APAO polymers are used as a base for the manufacture of a wide variety of hot melt
adhesive and sealant systems. Because APAO is compatible with many solvents, tackifiers,
waxes, and other polymers, it is well suited for many adhesive applications in the
packaging, construction, medical, and personal care industry. As an example, APAO
hot melt adhesives are widely used for hygienic applications in the adhesive industry
such as disposable diapers.
Similar to styrene-isoprene systems, APAO polymers degrade via chain scission during
high temperature aging. The appropriate choice of antioxidant or antioxidant system
can prevent the effects of degradation such as color formation and most importantly,
viscosity decrease. (Figures 1-4) Depending on the adhesive system and application
requirements, the use of lactones may provide further stabilization benefits.
Dynamic Aging at High Temperatures
Figure 1 : Gardner Color of APAO-HMA after Aging at 200°C
Figure 2 : Viscosity of APAO-HMA after Aging at 200°C
Static Aging at High Temperatures
As seen in Figure 3, the use of a phosphite in conjunction with the primary antioxidant
improves the long-term color stability of the APAO hot melt adhesive.
Figure 3 : APAO-HMA Color After Aging at 170°C
Figure 4 : APAO-HMA Viscosity After Aging at 170°C