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In this paper the unequivocal determination of the structure of the functional groups inserted into polyethylene moieties is described. Detection of the CH(COOEt)CH2COOEt groups, grafted on the polymer backbone by reaction of molten HDPE with diethyl maleate and with dicumyl peroxide as the radical-generating species, is accomplished by comparative analysis of 13C NMR spectra of the functionalized polymer and two suitably synthesized model compounds: ethyl 3-carbethoxy-4-rc-propylheptanoate and ethyl 3-carbethoxy-4-n-hexyldecanoate.

The radical functionalization of different types of polyethylene, such as high-density (HDPE) and linear low-density (LLDPE) polyethylene, with diethyl maleate (DEM) as a polar functional monomer and dicumyl peroxide (DCP) as radical initiator was investigated, and conditions for obtaining a controlled degree of functionalization and a low amount of degradation products without crosslinking were determined. Attention was paid to achieve a moderate functionalization of the polymer, in order to limit the modification of the mechanical and physical properties of the polyolefins. The molecular weight distribution of some of these polyethylenes was only moderately affected by the functionalization reaction. A c r tical discussion of the results outlines the fundamental role of process parameters such as stirrirAg rate and heat exchange. 0 1992, Hiithig & Wepf Verlag, Basel CCC 0025-1 16X/92/$03.00

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