The itaconic acid (IA, Biochemistry-China) and dicumyl peroxide (DCP) were used to promote grafting reactions in polyethylene-co-octene copolymer (made by Dow with the trade name Engage) in the melt state. Some preliminary reactions were carried out in a small closed mixer reactor to study the AI to DCP ratio necessary to modify the EOC by the reactive extrusion process. The best performances of the grafting reaction were obtained with AI/DCP ratio of 4/1 (see scheme A in figure).
The properties of the AI-modified EOC were obtained with the thermal, rheological and adhesion tests on aluminium and the glass substrates by using DSC, Melt flow index and peeling tests (lap shear joints), respectively. Then the production with a co-rotating twin screw extruder having L/D=40 (with D=26 mm) of a masterbatch by using a medium fluidity EOC copolymer (MFI=5 at 190°C and 2,16 kg with the norm ISO 1133) with as high as content of AI (about 20% wt) was achieved. The content of AI grafted in the mixture is then checked with termogravimetric analysis (TGA), differential calorimetry and FTIR-ATR. The characterization results showed that the IA was totally grafted into the EOC in the melt state and no crosslinking reactions occurred during the extrusion process.
Then, the masterbatch was diluted in the melt state by extrusion processing into other polyolefinic copolymer having different properties and composition, such poly(ethylene-co-vinylacetate) (EVA), poly(ethylene-co-butene) (LDPE) and high fluidity EOC. The evaluation of the IA-modified EOC of the adhesion performance in the melt were studied by lap shear and 90° peeling tests (see figure B, C and D). Furthermore, IA-modified EOC was used as compatibilizer for mineral fillers in a poly(propylene-co-ethylene) copolymer by measuring the mechanical properties. The efficiency of the EOC modified copolymers with EOC was compared with other commercially available polyolefins grafted with MA (i.e. made from Dow Chemicals).
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