A structural polymer insert. The insert includes a substrate having a surface and an adhesive with the substrate being an admixture of a polypropylene component and a glass fiber component. The surface has a plurality of oxygen atoms, optionally introduced by air plasma, in an amount of 1 to 60 atomic percent of all the atoms present on the surface. The foam adhesive is attached to the surface through one or more reactive moieties resulted from oxidative action of the oxygen atoms.