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Title: A kinetic approach to modeling the manufacture of high density strucutral foam: Foaming and polymerization

Abstract

We are studying PMDI polyurethane with a fast catalyst, such that filling and polymerization occur simultaneously. The foam is over-packed to tw ice or more of its free rise density to reach the density of interest. Our approach is to co mbine model development closely with experiments to discover new physics, to parameterize models and to validate the models once they have been developed. The model must be able to repres ent the expansion, filling, curing, and final foam properties. PMDI is chemically blown foam, wh ere carbon dioxide is pr oduced via the reaction of water and isocyanate. The isocyanate also re acts with polyol in a competing reaction, which produces the polymer. A new kinetic model is developed and implemented, which follows a simplified mathematical formalism that decouple s these two reactions. The model predicts the polymerization reaction via condensation chemis try, where vitrification and glass transition temperature evolution must be included to correctly predict this quantity. The foam gas generation kinetics are determined by tracking the molar concentration of both water and carbon dioxide. Understanding the therma l history and loads on the foam due to exothermicity and oven heating is very important to the results, sincemore » the kinetics and ma terial properties are all very sensitive to temperature. The conservation eq uations, including the e quations of motion, an energy balance, and thr ee rate equations are solved via a stabilized finite element method. We assume generalized-Newtonian rheology that is dependent on the cure, gas fraction, and temperature. The conservation equations are comb ined with a level set method to determine the location of the free surface over time. Results from the model are compared to experimental flow visualization data and post-te st CT data for the density. Seve ral geometries are investigated including a mock encapsulation part, two configur ations of a mock stru ctural part, and a bar geometry to specifically test the density model. We have found that the model predicts both average density and filling profiles well. However, it under predicts density gradients, especially in the gravity direction. Thoughts on m odel improvements are also discussed.« less

Authors:
 [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];
  1. Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); Sandia National Laboratories, Livermore, CA (United States)
Publication Date:
Research Org.:
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Sandia National Lab. (SNL-CA), Livermore, CA (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1222534
Report Number(s):
SAND-2015-8282
606314
DOE Contract Number:  
AC04-94AL85000
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English

Citation Formats

Rao, Rekha R., Mondy, Lisa Ann, Noble, David R., Brunini, Victor, Roberts, Christine Cardinal, Long, Kevin Nicholas, Soehnel, Melissa Marie, Celina, Mathias C., Wyatt, Nicholas B., Thompson, Kyle R., and Tinsley, James. A kinetic approach to modeling the manufacture of high density strucutral foam: Foaming and polymerization. United States: N. p., 2015. Web. doi:10.2172/1222534.
Rao, Rekha R., Mondy, Lisa Ann, Noble, David R., Brunini, Victor, Roberts, Christine Cardinal, Long, Kevin Nicholas, Soehnel, Melissa Marie, Celina, Mathias C., Wyatt, Nicholas B., Thompson, Kyle R., & Tinsley, James. A kinetic approach to modeling the manufacture of high density strucutral foam: Foaming and polymerization. United States. https://doi.org/10.2172/1222534
Rao, Rekha R., Mondy, Lisa Ann, Noble, David R., Brunini, Victor, Roberts, Christine Cardinal, Long, Kevin Nicholas, Soehnel, Melissa Marie, Celina, Mathias C., Wyatt, Nicholas B., Thompson, Kyle R., and Tinsley, James. 2015. "A kinetic approach to modeling the manufacture of high density strucutral foam: Foaming and polymerization". United States. https://doi.org/10.2172/1222534. https://www.osti.gov/servlets/purl/1222534.
@article{osti_1222534,
title = {A kinetic approach to modeling the manufacture of high density strucutral foam: Foaming and polymerization},
author = {Rao, Rekha R. and Mondy, Lisa Ann and Noble, David R. and Brunini, Victor and Roberts, Christine Cardinal and Long, Kevin Nicholas and Soehnel, Melissa Marie and Celina, Mathias C. and Wyatt, Nicholas B. and Thompson, Kyle R. and Tinsley, James},
abstractNote = {We are studying PMDI polyurethane with a fast catalyst, such that filling and polymerization occur simultaneously. The foam is over-packed to tw ice or more of its free rise density to reach the density of interest. Our approach is to co mbine model development closely with experiments to discover new physics, to parameterize models and to validate the models once they have been developed. The model must be able to repres ent the expansion, filling, curing, and final foam properties. PMDI is chemically blown foam, wh ere carbon dioxide is pr oduced via the reaction of water and isocyanate. The isocyanate also re acts with polyol in a competing reaction, which produces the polymer. A new kinetic model is developed and implemented, which follows a simplified mathematical formalism that decouple s these two reactions. The model predicts the polymerization reaction via condensation chemis try, where vitrification and glass transition temperature evolution must be included to correctly predict this quantity. The foam gas generation kinetics are determined by tracking the molar concentration of both water and carbon dioxide. Understanding the therma l history and loads on the foam due to exothermicity and oven heating is very important to the results, since the kinetics and ma terial properties are all very sensitive to temperature. The conservation eq uations, including the e quations of motion, an energy balance, and thr ee rate equations are solved via a stabilized finite element method. We assume generalized-Newtonian rheology that is dependent on the cure, gas fraction, and temperature. The conservation equations are comb ined with a level set method to determine the location of the free surface over time. Results from the model are compared to experimental flow visualization data and post-te st CT data for the density. Seve ral geometries are investigated including a mock encapsulation part, two configur ations of a mock stru ctural part, and a bar geometry to specifically test the density model. We have found that the model predicts both average density and filling profiles well. However, it under predicts density gradients, especially in the gravity direction. Thoughts on m odel improvements are also discussed.},
doi = {10.2172/1222534},
url = {https://www.osti.gov/biblio/1222534}, journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue Sep 01 00:00:00 EDT 2015},
month = {Tue Sep 01 00:00:00 EDT 2015}
}