Monofilaments produced by modification of isotactic polypropylene with gamma irradiation

Abstract

One of the effective approaches to achieve high melt strength polymers (HMS) is to add long chain branches onto backbone species using gamma radiation. Grafting and branching result from macroradicals combinations during the irradiation process. Nonetheless, crosslinking and main chain scission in the polymer structure are also obtained. Due to the chemical nature of polypropylene (PP), it has a tendency to undergo β-scission which competes with grafting and crosslinking reactions. In order to decrease the degradation of PP and improve the degree of branching, various polyfunctional monomers had been used to obtain chain branching with lower doses. In this work, commercial polypropylene (iPP) with melt flow index of 10g/10min was irradiated with a 60Co source at doses of 12.5 and 20 kGy under acetylene to improve melt strength and drawability. The results of mechanical and rheological tests demonstrate that in the sample modified with dose of 20 kGy the predominant phenomena was degradation by chain scission and in the sample modified with dose of 12.5 kGy were branching and crosslinking. So the monofilament of this sample was produced and it was observed an increase of tenacity in relation to the PP pure.