Preparation And Properties Of Polybutadiene And Polyether Used As Solid Propellants Binders

As an important part of solid propellant,binder can react with the curing agent to form a three-dimensional crosslinked network structure,in which the other groups of solid propellant are entrapped in cross-linking network structure.Therefore,the performance of the binder will directly affect the mechanical properties,low temperature performance and storage performance of solid propellant.Therefore,the preparation and application of new adhesive materials is an important basis for promoting the development of solid propellant.Although the formulation of a new generation of mature propellant requires a long time of accumulation and a lot of scientific research,with the development of polymer science and technology,more and more polymer materials have been developed.Therefore,it is a major scientific research task proposed to adopt advanced polymerization technology to prepare new types of polymer materials and conduct a detailed analysis of their structure and performance to screen out new binder materials that can meet the requirements of advanced solid propellant.This research work has been carried out on the design,synthesis and performance of adhesives for new solid propellants.In the second chapter,hydroxy-terminated polybutadiene(HTPB)with high 1,4-units was prepared by anionic polymerization using mono-lithium based initiators which were prepared by small molecule synthesis.In chapter 3,a novel polymer,unsaturated polytetrahydrofuran,was synthesized by condensation dehydration and halogenation in order to improve the polar modification of HTPB.In chapter 4 and 5,a series of random and alternating?,?-dihydroxy multiblock copolymers(MBCs)and hydroxyl-terminated hyperbranched copolymer were synthesized,which combined with ring-opening metathesis polymerization(ROMP),cationic ring-opening polymerization(CROP),anionic ring opening polymerization(AROP),hydroxyl-terminated polymers'modification,allyl alcohol dehydration condensation and thiol-ene click chemistry.In chapter 6,a series of side-chain functional polytetrahydrofuran derivatives were prepared by functionalized modification of unsaturated polytetrahydrofuran with the thiol-ene click reaction induced via blue light.The main research content and results are summarized as follows:(1)3-tert-butyldimethysilyloxy-1-propyllithium(t BDMSOPr Li)and3-triisopropylsilyloxy-1-propyllithium(TIPSOPr Li)used as initiators of anionic polymerization were designed and prepared.The structure of TIPSOPr Li was characterized using nuclear magnetic resonance(NMR)with an“indirect method”.Then,HTPB was prepared with 1,3-butadiene as monomer and those two mono-lithium based initiators via anionic polymerization.The microstructure of HTPB was characterized by Fourier transform infrared spectroscopy(FT-IR),NMR,and size-exclusion chromatography coupled with multi-angle laser light scattering(SEC-MALLS),and the content of 1,4 unit of HTPB was also studied using integral in the ¹H NMR spectrum.Thes results showed that the content of1,4 unit in HTPB synthesized by TIPSOPr Li as initators reached up to 90.7%,which was higher than the content of 1,4 unit in HTPB prepared by t BDMSOPr Li as initators.In order to study the influence of steric structural factors of mono-lithium based anionic initiator on 1,4unit content of hydroxyl terminated polybutadiene,a series of precursors with different steric volume were designed and synthesized.By using the prepared initiators,HTPB was synthesized via anionic polymerization of 1,3-butadiene.The structure-function relationship of 1,4 unit content of HTPB and initiator's steric volume were studied.It was found that the content of 1,4 unit in HTPB was markedly increased with the increase in initiator's steric volume,that the content of 1,4 unit of HTPB can upgrade to 92.4%.