Non cross-linked modifiers for thermoplastic alloys comprising from 20 to 80% by weight based on the modifier of an interpolymer of ethylene and an alpha-olefin having from 4 to 12 carbon atoms grafted with an acid functionality, preferably maleic anhydride, having a Melt Index of from 0.3 to 100 and a density of 0.85 to 0.91 prior to being grafted and from 80 to 20% by weight of an ungrafted diene containing interpolymer derived from ethylene and an alpha-olefin having from 3 to 12 carbon atoms and an amount of a cross-linking component effective to provide cross-linking during subsequent melt blending with a condensation polymer having a melting point of at least 150° C.