Study On The Polyether Elastomer And Its Performances In Composite Solid Propellant

Composite solid propellant is usually composed of the high molecular weight binder and solid fillers consisted of solid oxidants and single-compound explosive,and the excellent mechanical properties are essential for its application perfornance.The improvement of the mechanical properties of the propellant at wide temperature ranges?-50⁷0°C?is a research hotspot.As the carrier of the solid fillers,the chemical structure of the binder and its cross-linked network are the decisive factors of the mechanical properties of the solid propellant.Therefore,the research of the chemical structure of the polyether and the property adjustment of the polyether cross-linked network are of great importance for the improvement of the mechanical properties of composite propellant.?1?For the ethylene oxide-tetrahydrofuran random copolyether P?E-co-T?,the sequence structure of the P?E-co-T?with different molecular weights including terminal units,copolymer composition,and the sequence distribution of THF units in P?E-co-T?chains was investigated by the quantitative ¹³C-NMR spectra.The existence of the micro-block[THF]_n?n?3?has been confirmed in the P?E-co-T?chains,and the content of the micro-block[THF]_n in P?E-co-T?chains with different molecular weights were calculated.The crystallization behavior of the P?E-co-T?with different molecular weights were studied by the wide angle X-ray diffraction?WAXD?and DSC,and the results revealed that the molecular weight dependence of the crystallization behavior of the P?E-co-T?was closely related to the content of the micro-block[THF]_n in P?E-co-T?chains.The polyether polyurethane elastomers were prepared by using the P?E-co-T?as binder and isocyanate N100 as curing agent.The relationship between the network structure,crystallization behavior,and mechanical properties were investigated.Because of the existence of the side reactions during the curing process,the cross-linked networkws of the polyether polyurethane elastomers were irregular and unperfect,which in turn gives rise to a linear change of the mechanical properties of the elastomers at room temperature?20°C?and high temperature?60°C?with the curing parameter R.Meanwhile,at low temperature?-40°C?,the different crystallization behavior caused by the cross-linked network induced a totally opposite mechanical properties of the elastomers changing linearly with R values.?2?The propargyl-terminated polyether PTPET with different molecular weights were synthesized by using the hydroxyl-terminated polyether P?E-co-T?as raw materials,and the structure of the polyether PTPET was confirmed by the FT-IR and¹³C-NMR spectra.Based on the click chemistry reaction,the polytriazole polyether elastomers were prepared by using the polyether PTPET as binder pre-polymer and polyazide compound GAP as a curing agent.The relationship between cross-linked network,crystallization behavior and mechanical properties of the elastomers has been investigated.Compared with the polyether polyurethane elastomers,because of the absence of side reaction in click chemistry reaction,the polyether polytriazole elastomers exhibited a totally different cross-linked network,and the cross-linked network structural parameters showed a parabola shapes with increasing curing parameter R.The mechanical properties of the polyether polytriazole elastomers at room temperature?20°C?and high temperature?60°C?were determined by the network structure,while the mechanical properties at low temperature?-40°C?were dominated by the crystallization behavior.Compared with the polyether polyurethane elastomers,because of the absence of side reaction in click chemistry reaction,the polyether polytriazole elastomers have more regular network structure.Therefore,for the same R value,the polytriazole elastomer exhibited much higher tensile stress and modulus.Meanwhile,the crystallization of the polytriazole elastomer was restricted by the regular network structure.Therefore,at low temperature?-40°C?the tensile stress of the polyether polytriazole elastomer is smaller than that of the polyether polyurethane elastomer.?3?The small azide terminated compound KL-170 and azide terminated polyether APTET with high molecular weight were employed as chain extender to improve the mechanical properties of the polyether polytriazole elastomer.The reluctant polytriazole elastomer exhibited much higher elongation at break.The chain extender ATPET increased the elongation at break and slightly decreased the tensile stress of the reluctant polytriazole elastomer.The chain extender KL-170 increased the elongation at break and remained the tensile stress of the reluctant polytriazole elastomer.?4?Based on the click chemistry reaction,the bonding agents TNG-OH containing hydroxyl group and azide group,and the bonding agents TNG-NH₂containing amino group and azide group were synthesized by using 1,4-butynediol,propargylamine and small multi-azide compound.The structure of TNG-OH and TNG-NH₂ were confirmed by the FT-IR and ¹³C-NMR spectrum.The thermal stability of the bonding agents TNG-OH and TNG-NH₂ were analyzed by TG,and the results revealed that the TNG-OH and TNG-NH₂ exhibited excellent thermal stability,and the initial degradation temperatures of the TNG-OH and TNG-NH₂ are about200°C.The bonding agents TNG-OH and TNG-NH₂ were applied in the polyether polytriazole AP/RDX/Al solid composite propellant.The results revealed that the mechanical properties of the polyether polytriazole propellants were dramatically improved by the addition of TNG-OH and TNG-NH₂,while the mechanical properties of the polyether polytriazole solid properties containing the hyantoin bonding agent LBA-604 showed few signs of improvement.