(2)A new polymer,poly(2-butenediol)(PBD),was prepared via polycondensation of cis-1,4-butenediol using[Cp Ru(CH₃CN)₃]PF₆/quinaldic acid as catalysts.The microstructure of PBD was studied using FT-IR,NMR,SEC-MALLS.The results showed that the molecular weight of PBDwas up to 4,600 g/mol and the molecular weight distribution was 1.63.The results also showed that trans-1,4 units and 1,2 units in PBD backbone is 94%and 6%,respectively.In addition,the compatibility test showed that PBD and energetic materials had good compatibility.PBD was also obtained via polycondensation using cis-1,4-butenediol and trans-1,4-butenediol as monomers.SEC-MALLS tests showed that the molecular weight of PBD was up to 5200 g/mol,and molecular weight distribution was 1.43.The polymerization process and polymerization mechanism for synthesis of PBD were lucubrated.At the same time,polylactide-b-PBD-b-polylactide triblock copolymer was also synthesized using PBD as macromolecular initiator.(3)?,?-dihydroxy Polycyclooctadiene(PCOD)was prepared by ROMP polymerization;?,?-dihydroxy PTHF was prepared via CROP polymerization;?,?-dihydroxy PEG was obtained by macromolecular end group modification;PEG-b-PTHF-b-PEG triblock copolymer was prepared via AROP polymerization.Using those polymers as macromonomers,we report a new strategy to synthesize random and alternating multiblock copolymers(MBCs)by the polycondensation of macromonomers'terminal hydroxyl groups using[Cp Ru(CH₃CN)₃]PF₆/quinaldic acid as the catalyst.Thoses MBCs included random MBCs of HTPB and PCOD(HTPB-ran-PCOD),random MBCs of PCOD and PBD(PCOD-ran-PBD),random MBCs of PEG and PTHF(PEG-ran-PTHF)and alternating MBCs of PEG and PTHF(PEG-alt-PTHF).The relationship between the reaction time and number averaged molecular weight(M_n)or molecular weight distribution(M_w/M_n)of MBCs was studied.The results showed that the M_n of MBCs increased to the maximum and then decreased with increasing reaction time;in contrast,the molecular weight distribution of MBCs decreased to the minimum and then increased with the last reaction time.(4)Hydroxyl-terminated hyperbranched polyethers containing double bonds(HTHP 1)were synthesized via cationic ring-opening polymerization.Then,through thiol-ene“click”reaction,hydroxyl-terminated hyperbranched polyethers containing carboxyl groups(HTHP 2)was obtained via reaction of double bond and 3-mercaptopropionic acid.The differential scanning calorimeter(DSC)test showed that those two hyperbranched polyethers were completely amorphous.The pH-responsive behavior of HTHP 1 and HTHP 2 was also studied.The results showed that HTHP 1 did not contain any ionizable groups and so it was not pH responsive.In case of HTHP 2,due to the incorporation of carboxyl group,it could ionize to generate H⁺at suitable pH value,and so it showed good pH responsiveness.Thermoresponsive phase transition behavior of the HTHP 1 and HTHP 2 was tested by UV–Vis approach.The results indicated that HTHP 1 and HTHP 2 all had obvious thermoresponsive phase transition behavior,and meanwhile the lower critical solution temperature(LCST)of HTHP 1 and HTHP 2 was dependence on concentration.The relationship between the LCST of HTHP 2 and pH values was also studied.By regulating the solution pH value range 3.0–5.2,LCST of HTHP 2 could be changed from 12.8 to 68.0?.(5)A series of side-chain functionalized PTHF derivatives were synthesized via the blue-light photocatalytic thiol-ene“click”reaction with PBD as macromolecular backbone.Double bonds in backbone of PBD modified into different pendant functionality side groups by thiol-ene“click”reaction obtaining different side-chain functionalized PTHF derivatives.Those PTHF derivatives respectively are side groups of PTHF derivatives contain hydroxyl groups(PTHF_OH),butyl groups(PTHF_but),carboxyl groups(PTHF_acid)and short chain of PEG(PTHF_mPEG).The research results showed that PTHF_OH and PTHF_acid were completely amorphous,and the glass transition temperatures of PTHF_OH and PTHF_acid were-36.5? and-61.3? respectively.PTHF_acid had obvious pH responsive behavior.The PTHF_mPEG could obtain backbone-thermoresponsive behavior through controling the chain segments of mPEG.