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The relationship between polymer network parameters and speed of viscoelastic (VE) recovery was studied for viscoelastic polyurethane foams. Reactive network simulation method was developed which use relative reactivity parameters derived from literature and from experiment. Relative reactivity of butylene oxide (BO) based secondary hydroxyl groups were estimated by comparing simulation results with...
A library of 20 bio-based succinate (SA) diol, co-diol, and co-diacid polyester polyols (PESPs) was generated and characterized, giving detailed understanding for tuning of their thermal transitions and rheological parameters. SA and 1,3-propanediol, 1,4-butanediol (BDO), 1,6-hexanediol, 2,2-dimethyl-1,3-propanediol, 3-methyl-1,5-pentanediol, diethylene glycol (DEG), adipic acid, or sebacic acid,...
Crystallization kinetics, thermodynamics, and powder XRD measurements were performed on polyester polyols (PESP) made from succinic acid, SA, or adipic acid, AA, with 1,4-butanediol, BDO, or 1,6-hexanediol, HDO, at 2000 Da Mn. The SA BDO PESP exhibited the greatest crystallization supercooling. The Avrami crystallization kinetics n values are 4 or higher, indicative of sporadic nucleation of spherulitic...
In this study, the distributions of hard segment lengths in flexible and viscoelastic polyurethane foams are investigated. To that extent, MALDI spectra of hard segment chains from polyurethane (“PU”) viscoelastic (“Visco”) and conventional flexible (“Flex”) foam series were obtained and analyzed. Results indicate that within each foam series, there was no significant difference at different water...
Correlations between polyurethane foam formulation and foam aging are shown to simplify when sufficient data are available to eliminate casual relationships. The numerous factors that are purported to result in faster or slower foam aging are shown to primarily reflect how those factors influence polyurethane hard segment structure. Specifically, changes in formulation that results in better phase...
A model is presented in which compression set of TDI foams is a result of thermal and stress-induced relative flow of the hard and soft phase following hydrogen bond disruption. The majority of the soft segment consists of a mobile phase that exhibits liquid-like dynamics. However, a significant fraction of the soft segment is immobilized due to hydrogen bond interactions with the phase-separated...
Semi-crystalline polyester diols with relatively high melting points and enthalpies of crystallization are shown to form nearly co-continuous lamellar structures in thermoplastic polyurethanes using polyether soft segments. This high aspect ratio crystalline structure results in materials with exceptional tensile and elastic properties compared to materials made with conventional semi-crystalline...
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