Isothermal crystallization kinetics of fly ash filled iso-polypropylene composite- and a new physical approach Dilip Chandra Deb Nath Æ Sri Bandyopadhyay Æ Aibing Yu Æ Darryl Blackburn Æ Chris White Æ Susy Varughese Received: 2 February 2009 / Accepted: 30 July 2009 / Published online: 29 August 2009 Ó Akade ´miai Kiado ´, Budapest, Hungary 2009 Abstract Composites of pre-mixed fly ash (FA) and isotactic-polypropylene (PP) with varying degree of FA, 0, 20, 45 and 60 wt% were prepared by injection moulding at 483 K. The isothermal crystallization kinetics of the neat PP and composites are calculated using exotherms obtained from differential scanning calorimetry (DSC) at different isothermal crystallization temperatures (T c ) 403, 405 and 407 K. The lowest points of the exotherm peaks were shifted to higher crystallization times in the ranges of 0.75–1.50 min with the increasing of T c in neat PP and composites regardless of FA percentage addition. The values of Avrami exponent n are found as non-integral number ranges 2 \ n \ 4, and the calculated initial crystal thickness values of PP change slightly with increasing super cooling temperature as well as FA content. Keywords Polypropylene  Fly ash  Composites  Isothermal crystallization  DSC Introduction PP based composites have a wide ranges of applications in many engineering and industrial atmosphere. At higher temperatures, semicrystalline polymers in polymer-filler composites show different thermal and mechanical proper- ties. The degree of crystallinity and crystalline morphology depend on the type, size and shape of filler present in the polymer composite. The semicrystalline PP generally forms three different crystallographic phases, viz., a-monoclinic phase, ß-pseudohexagonal phase and c-orthorhombic phase. The pseudohexagonal ß-crystalline phase melts at lower temperature, and more stable monoclinic a phase melts at higher temperature [1, 2]. The mechanical properties of PP can dramatically be improved by the addition of inorganic natural clay as reinforcement filler [3–8]. The selection of filler composed of PP is a critical task in designing and controlling the mechanical and thermal properties of composite. The mechanism of enhanced mechanical properties of PP composites is strongly related to the suppression, acceler- ation and/or formation of new crystalline structures of PP chains in the presence of filler. The filler in general influ- ences the crystallization of a, ß and c forms and dimen- sional distribution of spherulites of PP in composites. The investigation of crystallization kinetics on filler nucleating function, therefore, will give direct evidence of alteration of crystalline phase of PP in composites. The crystalliza- tion kinetics can be studied under thermally stable and/or dynamic non-isothermal condition [9]. The potential nucleating fillers reported for crystalliza- tion of PP chains in PP-filler composites are glass fibre [10], calcium carbonate [11, 12], talc [13], carbon black [14], clay [15], kaolin [16], ZnO [17], carbon nanotube [18] and silica oxide [19, 20]. A number of studies have reported the utilization of industrial by-product FA as filler value added material in polymer composites, e.g., epoxy [21], polyester [22] and PP [23–26]. The tensile strength of the composite materials decreased with the addition of FA. D. C. D. Nath  S. Bandyopadhyay (&)  A. Yu School of Material Science and Engineering, The University of New South Wales, Sydney, NSW 2052, Australia e-mail: S.Bandyopadhyay@unsw.edu.au D. Blackburn  C. White Research and Ash Development, Cement Australia, Brisbane, QLD, Australia S. Varughese Department of Chemical Engineering, IIT Madras, Chennai 600 036, India 123 J Therm Anal Calorim (2010) 99:423–429 DOI 10.1007/s10973-009-0408-6