Journal of Polymer and Biopolymer Physics Chemistry, 2014, Vol. 2, No. 1, 25-28 Available online at http://pubs.sciepub.com/jpbpc/2/1/4 © Science and Education Publishing DOI:10.12691/jpbpc-2-1-4 Variations in Specific Heat and Microstructure in Natural Rubber Filled with Different Fillers as Studied by Differential Scanning Calorimetry Arunava Mandal 1 , Sandip Pan 1 , Subrata Mukherjee 1 , Achintya K. Saha 1 , Sabu Thomas 2 , Asmita Sengupta 1,* 1 Physics Department, Visva-Bharati Central University, P.O.- Santiniketan, West Bengal, India 2 Centre for Nanoscience and Nanotechnology, Mahatma Gandhi University, Kottayam, Kerala, India *Corresponding author: asmita_sengupta@hotmail.com Received December 24, 2013; Revised March 18, 2014; Accepted March 20, 2014 Abstract The variation of specific heat (C p ) of natural rubber (NR) is studied by Differential Scanning Calorimetry (DSC). The NR samples are filled with different fillers (nanoclay, TiO 2 , and nanosilica) at different concentrations. The DSC measurements are done in N 2 atmosphere with constant pressure of 0.3 bar to prevent any oxidation of the samples. The temperature has been varied up to 210°C from -40°C at a constant heating rate of 10°C \min throughout the experiment and Proteus analysis software is used to study the variation of specific heat (C p ) as function of both temperature and filler concentrations. The investigation shows that the Cp values increase with the increase of filler concentrations. Due to nanometer range diameter, these fillers fill up some of the free volume holes of NR sample. The fillers also make cross-link with NR chains causing an increase the molecular weight of NR as well as the C p values. Thus the fillers act as active fillers for NR sample. Keywords: differential scanning calorimetry, natural rubber, fillers, specific heat, free volume Cite This Article: Arunava Mandal, Sandip Pan, Subrata Mukherjee, Achintya K. Saha, Sabu Thomas, Asmita Sengupta, and Asmita Sengupta, “Variations in Specific Heat and Microstructure in Natural Rubber Filled with Different Fillers as Studied by Differential Scanning Calorimetry.” Journal of Polymer and Biopolymer Physics Chemistry, vol. 2, no. 1 (2014): 25-28. doi: 10.12691/jpbpc-2-1-4. 1. Introduction In recent years in polymer research, a key problem is to relate the atomic scale free volume to the thermal and mechanical properties of polymer [1]. These free volumes appear, in the amorphous region of the polymers due to their structural disorder, in form of many irregularly shaped cavities or holes of atomic and molecular dimension. The presence of free volume decreases the density of the polymer and effect remarkably on the mechanical and thermal properties. Free volume is affected by irradiation of ion beams, aging and by addition of various fillers [2-7]. Raw natural rubber (NR) undergoes curing process for it to be useful for any practical and industrial purpose. It is therefore compounded by mixing with varity of materials such as sulfur, zinc oxide, stearic acid etc. and then cure in a process called vulcanization [8]. During this process, NR forms cross links with sulfur improving its quality and usefulness [9]. Rubber is a class of polymeric materials, which is expected to show rubber elasticity when in use. Natural rubber is in use for its versatility as an elastomeric material. Polymeric materials such as natural rubber (NR), containing filler particles of nanometer size have excellent physical, mechanical, and thermal properties compared to their conventional micro composite counterparts [10,11,12]. The main aim of the addition of fillers into natural rubber is to improve the properties and to cheapen the material for use in material science and industry. Among many types of filler carbon black is the most important filler due to its high ability to improve the quality of NR. But it has a serious drawback. It originates from petroleum and makes the NR black due to pollution. Several groups have studied NR and its blend compounds with different methods such as viscosity measurements, differential scanning calorimetry, dynamic mechanical spectroscopy, positron annihilation spectroscopy etc. [5,13,14,15,16,17]. The microstructure of free volume of NR filled with TiO 2 , Nanosilica(NS), Nanoclay(NC) have been studied by positron annihilation spectroscopy [5]. In this paper an attempt is made to study microstructure and thermal properties NR filled with TiO 2 , NS, NC at different concentrations by Differential Scanning Calorimetry (DSC). DSC measures the change in thermal properties and microstructures of any sample as a function of temperature. The heat capacity of a substance can be defined as the amount of heat required to change its temperature by unity. A more useful quantity is the specific heat capacity, which is the heat capacity per unit molecular weight of the substance. The heat capacity of a polymer can be classified into two categories: one is for the “solid” state of the polymer, may be denoted as C ps and the other one is for the “liquid” state of the polymer, may be denoted as