Controlled release of TDI and hence the cure characteristics of several blocked TDI with HTPB are reported. The reactions were followed through viscosity measurements as a function of time and temperature under the ca...Controlled release of TDI and hence the cure characteristics of several blocked TDI with HTPB are reported. The reactions were followed through viscosity measurements as a function of time and temperature under the catalytic influence of triethylamine. The effect of nature of substituents present on the end capping substrate, temperature, solvent, basicity of catalyst and kinetics thereon have been studied.展开更多
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...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.展开更多
The commercial vinyl ester resins(VER)was modified by diphenylmethane diisocyanate(MDI)to enhance its toughness,which is called MVER.Hexamethylene diisocyanate(HDI),a common curing agent for polyurethane(PU),was found...The commercial vinyl ester resins(VER)was modified by diphenylmethane diisocyanate(MDI)to enhance its toughness,which is called MVER.Hexamethylene diisocyanate(HDI),a common curing agent for polyurethane(PU),was found to be a reactive agent for MVER and can contribute to the toughness of MVER.Based on present experiment results,the crosslinking mechanism of MVER and HDI system is very similar to that of PU.The FTIR result shows the-NCO of HDI can react with the-OH of MVER.The microstructure of material prepared by MVER and HDI was characterized by NMR,and it was revealed that the unique microstructure leads to the good performances.The different content of HDI has an influence on the microstructure,and the microstructure gradually reduces the toughness and mechanical performances of the MVER cured with increasing concentration of reactive curing agent(HDI).This feature is consistent with a maximum in toughness as a function of the additive(HDI)content,followed by a rapid deterioration in toughness at higher concentrations.The toughness exhibits the maximum at such an HDI concentration(20wt%).Therefore,the special curing agent(HDI)and reactive mode is very important to the microstructure and mechanical properties of material.Furthermore,there should be other reactions which contribute to the curing and microstructure of the material,which needs the further research.展开更多
Organic-inorganic hybrid</span><b> </b><span style="font-family:Verdana;">network polymers have been synthesized by addition reaction of a thiol-functionalized random type silsesquiox...Organic-inorganic hybrid</span><b> </b><span style="font-family:Verdana;">network polymers have been synthesized by addition reaction of a thiol-functionalized random type silsesquioxane (SQ109) and alkyl diacrylate or diisocyanate compounds. Thiol-ene reaction of SQ109 and 1,4-butanediol diacrylate (BDA) successfully yield porous polymer in toluene initiated by azobis</span></span><span style="font-family:Verdana;">(</span><span style="font-family:Verdana;">isobutyronitrile</span><span style="font-family:Verdana;">)</span><span style="font-family:Verdana;"> (AIBN) at 60</span><span style="font-family:Verdana;">°</span><span style="font-family:Verdana;">C. Morphology of the porous polymers was composed by connected globules, and the diameter of the globules decreased with increasing in the monomer concentration </span><span style="font-family:Verdana;">of</span><span style="font-family:Verdana;"> the reaction </span><span style="font-family:Verdana;">system</span><span style="font-family:""><span style="font-family:Verdana;">. By contrast, the reaction with 1,6-hexanediol diacrylate or </span><span style="font-family:Verdana;">1,5-hexadiene yielded homogeneous clear gels. Thermal analyses of SQ109-BDA</span><span style="font-family:Verdana;"> porous polymers indicated that thermal degradation of ester groups of BDA in the polymer network occurred at around 300</span></span><span style="font-family:Verdana;">°</span><span style="font-family:Verdana;">C. The porous polymer was also obtained </span><span style="font-family:Verdana;">by</span><span style="font-family:Verdana;"> the reaction </span><span style="font-family:Verdana;">using</span><span style="font-family:""><span style="font-family:Verdana;"> a photo-initiator (Irugacure184) at room temperature, and showed higher Young’s modulus than the corresponding porous polymer obtained with the reaction with AIBN due to the small size of </span><span style="font-family:Verdana;">the globules. Young’s modulus of SQ109-BDA porous polymer increased</span><span style="font-family:Verdana;"> with </span><span style="font-family:Verdana;">increasing in the monomer concentration </span></span><span style="font-family:Verdana;">of</span><span style="font-family:Verdana;"> the reaction systems. Thioliso</span><span style="font-family:""><span style="font-family:Verdana;">cyanate addition reactions between SQ109 </span><span style="font-family:Verdana;">and hexamethylene diisocyanate (HDI) or methylenediphenyl 4,4’-diisocyanate</span><span style="font-family:Verdana;"> (MDI) were investigated to obtain network polymers. The reactions in toluene yielded the corresponding homogeneous clear gels. By contrast the reactions in a mixed solvent of toluene (50 vol.