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Many structure/property relationships of hydrolyzed poly(ester urethane) (PEU) – a thermoplastic – have been reported. Examples include changes in molecular weight vs. elongation at break and crosslink density vs. mechanical strength. However, the effect of molecular weight (or molar mass) reduction on some physical, thermal, and chemical properties of hydrolyzed PEU have not been reported. Therefore, a large set of hydrolyzed PEU (Estane®5703) samples were obtained from two aging experiments: 1) accelerated aging conducted under various environments (air, nitrogen, moisture) and at 64 °C and below for almost three years, and 2) natural aging conducted under ambient conditions for moremore » than three decades. The hydrolyzed samples were characterized via multi-detection gel permeation chromatography (GPC), thermogravimetric analysis (TGA), modulated differential scanning calorimetry (mDSC), UV–vis spectroscopy, nuclear magnetic resonance (NMR), and Fourier-transform infrared (FTIR) spectroscopy techniques. Hydrolysis of ester linkages in the soft-segments decreases both the molecular weight (M_w) and the melting point (T_m) of Estane (from ~55 °C to 39 °C). Aging above this T_m, increased mobility of polymer chains and water diffusivity in the PEU matrix alter the PEU degradation pathway from those expected at aging temperatures below this T_m and have significant bearing on the critical molecular weight (M_C) at which the physical, chemical, thermal, and mechanical properties of Estane change abruptly. While a M_C value of 20 kDa is found for PEU hydrolysis at mild temperatures (e.g., as low as 39 °C), the value of M_C increases with increasing aging temperatures. To complement the existing structure/property relationships reported in the literature, more correlations are obtained, which include the effect of M_w on polydispersity, intrinsic viscosity (Mark-Houwink equation), UV extinction coefficient, and dn/dc (GPC analysis) values. Furthermore, we seek to bolster previously reported aging models for PEU by developing a practical model with which the extent of degradation and material performance can be predicted based on aging under different temperature ranges both above and below the melting point of Estane.« less

The effect of water concentration on the aging behavior of blend components in plastic bonded explosive (PBX) 9501 is investigated when samples were aged up to 24 months under various conditions. Additionally, the blend components studied here are: poly(urethane ester) (Estane®5703) (Estane), nitroplasticizer (NP), and antioxidant Irganox 1010 (Irg1010). The experimental results reveal that NP is prone to thermally degrading and producing H₂O, NO_x, and HNO_x species, which are the predominant species to consume Irg1010 during PBX 9501 aging under inert environment. As Irg1010 is completely consumed, Estane degrades through oxidation and NP addition, in addition to well anticipated hydrolysis.more » The competition among hydrolysis, oxidation, and NP addition results in non-monotonical changes in the molecular weight of Estane over the aging process.« less