Molecular and mechanistic aspects of the functionalization of polyolefins with ester groups

In the present paper the functionalization reaction of polyolefins in the melt with diethylmaleate (DEM) in the presence of peroxide is revisited. The process was analyzed on the basis of several experiments carried out in the Brabender mixer with 30 min residence time and at constant temperature, 190° C for EPR and 200° C for LLDPE samples, while varying the number of branching in the starting polyolefin, the amount of DEM and of dicumyl peroxide (DCP). For reference purposes similar experiments were also examined as performed with EPDM and isotactic polypropylene (PP). At the end of the reaction, the polymeric product was treated with boiling acetone to remove low molecular weight products. In general, the acetone insoluble polymer was soluble in heptane and the functionalization degree (FD) referred to this fraction was in the range 0.2-2.0% mol of DES groups per 100 moles of monomelic units. The contemporary occurrence of the degradation and chain extension, including crosslinking reactions, provides a reasonable explanation of the results obtained. The analysis of the process performed in the present work helps to select proper conditions for controlling the characteristics and FD of the polyolefin and keep undesired secondary reactions under control