Post-polymerization polyolefin modification by irradiation and chemical reaction

ENRIQUE VALLÉS

Río de Janeiro

Congreso; World Polymer Congress Macro 2006; 2006

Polyolefins are macromolecular alkanes and include some of the most familiar commercial plastic materials like polyethylene, polypropylene and their copolymer derivatives. The low cost of these materials, combined with their diverse and desirable property profiles drive large-scale production. However, the continuous necessity of generating new materials with wide ranging applications has motivated diverse attempts to convert some of these plastics into valueadded materials. Polymer modification constitutes a common alternative to obtain new materials with different attributes. Research and industrial approaches in this area dedicate a considerable amount of effort to find appropriate methods to improve mechanical, thermal, surface or rheological properties of commercial polymers. Crosslinking, scission and functionalization reactions are the three main ways available to alter the molecular structure of postpolymerized materials in order to expand their range of applicability. The insertion of a considerable amount of junction points between chains in a crosslinking reaction, increases the degree of branching, the molecular weight and the complexity of the molecular structure, leading eventually to an infinite network. This induces drastic changes in the rheological behavior and the final material properties. On the other hand, scission reactions introduce random cuts in long polymer chains, diminishing their length and molecular weight and improving their flow-ability. Both procedures are used in different industrial processes to modify properties of commercial polymers. Also, the grafting of functional groups to polymer molecules affects several properties, like surface adhesion and compatibility with other materials, improving their range of applications. In our presentation we will describe different examples of polyolefin modification employing some of these processes. We will look to  xperiments aimed to understand the role of scission and crosslinking reactions from a fundamental approach, by studying the alteration of the molecular structure and physical properties of model polyethylenes by radiation and peroxide treatment. Also, a few cases of modification of commercial polymers by  unctionalizing agents will be presented.