Temporary shape development in shape memory nanocomposites using magnetic force Atefeh Golbang, Mehrdad Kokabi ⇑ Polymer Engineering Department, Faculty of Chemical Engineering, Tarbiat Modares University, P.O. Box 14115-114, Tehran, Islamic Republic of Iran article info Article history: Received 1 December 2010 Received in revised form 5 June 2011 Accepted 13 June 2011 Available online 7 July 2011 Keywords: Shape memory nanocomposites Magnetic field Temporary shape Magnetic particles Crosslinked low density polyethylene abstract Direct mechanical force is used to create a temporary shape in shape memory polymers. This can become difficult in situations where the sample is not directly accessible such as interior in the body. In these cases it is not possible to use a direct mechanical force to deform the sample into temporary shape; therefore other alternative routes should be proposed. The magnetic force is a good candidate for inducing remote deformation. The ability of magnetic field to cause deformation in soft matters has already been revealed. To prove the hypothesis of using magnetic force to create temporary shape, magnetic field active shape memory polymeric nanocomposites were manufactured by incorporation of NdFeB ferromagnetic micro particles in a nanocomposite based on crosslinked low density polyethylene loaded with 2 wt.% of organoclay. The results indicate that as the NdFeB con- tent increases, the reversible temporary deformation induced in the samples by the mag- netic force increases. The effect of NdFeB concentration on the shape recovery progress and the possibility of heat induction in NdFeB filled samples through the application of an alter- nating magnetic field were also examined. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Mechanical force is conventionally used to deform shape memory samples into their temporary shape. Elec- tric [1], magnetic [2] and electromagnetic [3,4] triggering of shape recovery through heat induction in shape memory composites has been performed by scientists over the past years. These methods have replaced the need for direct heating for shape recovery of thermally responsive shape memory polymers. Magnetic stimulation can become very useful especially in the case where the sample is out of ac- cess. Therefore the sample can be heated up through re- mote actuation via magnetic field and the permanent shape can be recovered [5–8]. If it is then required to de- form the sample again to develop another temporary shape while there is still no direct access to the sample, it would be impossible to mechanically deform the sample. In this case, magnetic field actuation could be the answer to this problem. Many researchers have investigated the actuation re- sponse of soft matters to magnetic fields. It has been ob- served that by placing magnetic powder filled hydrogels [9–11] and elastomers [12] in a spatially non-uniform magnetic field, shape changes occur as a result of magnetic forces acting on the magnetic particles. The shape change is due to the strong interaction between magnetic particles and polymer chains, which causes the movement of both magnetic particles and polymer chains as a single unit [13]. The new generation of magnetic elastomers and gels represents a new type of composites, consisting of small (mainly nano- and micron-sized) magnetic particles dis- persed in a high elastic polymeric matrix. These materials are relatively new and exhibit a great number of fascinat- ing phenomena, which are the subject of intensive theoret- ical and experimental researches. The peculiar magneto- elastic properties may be used to create a wide range of motions and to control the shape change and movement. An understanding of magneto-elastic coupling in polymers 0014-3057/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.eurpolymj.2011.06.008 ⇑ Corresponding author. Tel./fax: +98 21 8288 3340. E-mail address: mehrir@modares.ac.ir (M. Kokabi). European Polymer Journal 47 (2011) 1709–1719 Contents lists available at ScienceDirect European Polymer Journal journal homepage: www.elsevier.com/locate/europolj