39 ice | science Emerging Materials Research Isothermal Crystallization of Novel Polypropylene/Polyaniline-Grafted-Short Glass Fiber (PAn-g-SGF) Composites Cárdenas, Uribe, Silva, Rejon and Guerrero http://dx.doi.org/10.1680/emr.11.00006 Paper 1100006 Received 06/09/2011 Accepted 27/10/2011 Published online 31/10/2011 Keywords: composites & isothermal crystallization & polyaniline & polypropylene & short glass fibers ICE Publishing: All rights reserved 1. Introduction Polypropylene (PP) is a thermoplastic that can be transformed into useful products by a wide variety of processes, which combined with a suitable cost/performance balance becomes a major factor in its commercial success. The ease of moulding and the attractive strength, stiffness, chemical stability and the use of high temperatures of articles molded of PP have made injection-molding the largest processing route of PP. A unique aspect of PP products, as well as to other major thermoplastics, is the use of macromolecular orientation to develop enhanced properties, principally in fibers and films, constituting nearly one-half of the consumption (Ward, 1975, Varga, 1995, Dekker, 1999). Depending on the application, PP can include additional modifications to improve electrical conductivity, impact and wear resistance, flame retardance, heat-deflection temperature and color, made possible using some additives, fillers and reinforcements (Manias et al., 2001, Gilman et al., 2000). The selection of the filler utilized to reinforce PP is a critical task in designing and controlling the mechanical and thermal properties of the composite. In general, the filler influences the crystallization of α, β and γ forms and the dimensional distribution of spherulites (Lotz et al., 1996, Cao et al., 2010). Short glass fibers (SGFs) are the most common fillers that are used to improve simultaneously the mechanical properties and heat-deflection temperature of PP (López Manchado et al., Isothermal Crystallization of Novel Polypropylene/Polyaniline-Grafted-Short Glass Fiber (PAn-g-SGF) Composites Cintya Valerio-Cárdenas Research Fellow, Laboratorio de Nanopolímeros y Coloides, Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, Av. Universidad s/n, Col. Chamilpa, Cuernavaca, Mexico Angel Romo-Uribe Director, Laboratorio de Nanopolímeros y Coloides, Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, Av. Universidad s/n, Col. Chamilpa, Cuernavaca, Mexico Rodolfo Cruz-Silva Assistant Professor, Centro de Investigación en Ingeniería y Ciencias Aplicadas, UAEM, Av. Universidad 1001, Col. Chamilpa, Cuernavaca, Mexico Leonardo Rejon Senior Scientist, Instituto de Investigaciones Eléctricas, Calle Reforma113 Col. Palmira, Cuernavaca, Mexico Ruben Saldivar-Guerrero Research Engineer, Instituto de Investigaciones Eléctricas, Calle Reforma113 Col. Palmira, Cuernavaca, Mexico Isothermal crystallization kinetics of composites of isotactic-polypropylene (iPP) reinforced with polyaniline-grafted short glass fibers (PAn-g-SGF) were studied by differential scanning calorimetry (DSC). The concentration of PAn-g-SGF ranged from 10 to 30 wt%. Furthermore, a composite of iPP blended with 5% polypropylene-grafted maleic anhydride and 30 wt% PAn-g-SGF was also studied. DSC showed that the crystallization temperature of iPP, T c , was significantly increased by the microfiller. Isothermal crystallization results showed that the kinetics of neat iPP is well described by the Avrami model, with half-time crystallization τ 1/2 in the range of 3 to 22 mins. Regarding the composites, τ 1/2 was five times faster than neat iPP. Furthermore, the kinetics of crystallization was described by the Avrami model only at temperatures not too close to the respective crystallization temperature T c . That is, the PAn-g-SGF microfiller acted as nucleating agent was significantly accelerating the rate of crystallization of the composites. The rate of crystallization was even faster than when using only bare glass fibers. Hot-stage polarized optical microscopy showed transcrystallinity induced by PAn-g-SGF; that is, crystallization in the composites starts first on the surface of the microfillers and then spreads out into the polymer matrix. This might explain the extremely fast rate of crystallization kinetics observed in the composites. 1 2 3 4 5 1 2 3 4 5