Use of Recycled Polystyrene with Polyurethane in Polymer Network Compositions Andre ´ Leonardo Leite, 1 Juliana Kloss, 1 Eduardo Marques Trindade, 2 Ronilson Vasconcelos Barbosa, 1 Anto ˆ nio Reinaldo Cestari, 3 Eunice Fragoso, 3 So ˆ nia Faria Zawadzki 1 1 Departamento de Quı ´mica, Universidade Federal do Parana ´, Curitba, Parana ´, Brazil 2 Instituto de Tecnologia para o Desenvolvimento, LACTEC, Curitiba, Parana ´, Brazil 3 Universidade Federal do Sergipe, Sergipe, Brazil Received 2 March 2006; accepted 20 April 2006 DOI 10.1002/app.25710 Published online in Wiley InterScience (www.interscience.wiley.com). ABSTRACT: Postconsumer polymer recycling is a tech- nology that involves many fields of science. The production of plastics has increased in recent years, and the products have many applications. Because of this, waste plastics are also increasing, causing many environmental problems due to the slow rate of natural decomposition of synthetic poly- mers. Polymer chemistry and process engineering are good tools for decreasing the problems caused by inappropriate polymer disposal. The subject of this work was the prepara- tion of polymer networks based on recycled polystyrene (in the crystal form, PS; or in the expanded form, EPS) and poly- urethane. The compositions were prepared by reaction between the polyurethanes (PU) components in the presence of recycled PS or EPS dissolved in the styrene monomer con- taining benzoyl peroxide as a free radical initiator. 1,4-buta- nediol (BDO) was used as chain extender for PU network. The compositions were characterized by the evaluation of mechanical properties, thermogravimetric analysis, and morphological analysis. The PS or EPS concentration used in the mixtures was in the 1–5 wt % range. The addition of PS or EPS changed the mechanical behavior as well as the final morphology of the compositions. The use of the PS/PU or EPS/PU network systems is a way of decreasing PS or EPS discards decreasing this environmental problem. Ó 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2714–2719, 2007 Key words: polystyrene; polyurethanes; interpenetranting networks; mechanical properties; morphology INTRODUCTION Polyurethanes (PU) can be applied in many technolog- ical sectors. The correct choice of the PU compounds leads to the perfect combination between hard and soft segments. This fact and the possibility of obtain- ing different crosslinking degrees play an important rule in the resulting properties and final applications of the polymer. PU synthesis is based on the reaction between isocyanate and hydroxyl groups resulting in the characteristic urethanic link. The crosslinking structure is obtained using a trifunctional alcohol, for instance. The reaction is shown in Figure 1. 1–4 PU is considered as a segmented copolymer. The flexible segment is constituted by a terminated hydroxyl group polymer (f ‡ 2,0) called polyol. In gen- eral the polyol has a lower glass transiton temperature (T g ) that imposes an elastomeric characteristic on PU. The rigid segments contain polar urethane links typi- cally with higher T g . 4,5 PU are used to produce foams (rigid or flexible) but can be also used to make elastomeric polymers, inks, fibers, textiles, and adhesives. 4–6 On the other hand, polystyrene (PS) is broadly used in the industry and it can be used in many forms, mainly in crystal or in expanded forms (EPS) among others. Irregular PS waste has been causing serious problems for the environment and re-use has been identified as an economical and interesting alternative for solving this problem. 7 In some situations it is interesting to have new properties to allow a specific use of a material. Thus it was observed that polymer combination constituted an important way of reaching this particular applica- tion. The combination of two or more different poly- meric matrices is an alternative for producing new compositions with specific and better properties, which are not available from any of the mixture com- ponents. Most of the combinations are obtained by the use of two polymers producing the so-called binary mixtures. The final properties depend on the com- ponents, but also on the way in which the mixture is produced. 4 Among the various combination methods involving polymers we can call attention to: mechanical mix- tures or blends; chemical compositions (they are Correspondence to: S. F. Zawadzki (zawadzki@quimica. ufpr.br). Journal of Applied Polymer Science, Vol. 104, 2714–2719 (2007) V V C 2007 Wiley Periodicals, Inc.