Paper Number
SG15 

Session
Solids and Glasses

Title
Evidence for deformation dependence of heat capacity in cross-linked natural rubber

Presentation Date and Time
October 9, 2014 (Thursday) 10:50

Track / Room
Track 5 / Commonwealth A1

Authors (Click on name to view author profile)

1. Nieto Simavilla, David (Illinois institute of technology, Chemical and biological engineering)
2. Venerus, David C. (Illinois institute of technology, Chemical and biological engineering)
3. Schieber, Jay D. (Illinois Institute of Yechnology, Chemical and Biological Engineering)

Author and Affiliation Lines (in printed abstract book)
David Nieto Simavilla, David C. Venerus, and Jay D. Schieber
Chemical and biological engineering, Illinois institute of technology, Chicago, IL 60616

Speaker / Presenter 
Nieto Simavilla, David

Text of Abstract
We present a novel Infrared Thermography (IRT) technique to investigate heat capacity dependence on deformation in polymeric materials. This phenomenon is directly related with the longstanding question of whether or not there is an internal energy contribution to rubber elasticity in particular, and to viscoelasticity of polymer liquids in general. By tracking the temperature evolution of stretched samples heated by a laser beam, we are able to measure heat capacity changes with respect to the equilibrium value as a function of elongation. We find that heat capacity increases with stretch ratio in lightly cross-linked cis 1,4- polyisoprene specimens subjected to uniaxial extension. This observed deformation dependence of heat capacity is consistent with an independent set of experiments comparing anisotropy in thermal diffusivity from Forced Rayleigh Scattering and thermal conductivity from steady-state IRT. We evaluate our results with a simple thermodynamic analysis of the internal energy contribution to tension based on classical rubber elasticity results.