Blending in: how blended EVAs compare to reactor-grade EVAs in hot-melt adhesives

摘要

Formulators of hot melt adhesives (HMAs) sometimes use two or three different EVA grades instead of one For the most part blends are used because of the lack of single EVA grades with the desired viscosity, while in some cases, they are used to improve certain hot-melt properties. However, few reports on blend properties have been issued. In this report, several examples of blends having equivalent VA and MI levels to those of a single component were considered and their HMA properties compared. To demonstrate the significance of blending on HMA properties, a DOE (design of experiment) was performed employing the three-factor mixture design method. Blends, generally, gave comparable properties with those of their single-component counterparts. However, T-peel strength and lap joint shear strength were noticeably higher, while the open time and the set time tended to be longer. The thermal stability was generally a little poorer.