21 июля, 2015 
Malyar It has been demonstrated that the hydrocarbon-based raw materials of an adhesive formulation do undergo thermooxidative degradation and that the addition of antioxidants is necessary to maintain the integrity of these components during storage and compounding. In this section we illustrate the effects of using unstabilized raw materials in adhesive formulations in comparison with stabilized raw materials.
1. EVA Hot-Melt Adhesives
The effects of storage time of an unstabilized and a stabilized rosin ester tackifier on the properties of an EVA HMA are illustrated in Figs. 15-17. Significant effects on the initial color of the EVA HMA (Fig. 15) are observed when using an unstabilized tackifier. An increased level of hydroperoxides is also noted. In this situation, the addition of an antioxidant to the HMA will not correct the problem. However, the addition of an antioxidant to the HMA may reduce further discoloration during compounding or end-use applications.
Figure 16 illustrates the effects of an unstabilized tackifier on color formation as a result of high-temperature aging of the EVA HMA formulation. In this scenario the tackifier was aged for 18 days at 50° C and then combined with the other components at 177°C (350°F). The final HMA formulation was then aged at 170°C (338°F). Use of the unstabilized tackifier results in a darker initial color and a more rapid rate of discoloration than that of HMA using the stabilized tackifier.
A consistent viscosity of the EVA HMA during high-temperature aging can be achieved using a stabilized tackifier (Fig. 17). The EVA HMA usig the unstabilized
tackifier has a higher initial viscosity and a more severe increase in viscosity during aging than those of the EVA HMA prepared with the stabilized tackifier.
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