Cryogenic Treatment of Polymer/MWCNT Nano-Composites for Mechanical and Tribological Applications

Cryogenic Treatment of Polymer/MWCNT Nano-Composites for Mechanical and Tribological Applications

Swamini Chopra (Visvesvaraya National Institute of Technology, India), S. Sreya (Visvesvaraya National Institute of Technology, India), Rohit V. Babhulkar (Visvesvaraya National Institute of Technology, India), Swaksha P. Halde (Visvesvaraya National Institute of Technology, India), Kavita A. Deshmukh (Visvesvaraya National Institute of Technology, India) and D. R. Peshwe (Visvesvaraya National Institute of Technology, India)
Copyright: © 2019 |Pages: 59
DOI: 10.4018/978-1-5225-7921-2.ch004

Abstract

The cryogenic treatment of material has been known to motivate structural stability by rearranging its crystallographic structure in metals and by promoting intermolecular as well as intramolecular rearrangements in polymers. Additionally, in case of polymers reinforced with micro fillers, the structural changes brought about by cryogenic treatment are still largely governed by the polymer matrix itself. Thus, when investigated for their mechanical and tribological properties, the response of polymer/MWCNT nano-composites after cryogenic treatment was found to be depending on the cryo-structural modifications in the polymer matrix, followed by the MWCNT interaction to some extent. The enhancement in the mechanical properties of the polymer/MWCNT nano-composites is attributed to the increasing % crystallinity, changes in crystal structure, conversion of less stable phases into more stable phases, change in the nature of bonding and strengthening of interphase between polymer and MWCNT. Thus, for the cryogenic treatment temperature of -185 °C, the optimum soaking period for PA and PA/MWCNT nano-composite was 24 hrs, whereas for PBT and PBT/MWCNT nano-composite it was 12 hrs and 16 hrs, respectively. This agrees well with the popular claim that each polymer has a specific functional group and/or structural characteristic that readily responds to the cryogenic treatments conditions (irrespective of the filler type, content and/or interaction), thereby, modifying the structure and giving superior properties, which makes cryogenic treatment a material specific process.
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Introduction

On a global scenario; the material sector has witnessed momentous growth of polymers as a potential alternative for conventional metals and alloys. The major advantages of using polymers are good mechanical strength coupled with low stiffness-to-weight ratio, ease of manufacturing and excellent reproducibility. Due to the ease of tailoring the polymer properties; they are used in enormous and expanding range of products from paper clips to spaceships. The degree of crystallinity and the extent of rigidity of a polymer can also be controlled during its processing itself or by the incorporation of different types of additives such as fillers, plasticizers, stabilizers, etc. This blending and compounding technology has opened many alternatives to pursue tailoring of any polymer, thus, making a variety of choices available. As the worldwide market grows continuously; the current global production of plastics is approx. 322 million metric tonne per year (Federation of Indian Chambers of Commerce and Industry [FICCI], 2017). Such huge production propose the need of improving quality of polymers and extending their field of application, as even a small enhancement in property seems to be very important economically.

According to FICCI (2017), India is a growing market for plastics and consumes about 16 million tonne annually against a global consumption of 322 million tonne per year. The polymer consumption of India is growing at an average rate of 10% and is expected to touch 30 million tonnes by 2025. It is estimated that current low levels of per capita polymer consumption in India, as compared to developed countries, along with the increased growth in the end use industries offers a huge opportunity for the growth of polymers over long term (FICCI, 2017).

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