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Effect <strong>of</strong> post draw<strong>in</strong>g parameters <strong>of</strong> melt sp<strong>in</strong>n<strong>in</strong>g <strong>of</strong> carbon<br />

nanotube filled polypropylene fiber<br />

Srikanth S. Kamath a *, Arup R. Bhattacharyya a# , Pankaj B. Tambe a , Ajit R. Kulkarni a ,<br />

T.V. Sreekumar b , K<strong>in</strong>gsuk Mukhopadhyay b and Anurag Srivastav b<br />

a Department <strong>of</strong> Metallurgical Eng<strong>in</strong>eer<strong>in</strong>g and Materials Science, Indian Institute <strong>of</strong> Technology<br />

Bombay, Powai, Mumbai- 400076, India<br />

b Defence Materials and Stores Research and Development Establishment (DMSRDE), DRDO,<br />

Kanpur 208013,India<br />

E-mail: arupranjan@iitb.ac.<strong>in</strong><br />

Abstract<br />

Melt spun multiwall carbon nanotubes (MWNT) filled polypropylene (PP) fibers were drawn at draw<br />

ratio <strong>of</strong> 8 with variation <strong>of</strong> post draw<strong>in</strong>g parameters (temperature and speed <strong>of</strong> draw<strong>in</strong>g the composite<br />

fibers) <strong>in</strong> order to understand the effect <strong>of</strong> post draw<strong>in</strong>g parameters on mechanical properties <strong>of</strong><br />

composite fibers. It was found that fiber drawn at high temperature and low draw<strong>in</strong>g speed showed an<br />

<strong>in</strong>crease <strong>in</strong> mechanical properties <strong>of</strong> PP/MWNT composite fibers than any other comb<strong>in</strong>ation <strong>of</strong><br />

variation <strong>of</strong> post draw<strong>in</strong>g parameters.<br />

1. Introduction<br />

Isotactic polypropylene (PP) utilized as a commercial polymeric fiber exhibits a wide range <strong>of</strong><br />

mechanical properties. However, PP fiber needs re<strong>in</strong>forcement <strong>in</strong> order to achieve high stiffness and<br />

strength for eng<strong>in</strong>eer<strong>in</strong>g applications. S<strong>in</strong>ce the discovery <strong>of</strong> carbon nanotubes (CNT) by Iijima [1],<br />

CNT have emerged as a potential candidate as re<strong>in</strong>forc<strong>in</strong>g filler <strong>in</strong> polymer based composite fibers <strong>in</strong><br />

view <strong>of</strong> their unique mechanical, electrical and thermal properties [2]. Fiber with mechanical<br />

properties suitable for advanced eng<strong>in</strong>eer<strong>in</strong>g application require orientation <strong>of</strong> polymer cha<strong>in</strong>s[3-7]<br />

as well as that <strong>of</strong> CNT[8, 9] dur<strong>in</strong>g post draw<strong>in</strong>g operation. It was found that the average orientation<br />

<strong>of</strong> statistical cha<strong>in</strong> segments <strong>of</strong> PP with<strong>in</strong> the sample was <strong>in</strong>dependent <strong>of</strong> the draw<strong>in</strong>g temperature<br />

whereas the yield stress and elongation at break wee strongly <strong>in</strong>fluenced by the applied draw<strong>in</strong>g<br />

temperature. A significant drop <strong>in</strong> yield stress could be observed for a fixed draw ratio with lower<strong>in</strong>g<br />

the draw<strong>in</strong>g temperature. At a certa<strong>in</strong> temperature this drop leads to a transition from brittle to ductile<br />

failure behavior, result<strong>in</strong>g <strong>in</strong> an <strong>in</strong>crease <strong>in</strong> elongation at break [3]. The effect <strong>of</strong> the postdraw<strong>in</strong>g at a<br />

constant draw ratio manifests <strong>in</strong> either high stiffness <strong>in</strong> comb<strong>in</strong>ation with superior draw ability/energy<br />

absorption (lowest possible post draw<strong>in</strong>g temperature, formation <strong>of</strong> mesomorphic phase) or a high<br />

stiffness <strong>in</strong> comb<strong>in</strong>ation with high strength (highest post draw<strong>in</strong>g temperature <strong>in</strong> the aff<strong>in</strong>e<br />

deformation regime) [4].<br />

The aim <strong>of</strong> this work is to understand the effect <strong>of</strong> vary<strong>in</strong>g post draw<strong>in</strong>g parameters (temperature and<br />

speed <strong>of</strong> draw<strong>in</strong>g the composite fibers) at vary<strong>in</strong>g multiwall carbon nanotubes (MWNT)<br />

concentration on the mechanical properties <strong>of</strong> PP/MWNT composite fibers drawn at a fixed draw<br />

ratio <strong>of</strong> 8.

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