%) and </span><i><span style="font-family:Verdana;">N,N</span></i><span style="font-family:Verdana;">-dimethylformamide (50 vol.%) produced porous polymers. The morphology of the porous polymers was composed by connected </span><span style="font-family:Verdana;">globules or aggregated particles. The size of globules and particles in the</span><span style="font-family:Verdana;"> SQ109-HDI porous polymers was larger </span><span style="font-family:Verdana;">than </span></span><span style="font-family:Verdana;">those</span><span style="font-family:Verdana;"> in the SQ109-MDI porous polymers. Thermal degradation of SQ109-HDI and SQ109-MDI porous polymers</span><span style="font-family:Verdana;"> started at round 260</span><span style="font-family:Verdana;">°</span><span style="font-family:""><span style="font-family:Verdana;">C and showed </span><span style="font-family:Verdana;">endothermic peak at around 350</span></span><span style="font-family:Verdana;">°</span><span style="font-family:Verdana;">C derived from degradation of </span><span style="font-family:Verdana;">thio-urethane bond.展开更多
1,5-Pentamethylene diisocyanate, a novel aliphatic diisocyanate formed from bio-based 1,5-pentamethylenediamine, has been used as a hard segmented material to synthesize polyurethane. In this study, several waterborne...1,5-Pentamethylene diisocyanate, a novel aliphatic diisocyanate formed from bio-based 1,5-pentamethylenediamine, has been used as a hard segmented material to synthesize polyurethane. In this study, several waterborne polyurethane (WPU) dispersions have been successfully prepared by a prepolymer process from 1,5-pentamethylene diisocyanate poly(polyether) with different NCO/OH ratios and 1,6-hexanediol (HDO)/dimethylol propionic acid (DMPA) molar ratios. The Fourier transfonn infrared (FTIR) spectra, thermogravimetric analysis, differential scanning calorimetry, X-ray diffiraction, and a mechanical tensile test were used to investigate the structures, thermal stability, phase separation, crystallinity, mechanical properties, and adhesive performance of the WPU dispersions. The FTIR results indicate that the degree of hydrogen bonding and the numbers of urea groups increase as the NCO/OH ratio and HDO/DMPA molar ratio increase. Furthermore, the phase separation increases and the thermal stability decreases as the NCO/OH ratio increases or the HDO/DMPA molar ratio decreases. Finally, WPU3.0-2.4 (NCO/OH = 3, HDO/DMPA = 2.4) exhibits a maximum tensile strength and shear strength, pointing to its possible use as an adhesive. These results could provide a very valuable reference for industrial applications of WPU.展开更多
Cadaverine is an important C5 platform chemical with a wide range of industrial applications.However,the cadaverine inhibition on the fermenting strain limited its industrial efficiency of the strain.In this study,we ...Cadaverine is an important C5 platform chemical with a wide range of industrial applications.However,the cadaverine inhibition on the fermenting strain limited its industrial efficiency of the strain.In this study,we report an engineered Escherichia coli strain with high cadaverine productivity that was generated by developing a robust host coupled with metabolic engineering to mitigate cadaverine inhibition.First,a lysine producing E.coli was treated with a combination of radiation(ultraviolet and visible spectrum)and ARTP(atmospheric and room temperature plasma)mutagenesis to obtain a robust host with high cadaverine tolerance.Three mutant targets including HokD,PhnI and PuuR are identified for improved cadaverine tolerance.Further transcriptome analysis suggested that cadaverine suppressed the synthesis of ATP and lysine precursor.Accordingly,the related genes involved in glycolysis and lysine precursor,as well as cadaverine exporter was engineered to release the cadaverine inhibition.The final engineered strain was fed-batch cultured and a titer of 58.7 g/L cadaverine was achieved with a yield of 0.396 g/g,both of which were the highest level reported to date in E.coli.The bio-based cadaverine was purified to>99.6%purity,and successfully used for the synthesis of polyurethane precursor 1,5-pentamethylene diisocyanate(PDI)through the approach of carbamate decomposition.展开更多
