Rheological study of polypropylene irradiated with polyfunctional monomers H. Otaguro a , S.O. Rogero a , A. Yoshiga a , L.F.C.P. Lima a , D.F. Parra a , B.W.H. Artel b , A.B. Luga ˜o a, * a IPEN/CNEN – Instituto de Pesquisas Energe ´ticas e Nucleares, Av. Professor Lineu Prestes, 2242, CEP 05508-000 – Cidade Universita ´ ria, Sa ˜o Paulo, SP, Brazil b EMBRARAD – Empresa Brasileira de Radiac ¸o ˜es Ltda, Av. Cruzada Bandeirante, 269, CEP 06705-140 – Cotia, Brazil Available online 5 September 2007 Abstract The aim of this paper is to investigate the rheological properties of polypropylene (PP) modified by ionization radiation (gamma rays) in the presence of two different monomers. The samples were mixed in a twin-screw extruder with ethylene glycol dimethacrylate (EGDMA) or trimethylolpropane trimethacrylate (TMPTMA) with concentration in the range of 0.5–5.0 mmol. After that, they were irradiated with 20 kGy dose of gamma radiation. The structural modification of polypropylene was analyzed in the melt state by mea- suring melt flow rate (MFR), g* (complex viscosity) and G 0 (storage modulus) in the angular frequency range of 10 À1 to 3 · 10 2 rad s À1 . From the oscillatory rheology data, one could obtain the values of g 0 (zero shear viscosity) that would be related to the molar mass. All results were discussed with respect to the crosslinking and degradation process that occur in the post-reactor treatment to produce con- trolled rheology polypropylene. The resulting polymeric materials were submitted the cytotoxicity in vitro test by neutral red uptake methodology with NCTC L 929 cell line from American Type Culture Collection bank. All modified PP samples presented no cytotoxicity. Ó 2007 Elsevier B.V. All rights reserved. PACS: 81.05.Lg; 81.40.Wx; 81.65.Mg; 82.35.Gh Keywords: Gamma radiation; Isotactic polypropylene; Biocompatibility; Monomers 1. Introduction It is well-known that the production of different grades of polypropylene (PP) matching the market requirements has been attained by polymerizing monomer with advanced catalyzers resulting in linear chains and in a rel- atively broad molecular weight distribution. Nowadays, however, new catalyzers and processes are able to produce PP with large and narrow molecular weight distribution, as well as PP with short branches and even a minor level of long chain branches. For instance, the so-called visbreak- ing process is obtained by peroxide degradation of PP, resulting in a narrow molecular weight distribution. The reduction of molecular weight together with the reduction of molecular weight distribution yields a number of specific advantages regarding the processability and final proper- ties of the PP product. Nevertheless, this process increases the costs due to the extra infra-structure, energy and perox- ides used [1–6]. On the other hand, there is still a need of PP with spe- cific structural features in order to cope with the increasing requirements from the market. Radiation processing of PP has been utilized to produce PP with a combination of spe- cial properties. For instance, the so-called HMSPP (high melt strength polypropylene) produced by radiation- induced grafting presents a structure composed of long 0168-583X/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2007.08.052 * Corresponding author. Tel.: +55 11 3816 9341; fax: +55 11 3816 9325. E-mail address: ablugao@ipen.br (A.B. Luga ˜o). www.elsevier.com/locate/nimb Available online at www.sciencedirect.com Nuclear Instruments and Methods in Physics Research B 265 (2007) 232–237 NIM B Beam Interactions with Materials & Atoms