Chain‐extended, hydroxyterminated‐polybutadiene‐based polyurethaneureas: Synthesis, reaction kinetics, and properties

Abstract

Hydroxyterminated-polybutadiene-based prepolyurethanes were prepared with two different catalysts, dibutyltindilaurate (DBTDL) and triethylamine (TEA); chain extension of the prepolyurethanes followed with two different aromatic diamines, oxydianiline and 4,4Ј-diaminodiphenylsulfone, in various concentrations. The prepolyurethane synthesis followed second-order kinetics, with the DBTDL catalyst showing better efficiency for urethane formation than TEA. TEA-catalyzed synthesis suffered from the self-association of isocyanates as a major side reaction, following second-order kinetics with respect to isocyanate concentration. Although there was a gradual increase in the intrinsic viscosity during prepolyurethane synthesis in the presence of DBTDL, the intrinsic viscosity remained almost constant with the progress of the reaction in the presence of TEA. The tensile properties of prepolyurethane and polyurethaneureas synthesized in DBTDL-catalyzed reactions were higher than the properties of those synthesized in TEA-catalyzed reactions. The variation of the tensile strength with the diamine concentration was correlated with the crosslink density and sol fraction. The solubility of the hard segment of polyurethaneurea in the reaction medium appeared to be important in influencing the tensile properties. The effects of the diamine concentration (chain extender) on the diffusion coefficient and activation energy of diffusion of toluene in polyurethaneureas were studied.

Chemical reaction of maritime pine sapwood (Pinus pinaster Soland) with alkoxysilane molecules: A study of chemical pathways

“…Though it has never been used with wood, DBTDL was reported to catalyse the reaction of isocyanates with alcohols (Subrayan et al 2000;Gupta and Adhikari 2001;Ni et al 2002) and was recently applied to the synthesis of cellulose carbamates, in mild conditions (Mormann and Michel 2002). Results in Table 1 show that a significant WPG can be obtained without a catalyst, but the reaction rate was improved up to three times when Py or DBTDL were added.…”

Diffusion behavior of hexane in diamine chain‐extended hydroxyterminated polybutadiene based polyurethanes

“…and P ϭ P 0 exp ϪEp/RT (7) where, E D is the activation energy required to create opening between the polymer chains to permit penetrant molecules to pass. E D is the function of inter-and intrachain forces.…”

“…The reaction was run for 45 min at 30°C to obtain a viscous liquid. A thin sheet of prepolyurethane was cast from the viscous liquid on a clean plane glass plate and left overnight for moisture curing followed by heating at 80°C for 7 h. 7 Polyurethaneureas, PUUSD 20, PUUSD 50, and PUUSD 100 were prepared by adding 20, 50, and 100-mol % DADPS (with respect to HTPB), respectively, after 40 min of the start of prepolyurethane synthesis. Polyurethaneurea sheet was cast and cured in the same way as done for prepolyurethane.…”

Aqueous polyurethane dispersions derived from polycarbonatediols

“…Polyurethanes have been found in wide applications such as coatings and adhesives1 due to their unique properties, and great efforts have been made in chemistry and physics 2–10. In the polyurethane system, aqueous polyurethane dispersions are expanding their applications in coatings, adhesives, paper sizings, etc., due to the trend of environmental regulations to decrease the level of solvent emissions 11–13.…”