The synthesis of polyolefin graft copolymers by reactive extrusion

摘要

The synthesis of polyolefin graft copolymers by reactive extrusion or other forms of melt phase processing is reviewed. Primary concerns are the structures of the graft copolymers formed, the mechanisms of graft formation, and their relationship to processing conditions. The first section addresses typical process conditions, mechanisms of free radical induced modification of polyolefins in the melt, and provides some general guidelines as to the factors important in controlling product structure. A critical review of the melt phase synthesis of polyolefins with reactive functionality follows. These materials, which may serve as precursors to other polyolefin graft copolymers, include polyolefins with grafted maleic anhydride, fumarate and maleate esters, (meth)acrylate esters [e.g. glycidyl methacrylate and hydroxethyl methacrylate] and (meth)acrylic acid. References to both the open and patent literature are provided. The use of reactive extrusion in interchain polymer formation is then considered. Methods include the transformation functional polyolefins into graft copolymers by opening of epoxide or anhydride, transesterification and related processes, and free radical induced coupling. A final section briefly details methods for characterising modified polyolefins.