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Volumn 45, Issue 16, 2007, Pages 2123-2135

Theoretical modeling of the relationship between young's modulus and formulation variables for segmented polyurethanes

Author keywords

Computer modeling; Elastomers; Mechanical properties; Modulus; Polyurethanes

Indexed keywords

BLOCK COPOLYMERS; COMPUTER SIMULATION; ELASTIC MODULI; ELASTOMERS; THERMODYNAMIC PROPERTIES;

EID: 34548245534     PISSN: 08876266     EISSN: None     Source Type: Journal    
DOI: 10.1002/polb.21213     Document Type: Article
Times cited : (43)

References (69)
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    • Estimates of cohesive energy density and solubility parameters were performed using program SYNTHIA within Cerius2 package provided by Accelrys, Inc. The program uses the group contribution techniques developed by van Krevelen (ref. 39) and Bicerano ref. 40
    • Estimates of cohesive energy density and solubility parameters were performed using program SYNTHIA within Cerius2 package provided by Accelrys, Inc. The program uses the group contribution techniques developed by van Krevelen (ref. 39) and Bicerano (ref. 40).
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    • Bicerano, J.; Daussin, R. D.; Elwell, M. J. A.; van der Wal, H. R.; Berthevas, P.; Brown, M.; Casati, F.; Farrisey, W.; Fosnaugh, J.; de Genova, R.; Herrington, R.; Hicks, J.; Hinze, K.; Hock, K.; Hunter, D.; Jeng, L.; Laycock, D.; Lidy, W.; Mispreuve, H.; Moore, R.; Nafziger, L.; Norton, M.; Parish, D.; Priester, R.; Skaggs, K.; Stahler, L.; Sweet, F.; Thomas, R.; Turner, R.; Wiltz, G.; Woods, T.; Christenson, C. P.; Schrock, A. K. In Polymeric Foams: Mechanisms and Materials; CRC Press: Boca Raton, 2003; p 173.
    • Bicerano, J.; Daussin, R. D.; Elwell, M. J. A.; van der Wal, H. R.; Berthevas, P.; Brown, M.; Casati, F.; Farrisey, W.; Fosnaugh, J.; de Genova, R.; Herrington, R.; Hicks, J.; Hinze, K.; Hock, K.; Hunter, D.; Jeng, L.; Laycock, D.; Lidy, W.; Mispreuve, H.; Moore, R.; Nafziger, L.; Norton, M.; Parish, D.; Priester, R.; Skaggs, K.; Stahler, L.; Sweet, F.; Thomas, R.; Turner, R.; Wiltz, G.; Woods, T.; Christenson, C. P.; Schrock, A. K. In Polymeric Foams: Mechanisms and Materials; CRC Press: Boca Raton, 2003; p 173.
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    • Percolation exponent 5 typically ranges between 1.5 and 2 (see, e.g., ref. 51), depending on the type of the system and the property described by a percolation model (modulus, conductivity, etc.). There are instances, however, when percolation exponent could be larger than 2 (see, e.g., ref. 52). Various models (e.g., double percolation-see ref. 53) have been proposed to explain these high percolation exponents. In our analysis, we refrain from ascribing any specific meaning to exponent 5 = 2.5 and treat it simply as an adjustable parameter that best describes experimental data.
    • Percolation exponent 5 typically ranges between 1.5 and 2 (see, e.g., ref. 51), depending on the type of the system and the property described by a percolation model (modulus, conductivity, etc.). There are instances, however, when percolation exponent could be larger than 2 (see, e.g., ref. 52). Various models (e.g., double percolation-see ref. 53) have been proposed to explain these high percolation exponents. In our analysis, we refrain from ascribing any specific meaning to exponent 5 = 2.5 and treat it simply as an adjustable parameter that best describes experimental data.
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    • It is important to note that eq 6 should be used only near the vicinity of the hard phase percolation. Indeed, the meaning of the percolation exponent öis to account for the fact that the percolated pathways are not linear but have some complicated morphology; thus, the efficiency of the reinforcement is much less than 100, However, at higher hard segment weight fractions, lamellar domains become thicker and longer, leading to more correlated structures. Ultimately, at very high hard segment weight fractions, the dependence of modulus on the hard segment weight fraction should become closer to linear and then saturate. We are not attempting to describe this region of the phase map in our current paper, concentrating mainly on the composition range more typical for polyurethane elastomers and flexible foams
    • It is important to note that eq 6 should be used only near the vicinity of the hard phase percolation. Indeed, the meaning of the percolation exponent öis to account for the fact that the percolated pathways are not linear but have some complicated morphology; thus, the efficiency of the reinforcement is much less than 100%. However, at higher hard segment weight fractions, lamellar domains become thicker and longer, leading to more correlated structures. Ultimately, at very high hard segment weight fractions, the dependence of modulus on the hard segment weight fraction should become closer to linear and then saturate. We are not attempting to describe this region of the phase map in our current paper, concentrating mainly on the composition range more typical for polyurethane elastomers and flexible foams.
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    • In principle, effective polyol functionality, fp, could itself depend on the composition if one accounts for the hydrogen bonding of the hard segments, not just the covalent bonding. We leave the investigation of this effect for future studies and keep /P a constant, independent of temperature and composition, and determined only by the number of terminal hydroxyl groups per polyol molecule
    • In principle, effective polyol functionality, fp, could itself depend on the composition if one accounts for the hydrogen bonding of the hard segments, not just the covalent bonding. We leave the investigation of this effect for future studies and keep /P a constant, independent of temperature and composition, and determined only by the number of terminal hydroxyl groups per polyol molecule.
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* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.