Isotactic polypropylene (iPP) is a thermoplastic polymer, however, its use as an engineering plastic has been limited because of its poor impact toughness, and for improving that, appropriate elastomers are usually added to modify its toughness. In the present work, maleic anhydride grafted styrene-b-(ethylene-co-butylene)-b-styrene triblock copolymer (mSEBS) has been blended with iPP for investigating the interfacial effect on the toughness improvement. A normal mSEBS sample has been chosen to use to compare with an aged one (over nine-year aging time) for this comparison purpose. Our study shows that the aged one (as a type of waste) does not function well to toughen the iPP, whereas the normal one with no ageing functions well to improve the toughness of iPP blend. It is further disclosed that the interfacial interaction between mSEBS particles and iPP matrix plays a key role for this effect.