Probing the interface behaviour of injection molded thermoplastics by micro-thermal analysis and temperature-modulated differential scanning calorimetry S.A. Edwards, M. Provatas, M. Ginic-Markovic, N.Roy Choudhury * Ian Wark Research Institute, University of South Australia, Mawson Lakes BLVD., SA 5095, Australia Received 26 September 2002; received in revised form 3 March 2003; accepted 2 April 2003 Abstract Micro-thermal analysis (mTAe) and temperature-modulated differential scanning calorimetry (TMDSC) are emerging as powerful instruments for identifying the existence and quantities of phases in multi-component systems, as well as interfacial properties. In this study, these two complimentary techniques are utilised to probe the interphase behaviour of a polycarbonate/acrylonitrile – styrene – acrylate (PC/ASA) blend as they develop during injection molding. Micro-thermal analysis revealed that parts manufactured at high injection time, pack pressure and melt temperature show a densely packed bulk morphology, a significant amount of particle agglomeration as well as the formation of styrene – acrylonitrile/PC (SAN/PC) interphases. TMDSC qualitatively and quantitatively characterized the PC/ASA’s multi- phase morphology and its interfacial properties both before and after injection molding, indicating a greater amount of PC entering the interphase than SAN. q 2003 Elsevier Science Ltd. All rights reserved. Keywords: Interfaces; Micro-thermal analysis; TMDSC 1. Introduction Modern thermoplastic materials are usually blends or composites of complex morphologies that determine their intrinsic properties. The performance of any complex material is mainly controlled by its component suprastruc- ture design and properties or morphology. Polymer morphology thus deals with the arrangement of polymer molecules into amorphous or crystalline regions, the form and structure of these regions and the manner in which they are organised into more complex units. Morphology of a multi-component system or blend defines the spatial arrangement of the component phases [1]. Modern thermal analysis techniques such as micro- thermal analysis and temperature-modulated differential scanning calorimetry (TMDSC) are emerging as powerful tools for identifying the existence and quantities of phases in multi-component systems [2–4], as well as the properties of interfaces between phases [1,5–7]. Micro-thermal analysis is a unique tool that combines the capabilities of advanced thermal analysis with atomic force microscopy (AFM) [8–14], closely examining the surface and near-surface layers of substrates, correlating physical properties and topography with observed phases and boundary layers [15]. Furthermore, by applying a heating signal on a small area of the solid substrate, it is possible to perform localised thermal analysis (LTA) in highly focused areas of interest on the sample to obtain data such as glass transition ðT g Þ; crystallization and melting temperatures [16]. Although various microscopic methods [1] have been used to characterize the morphology of acrylonitrile– butadiene –styrene (ABS) and PC/ABS blends, the appli- cation of micro-thermal analysis to the characterization of interphases developed while processing blends such as polycarbonate/acrylonitrile – styrene – acrylate (PC/ASA) has not yet been reported. The current state of knowledge of this instrument is in its early stages and thus few references are available outlining the principle and modes of its operation. To date, most studies conducted using micro- thermal analysis have been applied in the realm of pharmaceutical chemistry [17] and biological sciences [18–20]. In our previous work [6] we reported the use of micro-thermal analysis in characterising the in situ devel- oped multi-phase morphology of engineered surface defects on ideal and non-ideal PC/ASA parts. When such a rubber- modified polymer melt cools and solidifies, it forms a gradient in molecular packing and hence density. In general, 0032-3861/03/$ - see front matter q 2003 Elsevier Science Ltd. All rights reserved. doi:10.1016/S0032-3861(03)00291-X Polymer 44 (2003) 3661–3670 www.elsevier.com/locate/polymer * Corresponding author. Tel.: þ 61-8-8302-3719; fax: þ61-8-8302-3755. E-mail address: namita.choudhury@unisa.edu.au (N.R. Choudhury).