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2006 Progress Report: Plant-Derived Materials to Enhance the Performance of Polyurethane Materials
EPA Grant Number: R831436Title: Plant-Derived Materials to Enhance the Performance of Polyurethane Materials
Investigators: Nelson, Chad , Hsu, Shaw Ling
Institution: University of Massachusetts - Amherst
EPA Project Officer: Richards, April
Project Period: January 5, 2004 through January 4, 2007
Project Period Covered by this Report: January 5, 2005 through January 4, 2006
Project Amount: $350,000
RFA: Technology for a Sustainable Environment (2003)
Research Category: Pollution Prevention/Sustainable Development
Description:
Objective:This project aims to increase the physical properties of polyurethane foams, coatings, and adhesive by adding plant-derived materials, and thereby reduce the need for excess isocyanate usage. The statistics are staggering. Currently, at least 2 billion pounds (2000 statistics) of isocyanates are being used in the U.S. production of polyurethanes. In the state of Massachusetts alone, the amount of isocyanate used is shocking. The usage of toluene diisocyanates (TDIs) increased by 42 percent between 1990 and 1998. Such large consumption of isocyanates is directly related to the large number of products that are useful. The health hazards of working with and using isocyanates are numerous and severe. Isocyanates, possible carcinogens, are severe irritants to the skin, eyes, respiratory system, gastrointestinal tract, and central nervous system, with several long-term effects such as asthma attacks, possible memory loss, or even genetic changes. The dangers to people working with formulations containing isocyanates are known and extreme precautions are usually taken. The public is exposed to isocyanates because residual amounts of unreacted TDI or methylene bis-phenylisocyanate often are found in polyurethane products. The public also may be exposed directly to isocyanates with various polyurethane products. Given that > 2 billion pounds of isocyanates are used annually in the United States, a reduction in isocyanate usage must be a serious national concern.
Generally speaking, isocyanate usage is approximately 680 times more than stoichiometrically necessary in commercial formulations. This is because the chemical compositions cannot be controlled easily due to uncertain miscibility behavior. The central focus of this research program is to reduce isocyanate usage by improving product properties through addition of biomass feedstocks. These improvements, in most applications, correspond to better mechanical performance of polyurethanes by replacing some of the crucial structural elements with nontoxic reinforcements. We aim for foams of higher modulus, lower hysteresis, higher elongation, and better performance at elevated humidity. The environmental concerns can only be reduced by achieving better fundamental understanding of the parameters governing the processing of polyurethanes. This understanding can only be achieved by having better science. The technology that we develop for the foam industry can be easily transferred to adhesive and coating industries, second only to foam manufacturers in isocyanate usage. Our approach to this end is in the idea of using reinforcement to improve the overall mechanical properties.
Progress Summary:This project deals with two aspects of high performance materials involving the use of biomass feedstocks. In one case, we have developed polyurethane formulations with significant reduction of the most toxic component, isocyanate. In the other part, in conjunction with our industrial partners, we are developing new applications for biomass-based poly(lactic acid).
Miscibility is known to be a critical issue to be addressed in controlling polyurethane reactions. Immiscible formulations lead to reaction mechanisms that are difficult to analyze. In a one-shot foam process, these components must be physically mixed in order for chemical reaction to occur. When this happens, urea hard segments first form through the polymerization of diisocyanates and water. This “blowing reaction” generates carbon dioxide. The hydroxyl end group of a soft segment then reacts with an isocyanate of a hard block and creates a urethane linkage to form the final polymer structure. The influence of these soft segments on physical properties of polyurethanes may be much more significant than just being the elastomeric connecting elements of the dispersed hard segment domains. Our studies suggest that the miscibility of water with the reactant polyol may play a crucial role. It is generally not recognized that poly(ethylene oxide) in water has a theta temperature at 32°C, transforming a water-miscible polymer to one that does not readily mix with water. For reactive blends such as polyurethane formulations, significant changes in miscibility may result from a relatively small rise in temperature. In fact, we have established that the temperature rise in foam formulations is significantly higher than would be needed for such a miscibility change. It is thus crucial to understand the factors that govern the stability of polyurethane blends involving plant-based polyols. Only then is it possible to stabilize the formulation that contains water, even at concentrations as low as 2-3 percent.
During this program, we have carried out numerous studies illustrating how small changes in chemical structure, end groups, and molecular weight can all significantly influence the miscibility behavior of polyurethane formulations. We have developed experimental techniques (scattering and spectroscopy) to characterize phase boundaries and molecular origins of specific interactions of various components. In addition, we have developed various simulation techniques to predict the overall phase behavior utilizing the experimental interaction parameters. The correlation between physical properties (e.g., elongation and tear strengths), molecular structure (functionality and molecular weight), and miscibility behavior have been investigated. For example, the prepolymers involving a polyester, polycaprolactone (PCL), which has a different chemical structure and narrower molecular distribution (pdi = 1.4) than other polyesters, can exhibit a different phase diagram.
The phase behavior of the polypropylene glycol (PPG)/PCL/Acrylic ternary system was found to be quite similar to the PPG/poly(hexamethylene adipate)/Acrylic copolymer system. All three binary subsystems are partially miscible, producing a one-phase region in the ternary blends. The ratio of methylene to ester groups for poly(hexamethylene adipate) (PHMA) and poly(hexamethylene sebacate) (PHMS) and PCL repeat units are 5, 7, and 5, respectively, suggesting that the dipole density of the aliphatic polyester influenced the miscibility with the polyether. In contrast, this change in structure does not affect the miscibility with the acrylic component. The sensitivity of miscibility to the chemical structure of the polyester selected for formulation of polyurethane adhesives is illustrated.