A novel polycarbonate urethane was synthesized by the two-stage solution process of diisocyanates with polycarbonate diols(PCDL),in which PCDL,1,4-butanediol(BD) and mixture of 4,4'-methylenediphenyl diisocy-anate...A novel polycarbonate urethane was synthesized by the two-stage solution process of diisocyanates with polycarbonate diols(PCDL),in which PCDL,1,4-butanediol(BD) and mixture of 4,4'-methylenediphenyl diisocy-anate and hexamethylene diisocyanate(HDI) were soft segment,chain extender and rigid segment,respectively.The structures were characterized by using FTIR and 1H-NMR.The thermoanalysis and mechanical properties of products were measured by means of DSC,TG and other systems.The result shows that an important technological thrust is the development of polymeric materials with improved mechanical characteristics.With the increase in content of HDI component,the elongation at break point increases quickly and decomposition temperature decreases.The DSC/TG curves indicate that a phase division exists in the structure of polycarbonate urethanes.Thermal decomposition occurs at two temperature levels because their rigid and soft chain segments correspond to different glass transition domains,respectively.This paper demonstrates that the mechanical properties of polycarbonate urethane can be controlled by changing the ratio of raw materials.展开更多
Aging of a solid composite propellant containing HTPB/AP/AL was performed in order to validate the conformance of the accelerated aging data to the Arrhenius law. The main objective of the work was to examine the infl...Aging of a solid composite propellant containing HTPB/AP/AL was performed in order to validate the conformance of the accelerated aging data to the Arrhenius law. The main objective of the work was to examine the influence of the aziridine bonding agents family on the propellant aging. Aging of the prepared propellant samples was conducted as follows: 1. Four samples, one free of bonding agents, and three containing aziridine based bonding agents MAPO,HX-752, MAT4 were aged at 65°C. 2. Another four samples based on HX-752, MAT4 with different curing agents were aged at 65°C. The measured mechanical properties of the free bonding agent propellant samples were very far from the specifications and this illustrates the importance of the bonding agents in both the preparation and the aging phases.The prepared bonding agent "MAT4" gave remarkable improvements of the mechanical properties comparing with HX-752 and MAPO. The aziridine bonding agents family inhibited the rate of decomposition of the propellant during the aging periods and supported the propellant matrix against decomposition at the elevate temperatures. Using of HMDI as curing agent gave slight better mechanical properties to the IPDI.展开更多
Polyurethane-imide elastomers (PUIEs) are formed from isocyanate, polyol, acid anhydride, and diamine by liquid polymerization. Unfortunately, many of the diamines have rarely been applied to the formation of PUIEs. H...Polyurethane-imide elastomers (PUIEs) are formed from isocyanate, polyol, acid anhydride, and diamine by liquid polymerization. Unfortunately, many of the diamines have rarely been applied to the formation of PUIEs. Hence, investigating the effect of diamines on PUIEs remains a challenge in polymer chemistry. Herein, PUIEs prepared from 4,4'-diphenylmethane diisocyanate (MDI), polytetramethylene glycol (Mw: 1000), pyromellitic dianhydride, and aromatic diamines (such as p-phenylene diamine, 4,4'-oxydianiline, and 1,3-bis(4-aminophenoxy)benzene), and aliphatic diamines (such as 1,2-ethylene diamine, 1,6-hexamethylene diamine, and 1,12-dodecamethylene diamine) were synthesized by liquid polymerization. The morphologies and the chemical, thermal, and mechanical properties of the various PUIEs were investigated. The obtained elastomeric sheets were characterized in terms of the following tests and methods: solubility and swelling tests, X-ray diffraction and differential scanning calorimetry, dynamic mechanical analysis and thermogravimetric analysis, tensile tests, nuclear magnetic resonance spectroscopy, infrared spectroscopy, atomic force microscopy, contact angle microscopy, and scanning electron展开更多
