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Study on the Coupling Agent and Polyurethane Adhesive in PBX

Author: LiFan
Tutor: YeLin
School: Sichuan University
Course: Materials Science
Keywords: Polymer Bonded Explosive (PBX) TATB Boron-containing coupling agent Adhesive Interface TPU Damping property Mechanical property Micro phase separation
CLC: TQ560.7
Type: Master's thesis
Year: 2007
Downloads: 203
Quote: 3
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Abstract


Polymer Bonded Explosive (PBX) is one of the widely used composite explosive at present, and Triamino-trinitro-benzene (TATB) is a kind of insensitive single-component explosive with high energy, which is applied in PBX commonly. There are very strong intramolecular and intermolecular hydrogen bonds in TATB molecules, resulting in the very low surface energy and poor adhesive performance. Fluoropolymers, which is often applied as bonding materials in TATB-based PBX, have low intermolecular cohesion force, and very low surface tension, which leads to very poor compatibility with other materials. In this work, the synthesis of coupling agents and thermoplastic polyurethane elastomer (TPU) were studied for the interfacial modification of PBX composite, in order to improve the interfacial bonding of explosives and polymers, and enhance the mechanical property of PBX, reduce its sensitivity, and obtain polymer bonding materials with high performance adapting to PBX.Through molecular design, a series of boron-containing coupling agents were synthesized, which were applied to improve the interfacial bonding of fluoropolymer/TATB composite. The boron atom of the coupling agent molecule can form coordinate bond with the fluorine atom of fluoropolymer; and hydrogen atom in its amino group can form hydrogen bond with oxygen atom in nitro-group of TATB. The interfacial performance of the composite was investigated by the measurement of contact angle, surface and interface tension, and adhesive work, and the interfacial bonding mechanism were studied by FTIR, XPS and SEM analysis, and the mechanical property of TATB- based PBX was studied by brazilian test. The results showed that the interfacial tension decreased, the adhesive work increased, and the interfacial bonding was improved remarkably for the composite through being modified by the coupling agents. There was no influence on the chemical stability of TATB when modified with the coupling agents, and the strong hydrogen bond between amino-group of the coupling agents and nitro-group of TATB, and coordination bond between boric atom of the coupling agents and fluorine atom of fluoropolymer were formed. The fluoropolymer/TATB composite modified by CA-4 showed relatively higher mechanical property.Compared with fluoropolymer, TPU has excellent mechanical property, damping property and adhesive property, which play an important role in PBX system as adhesive. A series of polyester-based thermoplastic polyurethanes elastomer(TPU), with different kinds of molecular structure parameter (molecule weight, diisocyanate, hard segment content, soft segment, molecular weight of the soft segment, chain-extending agent), were prepared through bulk synthesis and one-step process. The effects of structure parameter on the mechanic properties and dynamic viscoelasticity of TPU were investigated. The results showed that TPUs using PBA as soft segment and MDI as the diisocyanate had excellent mechanical property, and tensile strength of which reached about 30 MPa. The hardness and the glass transition temperature of polyester-base TPUs were improved and the elongation at break was reduced by increasing mass fraction of hard segment; The tensile strength, hardness and the glass transition temperature of polyester-base TPUs were increased, elongation at break was reduced and the peak temperature of damping factor moved toward low temperature region by increasing the relative molecular mass of soft segment; The tensile strength, hardness were reduced, the elongation at break and the value of damping factor were increased by increasing the length of chain-extending agent, and the damping property was increased by grafting side-chain at the molecule of chain-extending agent. The molecule structure, micro-phase structure, molecule weight and distribution were studied by FTIR, XPS and SEM analysis. The results showed that TPU had high molecule weight with narrow distribution and chemical stability. And there was micro-phase separation in TPU molecule, in which hard segment phase well dispersed in soft segment phase, which can display reinforcing effect on TPU.The synthesized TPU (CMA-14) was used to compound with explosives, and the interfacial tension and adhesive work were studied between explosives and CMA-14 before or after modified by boron-containing coupling agents and titanate coupling agents. The results showed that the interfacial tensions between CMA-14 and explosives were lower than F2314 and explosives, and adhesive works were higher, which indicated better adhesive property, and boron-containing coupling agents and titanate coupling agents can improve the interfacial interaction between TPU and TATB. The mechanical sensitivity of PBX compounded by CMA-14 was tested, and its mechanical property was tested by compression experiment, brazilian test and SEM. The results showed that the impact sensitivity and friction sensitivity of PBX compounded by CMA-14 were decreased, and the compression strength, modulus, breaking strength and compressive strain were all higher than that of F2314. The PBX molding powder was coated by CMA-14 better than F2314, and had smooth surface with litter TATB particles outside.

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CLC: > Industrial Technology > Chemical Industry > Explosives industry, match industry > General issues. > Explosives, pyrotechnics
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