Equilibrium acid concentrations in hydrolyzed polyesters and polyester–polyurethane elastomers

Abstract

SynopsisEquilibrium acid concentrations, [Ae], were determined in butylene adipate and caprolactone polyesters, of low molecular weight, and in thermoplastic polyurethane elastomers based on these polyesters. Values of [Ae] of the polyesters a t 85°C were 0.7,1.3, and 3-4 X mol/g a t relativehumidities (RH) of 25%,50%, and 93%, respectively.[Ae] of the thermoplastic elastomers a t 85°Cwere about 3 and 7 X lop4 mol/g at 10% and 25% RH, respectively. Values of [Ae] were not very dependent on temperature at constant RH. Equilibrated thermoplastic elastomers had low molecular weights and poor physical properties. Consequently, equilibration does not set a practical limit on hydrolytic degradation, even a t low RH. Equations were developed that described the variation in acid content with time. Rate constants for hydrolysis and esterification increased as RH decreased. Reesterification in the elastomers in the absence of water is too slow to be a useful method of decreasing hydrolytic damage.

Degradation of a poly(ester urethane) elastomer. I. Absorption and diffusion of water in Estane® 5703 and related polymers

“…Brown et al (BLS),7–9 studied a poly(ester urethane) elastomer that was 63% by weight ester, which they denoted as 63 PTMA7 or 63 PBA 8, 9. We use the shorter designation.…”

“…Poly(ester urethanes) are known to degrade by several mechanisms,2, 3 one of which is hydrolysis 4–9. To study the hydrolysis of Estane® 5703 and related poly(ester urethanes), it is necessary to first determine their absorption of water and the diffusion of water through them.…”

“…This is a low fraction of hard segments as compared with many poly(ester urethanes). The polymers used by Schollenberger and coworkers4–6, 14 and Brown et al7–9 had about the same molecular weight PBA but had molar fractions of 0.5 MDI, 0.25 PBA, and 0.25 BDO so that they have a higher hard‐segment fraction than Estane® 5703. Three of the samples used by Potts15 were commercial poly(ester urethanes) that are probably similar to Estane® 5703, but they are not identified in his article.…”

Advances in Solid Propellant Formulations

“…35 ' 36 In principle, both ester and urethane linkages are hydrolyzable in dilute aqueous acid and base solutions, although normally the process is slow. 35 ' 36 In principle, both ester and urethane linkages are hydrolyzable in dilute aqueous acid and base solutions, although normally the process is slow.…”

Degradation of a poly(ester urethane) elastomer. II. Kinetic modeling of the hydrolysis of a poly(butylene adipate)

“…The experiments analyzed in this article are those of Brown, Lowry, and Smith (BLS)2–4 who studied the hydrolytic degradation of several polymers including a poly(ester urethane) that they denoted 63 PTMA [poly(tetramethylene) adipate] and 63 PBA. We use the latter designation for brevity.…”