The effects of plasticizers,antioxidants and burning rate modifiers on the aging performance of the composite solid propellant based on hydroxyl-terminated polybutadiene(HTPB)/hexamethylene diisocyanate(HMDI)were expl...The effects of plasticizers,antioxidants and burning rate modifiers on the aging performance of the composite solid propellant based on hydroxyl-terminated polybutadiene(HTPB)/hexamethylene diisocyanate(HMDI)were explored by apply-ing an accelerated aging program for 90 day at 70 ℃. The HTPB propellant matrix with the diisooctyl sebacate(DOS)as plasti-cizers and diisooctyl azelate(DOZ), antioxidants as N,N ′-Diphenyl-p-phenylenediamine(AO) and 2,2′-methylenebis(4-methyl-6-tert-butylphenol)(cyanox 2246)and burning rate modifiers as barium ferrite(BF),copper chromites(CC)and fer-ric oxide(FO)were varied. Results show that sample(S1)which based on DOS decreases the stress value and increases the strain value which considered to be an excellent start for aging program. Sample(S3)containing AO presents the higher resis-tance to oxidation showing the better performance that reflects on increasing the shelf life of the composite solid propellant mo-tor. Sample(S5)which based on BF enhances the ballistic performance among over the other tested two samples. The accelerat-ed aging program allowed us to estimate the motor in-service lifetime.展开更多
It is known that large amounts of residual lignin are generated in the pulp and paper industry.A new alternative for Kraft lignin valorization,which consists of first a chemical modification using a diisocyanate and t...It is known that large amounts of residual lignin are generated in the pulp and paper industry.A new alternative for Kraft lignin valorization,which consists of first a chemical modification using a diisocyanate and then the efficient dispersion in castor oil to achieve stable gel-like systems,is proposed in this work.Rheological properties and microstructure of these materials were determined by means of small amplitude oscillatory shear tests and viscous flow measurements and atomic force microscopy observations,respectively.Moreover,both standardized penetration tests and tribological assays,usually performed in the lubricant industry,were carried out to evaluate the performance characteristics as lubricating greases.Linear viscoelasticity functions are affected by the lignin/diisocyanate ratio and thickener concentration.The thermorheological response evidenced a softening temperature of around 105°C.The microstructure of these gel-like dispersions is composed of interconnected thin fibers,homogeneously distributed in castor oil.Moreover,the NCO-functionalized lignin gel-like dispersions studied show lower friction coefficients than traditional lubricating greases.展开更多
文摘Controlled release of TDI and hence the cure characteristics of several blocked TDI with HTPB are reported. The reactions were followed through viscosity measurements as a function of time and temperature under the catalytic influence of triethylamine. The effect of nature of substituents present on the end capping substrate, temperature, solvent, basicity of catalyst and kinetics thereon have been studied.
文摘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.
基金Funded by the National Natural Science Foundation of China(51809017)the Basic Scientific Research Project of Public Welfare Research Institutes of the Central Level(CKSF2017060/CL,CKSF2017020/CL,and CKSF2019187/CL)the Financial Science and Technology Project of Xinjiang Corps(2020AB010)。
文摘The commercial vinyl ester resins(VER)was modified by diphenylmethane diisocyanate(MDI)to enhance its toughness,which is called MVER.Hexamethylene diisocyanate(HDI),a common curing agent for polyurethane(PU),was found to be a reactive agent for MVER and can contribute to the toughness of MVER.Based on present experiment results,the crosslinking mechanism of MVER and HDI system is very similar to that of PU.The FTIR result shows the-NCO of HDI can react with the-OH of MVER.The microstructure of material prepared by MVER and HDI was characterized by NMR,and it was revealed that the unique microstructure leads to the good performances.The different content of HDI has an influence on the microstructure,and the microstructure gradually reduces the toughness and mechanical performances of the MVER cured with increasing concentration of reactive curing agent(HDI).This feature is consistent with a maximum in toughness as a function of the additive(HDI)content,followed by a rapid deterioration in toughness at higher concentrations.The toughness exhibits the maximum at such an HDI concentration(20wt%).Therefore,the special curing agent(HDI)and reactive mode is very important to the microstructure and mechanical properties of material.Furthermore,there should be other reactions which contribute to the curing and microstructure of the material,which needs the further research.
