Study On The Mechanical Properties Of 3,3-diazidomethyloxetane-tetrahydrofuran Copolyether Elastomer

Polymer binder is the carrier of the composite solid propellant’s mechanical properties.Azide polyether binder has become popular in some special application,thanks to its high energy and greenness.The elaborate research of the mechanical properties of azide polyether binder is important for the improvement of the mechanical properties of composite propellant.Usinghydroxylterminated3,3-diazidomethyloxetane（BAMO）,tetrahydrofuran（THF）equal molar ratio quasi-ideal random copolyether of poly（3,3-diazidomethyloxetane-co-tetrahydrofuran）（PBT）as a prepolymer,the influence factors just like preparation temperature,temperature,stretching rate and plasticizer of property of PBT elastomer were researched.The end-crosslinked PBT elastomer was prepared by a carbmate reaction with the quasi-ideal random copolyether of PBT.The results revealed that the tensile modulus of PBT elastomer decreases with increasing strains at the temperatures above room temperature.The analysis of the aggregation evolution of PBT elastomer demonstrated that crystallization of BAMO micro-blocks existing in PBT strands was inducted at strain of 320%at-40℃because of the strand orientation in strain direction and decreasing configuration entropy,which has enforced the interaction among strands and therefore the mechanical properties of PBT elastomer was enhanced.In Chapter 3,it was researched that the effect of preparation temperature on the mechanical properties of PBT elastomer.The experiments showed that low-temperature curing PBT elastomer contains crystallization of micro-blocks under static condition.Its fusion temperature is about 33℃and it is an irreversible behavior.Because of the crystallization behavior,the low-temperature curing PBT elastomer has batter mechanical properties than high-temperature curing PBT at 20℃.In addition,these two elastomers are able to get strain-induced crystallization at-40℃.So they have high stresses and stains.In Chapter 4,The effect of curing parameter R and strain rates were researched.The equilibrium swelling method showed that the apparent average molecular weights（M_c）decreases and the apparent densities of elastomer strands（N₀）increases with R increasing from 0.8 to 1.3.At 20℃and 60℃,the stresses of PBT elastomers increase with increasing R.The strains generally decrease.The stresses and strains of PBT elastomers gradually increase with increasing strain rates at 20℃.The stresses of PBT elastomers increase and the strains decrease with increasing strain rates at-40℃.It is worth mentioning that the elastomers with higher N₀or under higher strain rate are easy to get strain-induced crystallization at low temperature.At last,the changing of the mechanical properties of PBT elastomer is studied with adding plasticizer A3.The adding of A3 makes the strains decrease sharply at 60℃and stay the same at 20℃.The elastomer with plasticizer needs higher strains to get strain-induced crystallization at-40℃.