The effect of the concentration of vinyl alcohol (VOH) groups in commercial poly(vinyl butyral) (PVB) on the adhesion of the polymer to glass beads in particle-filled composites is investigated. Both the optical single particle composite (SPC) and acoustic emission (AE) techniques were used to determine the applied uniaxial tensile stress at which a single imbedded particle was detached from the matrix. The results for the failure stress from the two techniques are consistent with one another and show that the adhesion strength is improved substantially as the vinyl alcohol content increases. The improved adhesion performance is attributed to an increase in condensation of hydroxyls within the polymer matrix and acid-base interactions between the hydroxyl groups on the bead's surface and those in the polymer. The AE results also provide details of the mechanism of the debonding event in cases of both weak and strong adhesion.