文摘Organic-inorganic hybrid</span><b> </b><span style="font-family:Verdana;">network polymers have been synthesized by addition reaction of a thiol-functionalized random type silsesquioxane (SQ109) and alkyl diacrylate or diisocyanate compounds. Thiol-ene reaction of SQ109 and 1,4-butanediol diacrylate (BDA) successfully yield porous polymer in toluene initiated by azobis</span></span><span style="font-family:Verdana;">(</span><span style="font-family:Verdana;">isobutyronitrile</span><span style="font-family:Verdana;">)</span><span style="font-family:Verdana;"> (AIBN) at 60</span><span style="font-family:Verdana;">°</span><span style="font-family:Verdana;">C. Morphology of the porous polymers was composed by connected globules, and the diameter of the globules decreased with increasing in the monomer concentration </span><span style="font-family:Verdana;">of</span><span style="font-family:Verdana;"> the reaction </span><span style="font-family:Verdana;">system</span><span style="font-family:""><span style="font-family:Verdana;">. By contrast, the reaction with 1,6-hexanediol diacrylate or </span><span style="font-family:Verdana;">1,5-hexadiene yielded homogeneous clear gels. Thermal analyses of SQ109-BDA</span><span style="font-family:Verdana;"> porous polymers indicated that thermal degradation of ester groups of BDA in the polymer network occurred at around 300</span></span><span style="font-family:Verdana;">°</span><span style="font-family:Verdana;">C. The porous polymer was also obtained </span><span style="font-family:Verdana;">by</span><span style="font-family:Verdana;"> the reaction </span><span style="font-family:Verdana;">using</span><span style="font-family:""><span style="font-family:Verdana;"> a photo-initiator (Irugacure184) at room temperature, and showed higher Young’s modulus than the corresponding porous polymer obtained with the reaction with AIBN due to the small size of </span><span style="font-family:Verdana;">the globules. Young’s modulus of SQ109-BDA porous polymer increased</span><span style="font-family:Verdana;"> with </span><span style="font-family:Verdana;">increasing in the monomer concentration </span></span><span style="font-family:Verdana;">of</span><span style="font-family:Verdana;"> the reaction systems. Thioliso</span><span style="font-family:""><span style="font-family:Verdana;">cyanate addition reactions between SQ109 </span><span style="font-family:Verdana;">and hexamethylene diisocyanate (HDI) or methylenediphenyl 4,4’-diisocyanate</span><span style="font-family:Verdana;"> (MDI) were investigated to obtain network polymers. The reactions in toluene yielded the corresponding homogeneous clear gels. By contrast the reactions in a mixed solvent of toluene (50 vol.%) and </span><i><span style="font-family:Verdana;">N,N</span></i><span style="font-family:Verdana;">-dimethylformamide (50 vol.%) produced porous polymers. The morphology of the porous polymers was composed by connected </span><span style="font-family:Verdana;">globules or aggregated particles. The size of globules and particles in the</span><span style="font-family:Verdana;"> SQ109-HDI porous polymers was larger </span><span style="font-family:Verdana;">than </span></span><span style="font-family:Verdana;">those</span><span style="font-family:Verdana;"> in the SQ109-MDI porous polymers. Thermal degradation of SQ109-HDI and SQ109-MDI porous polymers</span><span style="font-family:Verdana;"> started at round 260</span><span style="font-family:Verdana;">°</span><span style="font-family:""><span style="font-family:Verdana;">C and showed </span><span style="font-family:Verdana;">endothermic peak at around 350</span></span><span style="font-family:Verdana;">°</span><span style="font-family:Verdana;">C derived from degradation of </span><span style="font-family:Verdana;">thio-urethane bond.
基金the National Natural Science Foundation of China (Grant Nos. 21576134 and 51503097)the National Key Research and Development Program of China (Grant No. 2016YFA0204300)the Jiangsu Province Natural Science Foundation (No. BK20150244).
