Molecular Dynamics Simulation on the Binder of Ethylene Oxide–Tetrahydrofuran Copolyether Cross-Linked with N100

Abstract

Ethylene oxide−tetrahydrofuran copolyether (P(E-co-T)) crosslinked with isocyanate Desmodur (N100) is widely used as the binder system in solid energetic propellant. The effect of its cross-linking degree on the physical properties is important for the evaluation of the propellant binders. In this work, an efficient method was presented for simulating the crosslinking process, predicting the microscopic behaviors and macroperformances of cross-linked P(E-co-T)−N100 binder systems. During the simulation of cross-linking network forming, the initial physical mixture model of P(E-co-T)/N100 was firstly constructed and optimized through molecular dynamics. Then the possible cross-linking topology was generated by means of the identification of the reactive site pairs. In this way, the P(E-co-T)−N100 cross-linking pathway was realized by alternate structure optimization and junction reaction. The cross-linking intermediate models were analyzed, and the density and mechanical property profiles have revealed the increasing tendency with cross-linking progressing, which is corresponding to the experimental results. Moreover, volume−temperature behaviors of P(E-co-T) and cross-linked P(E-co-T)−N100 systems were simulated to study the cold resistance characterized by glass transition temperature. The mean-squared displacements and free volume data have verified that the cross-linking structure of P(E-co-T)−N100 restricts the molecular mobility, which is helpful to explain the higher glass transition temperature and stronger mechanical properties.

Crosslinking mechanisms, structure and glass transition in phthalonitrile resins: Insight from computer multiscale simulations and experiments

“…Shefer and Gottlieb reviewed that the increase in T g may be associated with several effects: reduction of the concentration of chain ends, which is believed to be the most important in the formation of thermosets and end‐linked networks; “plasticizer effect” that is disappearance of small molecular weight molecules; formation of branch points and crosslinks; non‐Gaussian chain statistics, affecting highly crosslinked networks; and the formation of cyclic structures. Recently Lan et al performed MD simulation of crosslinking process of propellant binder and showed that T g mainly depended on the motions of the molecules and freedom space and that the conformational change of highly crosslinked molecules was “frozen out.” Thus, T g of crosslinked network is higher due to corresponding restriction of molecular relaxation.…”

Influences of Bu‐NENA and BDNPA/F Plasticizers on the Properties of Binder for High‐Energy NEPE Propellants

“…The affinity between both PET polyether and N-100 polyisocyanate with plasticizers was evaluated by MD simulation under the COMPASSII force field, by using the Forcite module of Materials Studio 2017 [16]. The detailed process for the model construction is shown in the supplementary document.…”

Network regulation and properties optimization of glycidyl azide polymer‐based materials as a candidate of solid propellant binder via alternating the functionality of propargyl‐terminated polyether

“…33 Because of excellent mutual compatibility with nitrate plasticizers, Poly[THF-co-EO] has been commonly used to prepare polyurethane-type binders in nitrate ester plasticized polyether (NEPE) propellants. 34,35 In this study, the Poly(THF-co-EO)s with two and three functionalities were used as the raw material and terminated with alkyne groups instead of hydroxyl groups to produce propargyl-terminated ethylene oxidetetrahydrofuran copolymer (PPET) with two (p-) and three (t-) alkyne functionalities, respectively. Two network-structured GAPbased binders were fabricated via the azide alkyne Huisgen cycloaddition with the p-PPET and t-PPET.…”

“…Ethylene oxide‐tetrahydrofuran copolymer (Poly(THF‐co‐EO)) is a nontoxic and highly flexible copolyether . Because of excellent mutual compatibility with nitrate plasticizers, Poly[THF‐co‐EO] has been commonly used to prepare polyurethane‐type binders in nitrate ester plasticized polyether (NEPE) propellants . In this study, the Poly(THF‐co‐EO)s with two and three functionalities were used as the raw material and terminated with alkyne groups instead of hydroxyl groups to produce propargyl‐terminated ethylene oxide‐tetrahydrofuran copolymer (PPET) with two ( p‐ ) and three ( t‐ ) alkyne functionalities, respectively.…”