“Effect Of Vacuumm Gamma Radiation On Metallocenic Propylene - 1-Hexene And Propylene - 1-Octadecene Copolymers”

A.J. SATTI; N.A. ANDREUCETTI; R. QUIJADA; E.M. VALLÉS

Lima, Peru

Congreso; SLAP-2008 "XI Simposio Latinoamericano y IX Congreso Iberoamericano de Polímeros"; 2008

Pontificia Universidad Católica del Perú

Propylene/α-olefine copolymers made with metallocene catalysts show well defined structures, homogeneous comonomer distribution and narrow polydispersity if compared with copolymers obtained by Ziegler–Natta catalysts. The introduction of a α-olefine comonomer during polymerization induces the insertion of short chain branches of a desired length in the growing chain. This procedure allows the synthesis of a wide variety of copolymers which have a potentially wide range of applications. For several purposes, like for example sterilization for medical and packaging applications, or to improve processing and terminal properties, high energy radiation is employed.  In this work we focus on the properties of gamma irradiated metallocenic isotactic polypropylene (iPP) and their α -olefin copolymers (α-OC) reported in table 1. These polymers were irradiated with 60Co gamma rays on vacuum in order to minimize scission of the polymer chains. The changes introduced by radiation on the molecular structure and the physical properties of the α-OC were studied by different techniques. Molecular weights were measured employing gel permeation chromatography with refractive index (RI) and light scattering (MALLS) detectors. Possible chemical changes were analyzed using Fourier transform infra-red spectroscopy (FTIR). Thermal properties were measured by Differential Scanning Calorimetric. The gel contents were determined by extractions with boiling xylene and the viscoelastic properties - elastic G′ and viscous G″ modulus - were measured in a rheometer in small-amplitude oscillatory shear flow as a function of frequency and temperature.