Study On Preparation Of Azido-terminated Ethylene Oxide-Tetrahydrofuran Copolymer And Properties Of Polyether Polytriazole Elastomers

The adhesives can combine the different components of the propellant together, so the properties of the propellant will be directly determined by the performance of the adhesives. The advantages of energetic adhesive of azido-terminal polymers are high energy, high heat release and not releasing oxygen in decomposition,so it has great development prospects.Polyurethane adhesive can be obtained by the curing of polyol(such as polyether) and isocyanate,due to the reaction can produce carbon dioxide with water,resulting in crosslinked network structure not complete. The click-chemistry reaction, a typical reaction is alkynyl groups and azide compounds, is simple,not sensitive to water,high selectivity and high yield. The elastomers by the reaction possess better mechanical property.(1) In this paper, the hydroxyl-terminated ethylene oxide-tetrahydrofuran copolymer(PET) was a reaction substrate, the cloro-terminated ethylene oxide-tetrahydrofuran copolymer(ClPET) was prepared through the reaction between PET and thionyl chloride,then azido-terminated ethylene oxide-tetrahydrofuran copolymer(ATPET) was synthesized from ClPET and sodium azide,and found a suitable synthetic condition by changning reaction conditions of chlorination reaction and azide reaction conditions, such as the concentration, molar ratio, reaction temperature, reaction time. FTIR and NMR analysis indicated that hydroxyl-terminated groups had been completely replaced of azido-terminated groups; GPC tests showed the molecular weight and molecular weight distribution was almost unchanged and no side reactions,such as chain scission, occured in the synthesis. EA results indicated that the measured azide value of the product was very close to the theoretical one. These results showed that the target product was obtained. Viscosity tests showed PET and ATPET are pseudoplastic fluid and PET possesses high viscosity compared ATPET due to the hydrogen bonds. The ATPET was sealed and tested by NMR spectra and Element analysis every month, test results showed that ATPET was very stable and hadn’t any form of decomposition.(2) Utilizing stong alkali NaH, tetrakis(2-propynyloxymethyl)methane(TPOM) had been synthesized through the etherifiction between pentaerythritol and propargyl bromide. FTIR and 13C-NMR spectra results showed that hydroxyl peak disappeared completely in objective product TPOM, meanwhile alkynyl group emerged. HPLC-MS analysis showed that TPOM purity was 97.14%. XRD test indicated TPOM was a crystal structure. Thermogravimetric analysis showed that the initial decomposition temperature of TPOM was 168 oC, and the thermal decomposition was a three-stage pyrolysis process.(3) With substances containing multifunctional alkynyl molecules as curing agents, R value and functionality on click chemistry elastomers of ATPET were studied. Propargylamine(f = 3) as the curing agent, different R value polymer triazole elastomers were prepared. The results showed that tensile strength and elastic modulus of elastomer first increased and then decreased with increasing R-value, elongation at break first decreased and then increased with increasing R-value. The mechanical properties of the polytriazole elastomers showed a parabolic dependence on the R value,which achieved the most value at R=1.0. Swelling experiments showed the network structure had a minimum apparent molecular weight and a maximum apparent density when R=1.0. DMA test showed the elastomer exhibited the lowest dissipation factor tanδ at the stoichiometric ratio.TG suggested that the weight-loss process was one-step decomposition, and the elastomer decomposed from polyether strands, not triazole groups. Tetrakis-(2-propynyloxymethyl) methane(f = 4) as the curing agent, ATPET as adhesive, different R value polymer triazole elastomers were prepared. The mechanical properties of the polytriazole elastomers revealed that elongation at break obtained minimum and tensile strength and elastic modulus highest when R = 1.1. Swelling experiments showed that the network structure was the most complete when R = 1.1.