Because biomass feedstocks do not enjoy the tremendous investment in research as has been provided for petroleum feedstocks, considerably more research is needed to characterize these plant-derived polymers. Once these polymers are characterized, their incorporation into polyurethane formulations can be investigated. Poly(lactic acid) had not been used because of the high structural perfection and the high degree of crystallinity induced during processing. We have characterized the inherent structural rigidity and correlated the changes in chain conformation. We have identified the intermolecular forces that stabilized the crystalline units. In addition, we have been able to control the crystallization process by addition of configurational defects. For example, the addition of D-isomer to the all L segments can improve the aging behavior of the polymer. The origin of the extraordinary stability of the stereocomplex of the D and L chains also has been understood.
Future Activities:We will continue to develop various simulation techniques to predict the overall phase behavior utilizing the experimental interaction parameters. The correlation between physical properties (e.g., elongation and tear strengths), molecular structure (functionality and molecular weight), and miscibility behavior will be investigated. We also will continue to investigate additional polyurethane formulations that incorporate greater fractions of renewable feedstocks.
Journal Articles on this Report: 13 Displayed | Download in RIS Format
| Other project views: | All 13 publications | 13 publications in selected types | All 13 journal articles |
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Aou K, Kang S, Hsu SL. Morphological study on thermal shrinkage and dimensional stability associated with oriented poly(lactic acid). Macromolecules 2005;38(18):7730-7735. |
R831436 (2006) |
not available |
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Aou K, Hsu SL. Trichroic vibrational analysis on the α-form of poly(lactic acid) crystals using highly oriented fibers and spherulites. Macromolecules 2006;39(9):3337-3344. |
R831436 (2006) |
not available |
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Duffy DJ, Heintz AM, Stidham HD, Hsu SL, Suen W, Paul CW. The competitive influence of specific interactions and extent of reaction on the miscibility of ternary reactive polymer blends: model for polyurethane adhesives. International Journal of Adhesion & Adhesives 2005;25(1):39-46. |
R831436 (2006) |
not available |
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Hashida T, Jeong YG, Hua Y, Hsu SL, Paul CW. Spectroscopic study on morphology evolution in polymer blends. Macromolecules 2005;38(7):2876-2882. |
R831436 (2006) |
not available |
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Heintz AM, Duffy DJ, Nelson CM, Hua Y, Hsu SL, Suen W, Paul CW. A spectroscopic analysis of the phase evolution in polyurethane foams. Macromolecules 2005;38(22):9192-9199. |
R831436 (2006) |
not available |
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Jeong YG, Hashida T, Hsu SL, Paul CW. Factors influencing curing behavior in phase-separated structures. Macromolecules 2005;38(7):2889-2896. |
R831436 (2006) |
not available |
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Jeong YG, Hashida T, Wu G, Hsu SL, Paul CW. Analysis of the multistep solidification process in polymer blends. Macromolecules 2006;39(1):274-280. |
R831436 (2006) |
not available |
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Jeong YG, Pagodina NV, Jiang C, Hsu SL, Paul CW. Effects of polyester-poor phase microstructures on viscosity development of polymer blends. Macromolecules 2006;39(14):4907-4913. |
R831436 (2006) |
not available |
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Jeong YG, Ramalingam S, Archer J, Hsu SL, Paul CW. Influence of copolymer configuration on the phase behavior of ternary blends. Journal of Physical Chemistry B 2006;110(6):2541-2548. |
R831436 (2006) |
not available |
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Jeong YG, Hashida T, Nelson CM, Hsu SL, Paul CW. Morphology evolution and associated curing kinetics in reactive blends. International Journal of Adhesion & Adhesives 2006;26(8):600-608. |
R831436 (2006) |
not available |
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Pogodina NV, Jeong YG, Ramalingam S, Jiang C, Hsu SL, Paul CW. Crystallization-induced interconnected structure in semicrystallizable polyester/polyether binary blends. Macromolecules 2006;39(19):6672-6676. |
R831436 (2006) |
not available |
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Ren Z, Zeng X, Yang X, Ma D, Hsu SL. Molecular modeling of the H-bonds in polyurethane with multiple donors and acceptors. Polymer 2005;46(26):12337-12347. |
R831436 (2006) |
not available |
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Yang X, Kang S, Yang Y, Aou K, Hsu SL. Raman spectroscopic study of conformational changes in the amorphous phase of poly(lactic acid) during deformation. Polymer 2004;45(12):4241-4248. |
R831436 (2006) |
not available |
green chemistry,
,
INTERNATIONAL COOPERATION, TREATMENT/CONTROL, Sustainable Industry/Business, Scientific Discipline, RFA, Technology for Sustainable Environment, Sustainable Environment, Chemical Engineering, Technology, Chemicals Management, Environmental Chemistry, Ecology and Ecosystems, clean technologies, green design, elastomers, green chemistry, plant derived polyurethane, coatings, alternative materials, carcinogenicity
Relevant Websites:
Progress and Final Reports:
Original Abstract