Investigations into the Chemical Modification of Polyolefin Surfaces by Radical Reactions during Molding Ju ¨rgen Nagel, * Rene ´ Brunotte, Bernd Hupfer, Karina Grundke, Dieter Lehmann, Gu ¨nter Mennig Introduction Polyolefins are widely used for the production of plastic parts because of their good material properties and the low costs. The ongoing demand of the complexity of parts has resulted in the combination of different materials, for example by bonding or surface finishing. The disadvantage of polyolefins is their low polarity, which makes it difficult to combine them with other materials. Commercially, this is overcome by surface pre-treatment, usually by flame, corona or plasma, [1] where nonpolar groups of the polyolefin are converted to functional groups. [2,3] These processes of surface modification have the following disadvantages: due to the high energy applied, the types of functional group created on the surface are very diverse; the effect is often not permanent; and, generally, they require an additional step in the processing chain. An advanced approach is the grafting of polar groups onto the polyolefin surface. [4] Grafting of functional polymers results in a permanent modification. [5] However, all grafting methods have to be done in separate processing steps. Attempts are made to overcome these problems. However, neither grafting of the bulk with polar groups nor copolymerization with polar monomers improves the surface properties in a way that straight bonding or painting can be carried out without further pre-treatment that retains the bulk properties. [6,7] Surface-reactive injection molding is a different approach to produce parts with modified surfaces. The Full Paper The surfaces of polyolefin parts are usually modified by separate processing steps. In this paper, we investigate how an in situ surface modification of polyolefins could be realized during molding, based on radical reactions, by which a macromolecule with functional groups is grafted to the polyolefin surface. The tempera- ture of the melt is used to initialize the reactions. The different steps of the radical reaction chain were analyzed using model reactions. A modifier composition consisting of dibenzoylperoxide, potassium persulfate and poly(vinyl alcohol) revealed to be suitable. This composition was used for injection molding experiments. The bondability of the injection molded parts was largely enhanced. J. Nagel, B. Hupfer, K. Grundke, D. Lehmann Leibniz Institute of Polymer Research Dresden e.V., Hohe Straße 6, 01069 Dresden, Germany Fax: 00-49-351-4658-290; E-mail: nagel@ipfdd.de R. Brunotte, G. Mennig Chemnitz University of Technology, Reichenhainer Straße 70, 09126 Chemnitz, Germany 480 Macromol. React. Eng. 2007, 1, 480–487 ß 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim DOI: 10.1002/mren.200700009