An improved plasticized polyvinyl chloride interlayer for laminated safety glass, and an improved method of manufacturing a laminated safety glass including such plasticized polyvinyl chloride containing film is disclosed. An improved functional silane adhesion promoter is utilized in such a manner so as to impact energy dissipation is maximized while structural integrity is maintained. The plasticized polyvinyl chloride interlayer is formulated so as to provide improved long term heat stability at service use temperatures.