Polyolefin-polyamide blends by reactive extrusion
Résumé
Recent developments in reactive blends of various polyethylenes and polyamides carried out in melt processing focused on the combined radical reactivity of peroxide and monomer, leading to high levels of reciprocal grafting at the interface. The corresponding reactive blends were made in a co-rotating twin screw extruder (ZSK 30) in one single step. The present work deals with two different blends: polypropylene/polyamide (PP/PA6) and ethylene-propylene rubber copolymer/polyamide (EPR/PA6). The induced reactivity is based on a mixture of a peroxide (Perkadox 14) and a reactive monomer (maleic anhydride). The results confirmed that in both cases a good level of reciprocal grafting occurred between the olefinic and the polyamide materials. Moreover, it appears that if the resulting blend made of PP and PA6 exhibited good adhesion, the final mechanical properties were affected by the molecular weight degradation related to the β-scission in the presence of free radicals. On the other hand, the EPR/PA6 reactive blends showed a very finely dispersed phase of the elastomeric copolymer (particle diameter less than 1 μm) which corresponded to a very high level of impact resistance.