Reometryczne badania procesow sieciowania polietylenu i kopolimerow etylenu wobec nadtlenkow. Cz. II. Porownanie przebiegu reakcji sieciowania PE-LD, PE-LLD i kopolimeru etylen/octan winylu

Abstract

Methods of checking and valuation of the course of polyolefin plastics crosslinking processes, described in the literature (mainly rheometric one, as well as based on the swelling factor or gelation number) were presented. Kinetic principles of the problem investigation by rheometric method were discussed. Heat effects of the processes of PE-LD, PE-LLD or ethylene/vinyl acetate (E/VAC) copolymer crosslinking were determined using DSC method. Dependencies of torsional moment in rheometric measurements (M) and gelation number on crosslinking time were also determined and an agreement in these dependencies courses has been found. The rates of PE-LD, PE-LLD and E/VAC crosslinking processes in the presence of dicumyl peroxide have been studied using rheometric method. On this basis the constants of relative rates of M changes during the reaction as well as activation energies of the crosslinking process in the conditions of rheometric measurements, carried out in the range of temperature 170-200 °C, were determined. Activation energies determined this way let compare the crosslinking abilities of the polymers investigated. The ratio of the result of maximal and minimal torsional moment values subtraction and torsional moment minimal values [(M m a k s - M m i n )/M m i n ] decribes the polymer crosslinking degree.