Real-Time Morphological Observation of Isotactic Polypropylene and Poly(ethylene-co-octene) Rubber Blend during Temperature Change Michio Ono, 1,2 * Ken Nakajima, 2 Mayumi Misawa, 3 Toshio Nishi 2 1 SunAllomer Ltd., Kawasaki Development Center, Kawasaki-Ku, Kawasaki, Kanagawa 210-0863, Japan 2 Department of Organic and Polymeric Materials, Faculty of Engineering, Tokyo Institute of Technology, Meguro-Ku, Tokyo 152-8552, Japan 3 Nihon Veeco K. K., Application Group Metrology, Chuou-Ku, Tokyo104-0045 Japan Received 23 August 2007; accepted 20 November 2007 DOI 10.1002/app.27803 Published online 29 January 2008 in Wiley InterScience (www.interscience.wiley.com). ABSTRACT: In the injection- and compression-molded specimens composed of isotactic polypropylene (iPP) and poly(ethylene-co-octene) rubber (EOR) blend, its morpho- logical changes with temperature variation were investi- gated using an atomic force microscopy equipped with a heater accessory. Phase-separated sea-island structures com- prising the iPP matrix (sea) and the EOR domains (island) were clearly observed in both specimens. In the injection- molded specimen, the morphology of the EOR domains was fibrous along flow direction (FD). In the iPP matrix, a stripe- like structure consisting of alternating iPP crystalline lamel- lae and amorphous region was clearly observed at room temperature. As increasing temperatures, the iPP amor- phous regions seemed to shrink gradually and could not be identified at 808C. By contrast, in the compression-molded specimen, the EOR domains were circular in shape, and the alternate structure comprising the iPP crystal lamellae and amorphous regions was also found. At elevated tempera- tures, the iPP amorphous regions gradually enlarged. The analysis of the apparent activation energy obtained by a dynamic mechanical thermal analysis revealed that the dif- ferences in the morphological behavior in the iPP matrix region between the both specimens were attributed to the differences in the mobility in the iPP crystal regions. Ó 2008 Wiley Periodicals, Inc. J Appl Polym Sci 108: 1857–1864, 2008 Key words: polypropylene (PP); atomic force microscopy (AFM); injection molding INTRODUCTION Isotactic polypropylene (iPP) is outstanding among other polymers because of its price/mechanical properties balance, easy processability, and good wetherability. 1 Hence, it has been in wide use of many fields such as automobile, consumer products, sheets and textile processed by injection, blow, extru- sion, and spinning. The iPP has been usually used in the form of polymer alloy by being melt-blended with various thermoplastic elastomers (TPEs) to improve brittle impact properties. 2–6 In particular, the iPP/TPE alloys have been widely applied to injection-molded parts in automobile indus- try. These parts are usually subjected to be quite severe thermal conditions ranging from less than 2308C for the exterior parts to more than  808C for the interior ones. It is known that such a temperature change has a great influence on some properties, impact strength, 2,4,6 Young’s modulus, 7 and linear thermal expansion coef- ficient. 8–11 The mechanism of the change in the physi- cal properties toward temperature change has not been fully understood. This is mainly because of lack of the information about the real-time morphological change toward temperature variation. In this study, using an atomic force microscopy (AFM), we investigated the morphological changes with temperature variation for the specimens com- posed of iPP and poly(ethylene-co-octene) rubber (EOR) blend fabricated by two different molding meth- ods, injection- and compression molding. It was found that the interlamella morphologies in the iPP matrix changed quite differently between the injection and the compression specimen at elevated temperatures. EXPERIMENTAL Raw material and specimen preparation Isotactic polypropylene (iPP) used in this study, which was kindly supplied by SunAllomer, had 5600 Pa s of a zero shear viscosity (h m * ) at 2108C, *Present address: Dow Japan Development Center, Dow Chemical Japan Ltd., 8-1, Ukishima-Cho, Kawasaki-Ku, Kawasaki-Shi, Kanagawa-Ken, 210-0862, Japan. Correspondence to: M. Ono (mono@dow.com) Journal of Applied Polymer Science, Vol. 108, 1857–1864 (2008) V VC 2008 Wiley Periodicals, Inc.