Thermal Degradation studies of nitroplasticized estane 5703 utilizing [sup 13] C enriched model polymers.

Conference · Tue Jan 01 00:00:00 EST 2002

OSTI ID:976235

Wrobleski, Debra A; Langlois, D A ^[1]; Orler, E B ^[2]; Schoonover, J R ^[3]; Osborn, J C ^[4]; Small, J H ^[5]

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1. David A.
2. E. Bruce
3. Jon R.
4. Jill C.
5. James H.

Predicting the lifetime of PBX 9501 is critical to assurance of the reliability of the nuclear weapons stockpile. Ln support of the Lifetime Prediction Model, we have been investigating the physical and chemical aging processes that can potentially affect the lifetime of PBX 9501. Surveillance data of stockpile PBX 9501 binder have shown a decrease in Estane molecular weight as a fiinction of age. Estane is a poly(ester urethane) consisting of poly(buly1ene adipate) as the flexible soft segment and 4,4{prime}-methylenediphenyl-1,1{prime}-diisocyanate (MDI) chain extended with 1,4-butanediol (BDO) as the rigid hard segment efforts have focused on chemical reactions that may cause chain scission of Estane through hydrolytic degradation of the polyester soft segments. Thermal aging of Estane in the absence of water shows no signs of hydrolytic degradation, whereas, appearance of high molecular weight species has been observed for Estane aged at elevated temperatures in the presence of nitroplasticizer. These high molecular weight species are most likely due to branching reactions that eventually leads to formation of an insoluble, cross-linked gel. While the mechanisms of hydrolytic degradation of polyesters has been addressed, the degradations reactions of poly(ester urethane) (PESU) in the presence of NP are not well understood. We have prepared a series of isotopically enriched PESU model compounds chemically similar to Estane for aging experiments in order to understand possible cross-linking mechanisms. Changes in physical properties are observed with less than 1% chemical cross-linking. Isotopic enrichment of 13C from 1.1 % natural abundance to 100% improves the sensitivity of spectroscopic techniques so that small quantities of degradation products can be observed. Because degradation reaction mechanisms of importance may occur at the hard segment portion of the polymer, we have prepared 13C PESU with 13C labeled at the methylene carbon. These model polymers have been foi-mulated into a polymer-rich binder without stabilizer, thennally aged under different enviroimients, and examined using NMR and FTIR spectroscopy to identify degradation products and possible degradation pathways. Results of these preliminary aging studies on unstabilized polymer rich binder are presented herein.

• Research Organization: Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
• Sponsoring Organization: USDOE
• OSTI ID: 976235
• Report Number(s): LA-UR-02-4593; TRN: US201009%%619
• Resource Relation: Conference: Submitted to: High Explosives Aging Conference, Monterey, CA, July 22-26, 2002
• Country of Publication: United States
• Language: English

Related Subjects

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEFENSE
99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE
ABUNDANCE
AGING
BINDERS
CARBON
CHEMICAL EXPLOSIVES
CHEMICAL REACTIONS
CROSS-LINKING
LIFETIME
MOLECULAR WEIGHT
NUCLEAR WEAPONS
PHYSICAL PROPERTIES
POLYESTERS
POLYMERS
REACTION KINETICS
RELIABILITY
SENSITIVITY
SPECTROSCOPY
STOCKPILES
THERMAL DEGRADATION
URETHANE