Single-phase polyurethane properties

Elastic Modulus, Network Structure, and Ultimate Tensile Properties of Single-Phase Polyurethane Elastomers... 

Studies have been made of the elastic (time-independent) properties of single-phase polyurethane elastomers, including those prepared from a diisocyanate, a triol, and a diol, such as dihydroxy-terminated poly (propylene oxide) (1,2), and also from dihydroxy-terminated polymers and a triisocyanate (3,4,5). In this paper, equilibrium stress-strain data for three polyurethane elastomers, carefully prepared and studied some years ago (6), are presented along with their shear moduli. For two of these elastomers, primarily, consideration is given to the contributions to the modulus of elastically active chains and topological interactions between such chains. Toward this end, the concentration of active chains, vc, is calculated from the sol fraction and the initial formulation which consisted of a diisocyanate, a triol, a dihydroxy-terminated polyether, and a small amount of monohydroxy polyether. As all active junctions are trifunctional, their concentration always... 

Also, single-phase polyurethane PUE-TL was synthesized for comparison of sorption properties of this material and nano-heterogeneous SPUU. PUE-TL was synthesized on the base of prepolymer of OTM cured by mixture of the initial OTM and ohgopropyl-ene oxide triolLaprol 373 (M = 370 g mol ). 

Property Styrenic Copolyester COPE Polyurethane TPU Polymide TPA TPO EA Two Phase EA Single Phase lonomer... 

Earlier work on chain extended HPLs has shown that these derivatives produce uniform (i.e., single phase) polymers with Tg varying in accordance with the Gordon-Taylor relationship (12). Polyurethanes from chain-extended HPLs were found to be rubber-like at room temperature with modulus declining as lignin content is reduced (8). Star-like structure determines functionality, Tg, viscosity, and several other properties that influence utility as polymer segment. 

There is another group of polyurethanes that is chemically crosslinked with a crosslinker, either triol or polyamine or polyisocyanate. They are single-phase elastomers, and they display lower strengths than the thermoplastic urethanes. However, their properties are less temperature sensitive, and elastic recovery is generally considerably better (permanent set is smaller) than in TPUs. Their strength can be improved by adding proper fillers. Such systems are called cast systems since they are processed by casting... 

The successful utilization of Reaction Injection Molding (RIM) to fabricate complex polyurethane shapes In a single step from relatively low viscosity streams has led to a search for other chemical systems which can be fabricated by the RIM process. The rapid polymerization of molten caprolactam by anionic catalysis has been utilized to develop attractive nylon RIM systems. The incorporation of a rubber segment In the polymer chain allows the fabrication of high Impact or even elastomeric nylon parts. The combination of a rubber phase with the high melting (215°C) crystalline nylon phase provides useful properties at low temperatures as well as at elevated temperatures. 

Even a single polymer can have a composite structure. Here, the phase geometry and mechanical properties are considered for polymers that separate into two amorphous phases. Block copolymers usually have sufficient block lengths to allow micron-scale phase separation. Later on, we have considered smaller scale microstructures caused by the spinodal decomposition of polyurethanes. Semi-crystalline polymers will be considered in Section 4.6. 

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