文摘1,5-Pentamethylene diisocyanate, a novel aliphatic diisocyanate formed from bio-based 1,5-pentamethylenediamine, has been used as a hard segmented material to synthesize polyurethane. In this study, several waterborne polyurethane (WPU) dispersions have been successfully prepared by a prepolymer process from 1,5-pentamethylene diisocyanate poly(polyether) with different NCO/OH ratios and 1,6-hexanediol (HDO)/dimethylol propionic acid (DMPA) molar ratios. The Fourier transfonn infrared (FTIR) spectra, thermogravimetric analysis, differential scanning calorimetry, X-ray diffiraction, and a mechanical tensile test were used to investigate the structures, thermal stability, phase separation, crystallinity, mechanical properties, and adhesive performance of the WPU dispersions. The FTIR results indicate that the degree of hydrogen bonding and the numbers of urea groups increase as the NCO/OH ratio and HDO/DMPA molar ratio increase. Furthermore, the phase separation increases and the thermal stability decreases as the NCO/OH ratio increases or the HDO/DMPA molar ratio decreases. Finally, WPU3.0-2.4 (NCO/OH = 3, HDO/DMPA = 2.4) exhibits a maximum tensile strength and shear strength, pointing to its possible use as an adhesive. These results could provide a very valuable reference for industrial applications of WPU.
基金This work is supported by the National Key R&D Program of China(2021YFC2100800)Key Research and Development Program(Social Development)Project of Jiangsu Province(BE2018730)the Jiangsu Synergetic Innovation Center for Advanced Bio-Manufacture(XTE1844 and XTB1806).
文摘Cadaverine is an important C5 platform chemical with a wide range of industrial applications.However,the cadaverine inhibition on the fermenting strain limited its industrial efficiency of the strain.In this study,we report an engineered Escherichia coli strain with high cadaverine productivity that was generated by developing a robust host coupled with metabolic engineering to mitigate cadaverine inhibition.First,a lysine producing E.coli was treated with a combination of radiation(ultraviolet and visible spectrum)and ARTP(atmospheric and room temperature plasma)mutagenesis to obtain a robust host with high cadaverine tolerance.Three mutant targets including HokD,PhnI and PuuR are identified for improved cadaverine tolerance.Further transcriptome analysis suggested that cadaverine suppressed the synthesis of ATP and lysine precursor.Accordingly,the related genes involved in glycolysis and lysine precursor,as well as cadaverine exporter was engineered to release the cadaverine inhibition.The final engineered strain was fed-batch cultured and a titer of 58.7 g/L cadaverine was achieved with a yield of 0.396 g/g,both of which were the highest level reported to date in E.coli.The bio-based cadaverine was purified to>99.6%purity,and successfully used for the synthesis of polyurethane precursor 1,5-pentamethylene diisocyanate(PDI)through the approach of carbamate decomposition.
基金Supported by International Cooperation from Ministry of Science and Technology of China (No.2008DFA51170)Program for New Century Excellent Talents (NCET) in University,Ministry of Education,China,and Scientific Research Foundation for Returned Overseas Chinese Scholars,Ministry of Education,China
文摘A novel polycarbonate urethane was synthesized by the two-stage solution process of diisocyanates with polycarbonate diols(PCDL),in which PCDL,1,4-butanediol(BD) and mixture of 4,4'-methylenediphenyl diisocy-anate and hexamethylene diisocyanate(HDI) were soft segment,chain extender and rigid segment,respectively.The structures were characterized by using FTIR and 1H-NMR.The thermoanalysis and mechanical properties of products were measured by means of DSC,TG and other systems.The result shows that an important technological thrust is the development of polymeric materials with improved mechanical characteristics.With the increase in content of HDI component,the elongation at break point increases quickly and decomposition temperature decreases.The DSC/TG curves indicate that a phase division exists in the structure of polycarbonate urethanes.Thermal decomposition occurs at two temperature levels because their rigid and soft chain segments correspond to different glass transition domains,respectively.This paper demonstrates that the mechanical properties of polycarbonate urethane can be controlled by changing the ratio of raw materials.
