technique was applied to an epoxy adhesive, anomalous, but very useful results were obtained. Among other observations, the study showed that freeze storage changes the final properties of the epoxy. The epoxy was applied as an adhesive in the sealing of a component. Among adhesive candidates that were evaluated, the epoxy EA9396 was preferentially selected because it is amenable to room temperature cure and consequently it exhibits less stress and fracture upon cure. The formulation was frozen at −43 °C for different periods of time. A cure schedule consisting of 16 h at room temperature followed by two hours at 65 °C imparted shore D hardness of 80, shear strength of about 1800 psi and an extent of cure of 82% to the adhesive regardless of the length of the freezing time. Rheometry analysis of the thawed frozen formulation showed an anomalous trend whereby the pot life increased immensely in direct proportion to the duration of the freezing time. In this study pot life implies the working life after the frozen formulation is thawed. A pot life of 85 min was observed for samples cold-stored for three weeks. This method would offer advantages in applications requiring long pot and cold storage lives. This paper provides an insight into this phenomenon.
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