CURE CHARACTERISTICS OF HYDROXYL TERMINATED POLYBUTADIENE PREPOLYMER WITH BLOCKED TOLUENE DIISOCYANATE-Ⅱ

Cure characteristics of hydroxyl terminated polybutadiene (HTPB) prepolymer with avariety of blocked toluene diisocyanate (TDI) in the presence of triethylamine (TEA) andchloroacetic acid catalyst are reported. Phenol, thiophenol, p-chloropheno1, p-nitrophenol,p-cresol, resorcinol, naphthols, caprolactam and butylated-hydroxytoluene were used as blockingagents. Viscosity measurements have been carried out using a mixture of HTPB and blocked TDIin cyclohexanone in the presence of the catalysts at 50℃ and 60℃ using Haake rotational vis-cometer. Viscosity measurements have also been carried out with 50% solids such as ammonium sulphate along with HTPB and TDI adduct.

Composite Solid Rocket Propellant Based on GAP Polyurethane Matrix with Different Binder Contents

Different GAP-based CSRP samples with different binder contents were prepared and compared with that of conventional HTPB propellant.The crosslinker mixture of trimethylol propane(TMP)and butane diol(BD)was used in the GAP matrix beside the addition of dibutyltin dilaurate(DBTDL)to ensure cross-linking and curing completion of the prepared CSRP.The viscosity and hardness of all prepared formulations were monitored continuously during the curing process.The mechanical characteristics of cured samples were tested.The burning rate at operating pressure and specific impulse were measured,while the theoretical specific impulse(I sp)was calculated by ICT code and compared with the measured results.According to the results,DOA was found to be a suitable plasticizer for GAP when using in propellant.The mechanical properties of CSRP with 25%GAP can produce the optimum mechanical behavior,which is close to that of HTPB-based CSRP.The optimum GAP-based formulation is one candidate to replace the traditional HTPB-based CSRP with high burning rate for some applications.

Highly chemoselective lipase from Candida sp.99-125 catalyzed ring-opening polymerization for direct synthesis of thiol-terminated poly(e-caprolactone)

Lipase from Candida sp.99-125 catalyzed ring-opening polymerization of e-caprolactone in the presence of 6-mercapto-1-hexanol was presented as a new metal-free approach for direct synthesis of welldefined thiol-terminated poly（e-caprolactone）.Remarkably,high chemoselectivity of lipase from Candida sp.99-125 toward hydroxyl and thiol was exhibited and quantitative thiol fidelity over 90% was achieved.The tedious protecting/deprotecting steps for thiol and metal residue were avoided.The polymerizations with around 70% monomer conversion were conducted in bulk and toluene at relative low temperature of 40 ℃.Number–average molecular weight of resulted polymers ranged from 3000 to4700 Da by changing the feed ratio between monomer and initiator.The structures of obtained thiolterminated poly（e-caprolactone） were demonstrated by combining NMR and SEC analyses.

A study of solid ramjet fuel containing boron–magnesium mixtures

Solid fuel ramjets (SFRJ) are known for their operational simplicity and high specific impulse. The performance of the SFRJ propulsion system is directly tied to the energy density and combustion behavior of the fuel. A typical solid fuel used in a ramjet application is a collection of metal particles suspended in a polymeric binder. Boron is the ubiquitous candidate when considering metal additives for fuels due to an impressive 122.5 kJ/cm3 energy density. However, boron requires long residence times in combustors due to its high melting and boiling points. Magnesium appears to be a natural complement to boron;while possessing a lower energy density (42.1 kJ/cm3), it burns with a high flame temperature and readily reacts in combustion with a low melting point. In this study, several HTPB–boron–magnesium fuels are studied on a small scale to evaluate performance for ramjet application. Holography experiments are conducted, as well as laser ignition tests, to study particle behavior just above the fuel surface. Small, center-perforated fuel grains are examined in a direct-connect SFRJ test stand configuration to measure ignition temperatures and performance parameters. Combustion efficiency of the HTPB–boron–magnesium fuel is found to significantly increase for one of the fuels studied.