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Research Papers

Study on the Cure Kinetic Behavior of Thermosetting Polyurethane Solids and Foams: Effect of Temperature, Density, and Carbon Nanofiber

[+] Author and Article Information
Mrinal C. Saha1

School of Aerospace and Mechanical Engineering, University of Oklahoma, Norman, OK 73019msaha@ou.edu

Bipul Barua, Sriram Mohan

School of Aerospace and Mechanical Engineering, University of Oklahoma, Norman, OK 73019

1

Corresponding author.

J. Eng. Mater. Technol 133(1), 011015 (Dec 03, 2010) (6 pages) doi:10.1115/1.4002649 History: Received March 08, 2010; Revised August 30, 2010; Published December 03, 2010; Online December 03, 2010

Cure kinetic behavior was studied for both thermosetting polyurethane (PU) solids and foams. The effects of cure temperature, foam density, and carbon nanofiber (CNF) contents were examined. Cure studies were performed experimentally by measuring the evolution of complex shear modulus as a function of time using an advanced polymer analyzer operating in dynamic shear mode. Isothermal cure behavior of PU solid and foams was investigated at four different temperatures, namely, 25°C, 45°C, 60°C, and 80°C and at three different amounts of CNF, namely, 0.01%, 0.05%, and 0.1% by weight. The cure data were analyzed by using an autocatalytic cure kinetic model. The cure behavior of both solid and foam was found to be temperature dependent. Addition of CNF was also found to affect the cure behavior of the PU foam. It was observed that the PU foam with 0.1% CNF shows the highest polymerization reaction compared with the neat foam. It was also observed that the reaction rate constants follow an Arrhenius dependence on temperature, whereas the reaction orders remain fairly constant. A simple predictive model using the reaction orders indicated that the maximum cure reaction rate was occurred at 37.5% conversion.

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Figures

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Figure 1

Extraction of cure parameters showing (a) sigmoidal curve fitting of experimental data and (b) best fitting of the autocatalytic cure model

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Figure 2

Evolution of shear modulus of PU solid as a function of cure time for different isothermal cure conditions

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Figure 3

Comparison of degree of cure, α(=G∗/G∗max) of PU foam AT415 at different temperatures

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Figure 4

Comparison of degree of cure for PU solid and PU foams with different densities

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Figure 5

Variation of complex shear modulus of PU404 foam as a function of time for different CNFs

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Figure 6

(a) SEM micrographs showing the cell size distribution due to the addition of CNF; (b) SEM micrographs showing the CNF presence on the surface of the cell edges

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Figure 7

Arrhenius temperature dependency of rate constants for PU AT415 foam

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