Model Identification of a Twin Screw Extruder for Thermoplastic Vulcanizate (TPV) Applications M. Trifkovic, 1 M. Sheikhzadeh, 2 K. Choo, 3 S. Rohani 1 1 Department of Chemical and Biochemical Engineering, The University of Western Ontario, London, Ontario, N6A 5B9, Canada 2 Lanxess Corporation, C/O 1457 London Road, Sarnia, Ontario, N7S 6K4, Canada 3 Lambton College, 1457 London Road, Sarnia, Ontario, N7S 6K4, Canada Multi-input multi-output (MIMO) models of a twin- screw co-rotating extruder for thermoplastic vulcani- zate (TPV) are developed using the process identifica- tion techniques. The process inputs are screw speed (SS) and barrel temperature (WT). The three outputs are motor load (ML), melt temperature (MT), and melt pressure (MP). Two appropriate rubbers for TPV appli- cations with different physical and mechanical proper- ties are used for the experimentation. The process model is obtained from the experimental input–output data using various identification techniques such as least squares and prediction error. Recursive online model identification is performed on the process to update the model parameters in real time. To perform the identification studies, the process data was trans- ferred via OPC server from the local PLC (Program- mable Logic Controller) to the Advanced Control and Identification toolbox in MATLAB software. The effect of rubber properties and two curative agents (Peroxide and Phenolic) in the TPV experiment are studied on the final identified models. This comprehensive model identification study provided sufficient accurate mod- els for further model based process analysis and con- trol for TPV applications. POLYM. ENG. SCI., 50:1168–1177, 2010. ª 2009 Society of Plastics Engineers INTRODUCTION The concept of physically/chemically combining two or more polymers via blending to obtain new polymeric materials with the desired properties has received much attention from the point of view of fundamental and practical interests [1]. Blends of polypropylene with rub- bers are widely found in industry. Depending on the ratio between components, these blends may be used either as high-impact materials when the rubber content in the blend is low or as thermoplastic elastomers (TPEs) when the rubber content is high [2]. Thermoplastic elastomer compositions based on the blends of uncured ethylene-propylene-diene monomer (EPDM) rubber and polypropylene (PP) is referred to as thermoplastic polyolefin (TPO), whereas the blends of PP and dynamically vulcanized EPDM rubber are referred to as thermoplastic vulcanizates (TPVs) [3]. Dynamic vul- canization, at which crosslinking of elastomer proceeds simultaneously with its blending with thermoplastic com- ponent leads to changes in the morphological structure of PP-elastomer blends. Both, TPO and TPV are currently being widely used in the automotive industry [3]. One of the most practical ways to produce TPVs is the extrusion process. Since the dynamic vulcanization (a reaction between curing agents and the mixture of plastic and rub- ber) occurs during the mixing process, the manufacturing of TPVs in an extruder is referred to as ‘reactive extru- sion’. These processes involve carrying out chemical reac- tions deliberately in conjunction with a conventional extrusion operation [4]. Although a significant amount of research has been conducted in the field of extrusion process design and optimization, very few attempts have been made to design effective control systems and methodologies that can assure acceptable product end-use performance for this class of processes. The lack of suitable control systems can be mainly attributed to the existence of two major challenges in designing these systems for the reactive extrusion process. First, the product properties are measured at a very low fre- quency, and second, information regarding the effect of underlying process mechanisms such as reaction, heat trans- fer, and melting on product properties is rarely available [4]. Correspondence to: K. Choo; e-mail: kim.choo@lambton.on.ca Contract grant sponsors: Ontario Centers of Excellence (OCE), Ontario Innovation Trust (OIT), Natural Sciences and Engineering Research Council of Canada (NSERC), Lanxess Corporation, and The Lambton College of Applied Arts and Technology. DOI 10.1002/pen.21646 Published online in Wiley InterScience (www.interscience.wiley.com). V V C 2009 Society of Plastics Engineers POLYMER ENGINEERING AND SCIENCE—-2010