文摘Aging of a solid composite propellant containing HTPB/AP/AL was performed in order to validate the conformance of the accelerated aging data to the Arrhenius law. The main objective of the work was to examine the influence of the aziridine bonding agents family on the propellant aging. Aging of the prepared propellant samples was conducted as follows: 1. Four samples, one free of bonding agents, and three containing aziridine based bonding agents MAPO,HX-752, MAT4 were aged at 65°C. 2. Another four samples based on HX-752, MAT4 with different curing agents were aged at 65°C. The measured mechanical properties of the free bonding agent propellant samples were very far from the specifications and this illustrates the importance of the bonding agents in both the preparation and the aging phases.The prepared bonding agent "MAT4" gave remarkable improvements of the mechanical properties comparing with HX-752 and MAPO. The aziridine bonding agents family inhibited the rate of decomposition of the propellant during the aging periods and supported the propellant matrix against decomposition at the elevate temperatures. Using of HMDI as curing agent gave slight better mechanical properties to the IPDI.
文摘Polyurethane-imide elastomers (PUIEs) are formed from isocyanate, polyol, acid anhydride, and diamine by liquid polymerization. Unfortunately, many of the diamines have rarely been applied to the formation of PUIEs. Hence, investigating the effect of diamines on PUIEs remains a challenge in polymer chemistry. Herein, PUIEs prepared from 4,4'-diphenylmethane diisocyanate (MDI), polytetramethylene glycol (Mw: 1000), pyromellitic dianhydride, and aromatic diamines (such as p-phenylene diamine, 4,4'-oxydianiline, and 1,3-bis(4-aminophenoxy)benzene), and aliphatic diamines (such as 1,2-ethylene diamine, 1,6-hexamethylene diamine, and 1,12-dodecamethylene diamine) were synthesized by liquid polymerization. The morphologies and the chemical, thermal, and mechanical properties of the various PUIEs were investigated. The obtained elastomeric sheets were characterized in terms of the following tests and methods: solubility and swelling tests, X-ray diffraction and differential scanning calorimetry, dynamic mechanical analysis and thermogravimetric analysis, tensile tests, nuclear magnetic resonance spectroscopy, infrared spectroscopy, atomic force microscopy, contact angle microscopy, and scanning electron
文摘The effects of plasticizers,antioxidants and burning rate modifiers on the aging performance of the composite solid propellant based on hydroxyl-terminated polybutadiene(HTPB)/hexamethylene diisocyanate(HMDI)were explored by apply-ing an accelerated aging program for 90 day at 70 ℃. The HTPB propellant matrix with the diisooctyl sebacate(DOS)as plasti-cizers and diisooctyl azelate(DOZ), antioxidants as N,N ′-Diphenyl-p-phenylenediamine(AO) and 2,2′-methylenebis(4-methyl-6-tert-butylphenol)(cyanox 2246)and burning rate modifiers as barium ferrite(BF),copper chromites(CC)and fer-ric oxide(FO)were varied. Results show that sample(S1)which based on DOS decreases the stress value and increases the strain value which considered to be an excellent start for aging program. Sample(S3)containing AO presents the higher resis-tance to oxidation showing the better performance that reflects on increasing the shelf life of the composite solid propellant mo-tor. Sample(S5)which based on BF enhances the ballistic performance among over the other tested two samples. The accelerat-ed aging program allowed us to estimate the motor in-service lifetime.
文摘It is known that large amounts of residual lignin are generated in the pulp and paper industry.A new alternative for Kraft lignin valorization,which consists of first a chemical modification using a diisocyanate and then the efficient dispersion in castor oil to achieve stable gel-like systems,is proposed in this work.Rheological properties and microstructure of these materials were determined by means of small amplitude oscillatory shear tests and viscous flow measurements and atomic force microscopy observations,respectively.Moreover,both standardized penetration tests and tribological assays,usually performed in the lubricant industry,were carried out to evaluate the performance characteristics as lubricating greases.Linear viscoelasticity functions are affected by the lignin/diisocyanate ratio and thickener concentration.The thermorheological response evidenced a softening temperature of around 105°C.The microstructure of these gel-like dispersions is composed of interconnected thin fibers,homogeneously distributed in castor oil.Moreover,the NCO-functionalized lignin gel-like dispersions studied show lower friction coefficients than traditional lubricating greases.