Stabilization of EVA Hot-Melt Adhesives

EVA HMAs are widely used in the packaging and bookbinding marketplace due to their superior adhesion to most substrates, their versatility, and their ease of formulation. EVA — based HMAs degrade under high-temperature processing and application conditions. Degradation usually results in discoloration, viscosity changes, and skin formation. EVA HMAs can be effectively stabilized against discoloration and viscosity changes using AO-2 (Figs. 20 and 21).

V. CONCLUSIONS

The hydrocarbon-based raw materials used by the adhesives industry are prone to ther­mooxidative degradation. This degradation can occur during isolation, storage, com­pounding, and end use. Raw material degradation can affect the performance of the final adhesive formulation detrimentally. Raw materials that have been stabilized with effective stabilizers in the early stages of their production will have increased storage life while maintaining consistent quality. Effective stabilization of the raw materials will result in an adhesive formulation with improved physical properties. The use of antioxidants only in the final formulations cannot ‘‘reverse’’ the effect of using predamaged unstabilized raw materials. The performance of the final adhesive formulation can be improved sig­nificantly by the further addition of effective antioxidants. Selection of the most effective antioxidant system to meet the performance demands will produce an adhesive that will maintain its physical properties during storage, compounding, and end use.

ACKNOWLEDGMENTS

The authors would like to thank CIBA-GEIGY Corporation, Ardsley, New York, and CIBA-GEIGY Ltd., Basle, Switzerland, for permission to publish this paper.

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