Thermal and Mechanical Behavior of Unsaturated Polyesters Filled with Phase Change Material Go ¨khan C ¸ aylı, Selim Ku ¨ sefog ˘lu Department of Chemistry and Polymer Research Center, Bogazici University, Istanbul, Turkey Received 2 October 2004; accepted 25 June 2005 DOI 10.1002/app.23181 Published online in Wiley InterScience (www.interscience.wiley.com). ABSTRACT: Samples of commercial unsaturated polyes- ter (UPE) resin, filled with phase-changeable fillers (PCMs), were prepared, and the thermal and mechanical properties of the cured samples were examined. Fillers chosen were paraffin and Wood’s metal. Samples were prepared by mak- ing dispersions of these fillers in liquid unsaturated polyes- ter followed by curing with methyl ethyl ketone peroxide (MEKP) and conaphtanate and rigid thermoset samples filled with PCM particles were obtained. The thermal and mechanical behaviors of such a filled composite around the melting points of fillers are very interesting. Effects of vary- ing proportions of PCM on mechanical and thermal prop- erties of final products were examined. The samples show thermal melting behavior without undergoing a change in physical state. Decreases in the maximum working temper- ature from 75 to 53°C for metal-filled samples and from 75 to 43°C for paraffin-filled samples were observed by using dynamic mechanical thermal analysis. Differential scanning calorimetry indicated that heat absorption of paraffin sam- ples were higher than that of metal-filled samples. For par- affin-filled samples, heats of fusion were 3.44 cal/g for 10% filled sample and 6.35 cal/g for 20% filled sample. For Wood’s metal-filled samples, heats of fusion were 1.18 cal/g for 10% metal-filled sample and 1.54 cal/g for 20% metal- filled sample. Surface hardness was tested with Shormeter D. Surface hardness of metal-filled composites varied from 86 to 34 shore D at 21°C and 80.6 to 35 shore D at 80°C. For paraffin-filled samples, surface hardness changed from 86 to 42 shore D at 21°C and from 80.6 to 13 shore D. Morphology of the samples was determined by scanning electron micros- copy, of the crack surfaces. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 832– 838, 2006 Key words: unsaturated polyesters; phase change materials; fillers; thermal properties; mechanical properties INTRODUCTION Unsaturated polyesters, also called polyester resins, are based on macromolecules with a polyester back- bone in which both a saturated acid, such as phthalic or isophthalic, and an unsaturated acid, such as maleic or fumaric acid, are condensed with a dihydric alco- hols. The degree of crosslinking can be controlled through the concentration of unsaturated acids. 1 The length of crosslinks can be controlled to some degree by concentration and type of crosslinking reactive di- luents employed. Rigidity can be introduced by the use of aromatic acids or glycols, and a high degree of crosslinking. Unsaturated polyesters are one of the most widely used liquid molding resins in the world. Many inert solids are added to polyesters to improve mechanical properties and decrease cost. These materials, called fillers or reinforcers, are inert and infusible inorganic materials such as calcite, alumina, clays, mica, or fi- berglass. 2 Composites manufactured in this manner are important in automotive, boat, infrastructure, and sporting goods industries. In this work, we introduce the concept of meltable i.e., phase-changeable fillers. When a substance is used to store and release latent-heat reversibly in a phase transition, they are called “phase change materials” (PCMs). 3–7 PCMs have found some application as heat storage media where their high-heat of fusion is used. Application of PCMs in solar heating, 8 emergency heating, heat-transfer fluids, 9 –11 and cooling fluids for metal grinding, 12 food storage, etc are well known. When such materials are used in a finely divided form as filler in a high-melting plastic, new materials with interesting properties are produced. If the filler is load bearing, such materials should show abrupt and re- versible changes in modulus around the melting point of filler. This property could allow the production of intelligent plastics. When the filler melts, the corre- sponding heat of fusion is absorbed at the melting point of the filler. Reversing this process allows this heat to be emitted by the sample. This property would allow the production of plastic parts that show melt- ing behavior in a thermal sense (i.e., heat absorption) without exhibiting melting behavior externally. To ex- amine the feasibility of such PCM-filled plastics, we Correspondence to: S. H. Ku ¨ sefog ˘ lu (kusef@boun.edu.tr). Contract grant sponsor: DPT Research Fund; contract grant number: 03K120250. Journal of Applied Polymer Science, Vol. 100, 832– 838 (2006) © 2006 Wiley Periodicals, Inc.