A submerged cavitation water jet(SCWJ)is an effective method to recycle solid propellant from obsolete solid engines by the breaking method.Solid propellant's breaking modes and mechanical process under SCWJ impac...A submerged cavitation water jet(SCWJ)is an effective method to recycle solid propellant from obsolete solid engines by the breaking method.Solid propellant's breaking modes and mechanical process under SCWJ impact are unclear.This study aims to understand those impact breaking mechanisms.The hydroxyl-terminated polybutadiene(HTPB)propellant was chosen as the research material,and a self-designed test system was used to conduct impact tests at four different working pressures.The high-speed camera characterized crack propagation,and the DIC method calculated strain change during the impact process.Besides,micro and macro fracture morphologies were characterized by scanning electron microscope(SEM)and computed tomography(CT)scanning.The results reveal that the compressive strain concentration region locates right below the nozzle,and the shear strain region distributes symmetrically with the jet axis,which increases to 4% at first 16th ms,the compressive strain rises to 2% and 6% in the axial and transverse direction,respectively.The two tensile cracks formed first at the compression strain concentrate region,and there generate many shear cracks around the tensile cracks,and those shear cracks that develop and aggregate cause the cracks to become wider and cut through the tensile cracks,forming the tensile-shear cracks and the impact parts eventually fail.The HTPB propellant forms a breaking hole shaped conical after impact 10 s.The mass loss increases by 17 times at maximum,with the working pressure increasing by three times.Meanwhile,the damage value of the breaking hole remaining on the surface increases by 7.8 times while 2.9 times in the depth of the breaking hole.The breaking efficiency is closely affected by working pressures.The failure modes of HTPB impacted by SCWJ are classified as tensile crack-dominated and tensile-shear crack-dominated damage mechanisms.展开更多
Shish kebab structure of cis-1 , 4-polybutadiene has been obtained by quiescent solution crystallization at suitable temperature. The morphology and growth mechanism of formation of shish kebab structure have been stu...Shish kebab structure of cis-1 , 4-polybutadiene has been obtained by quiescent solution crystallization at suitable temperature. The morphology and growth mechanism of formation of shish kebab structure have been studied in detail.The higher the molecular weight the faster the sample crystallizes.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
An azo-group containing polybutadiene macroinitiator was prepared by Pinner synthesis and characterized by IR, NMR, GPC, viscosity and elemental measurements. The macroinitiator was further use to polymerize acrylamid...An azo-group containing polybutadiene macroinitiator was prepared by Pinner synthesis and characterized by IR, NMR, GPC, viscosity and elemental measurements. The macroinitiator was further use to polymerize acrylamide (AAm) in benzene to form polybutadiene/polyacrylamide (PBD/PAAm) block copolymers. High conversion of AAm was obtained over a wide range of monomer/macroinitiator ratios. The PBD/PAAm block copolymers were found to have excellent solvent resistance.展开更多
The cross-metathesis degradation of poly(styrene-co-butadiene) (styrene, 30 wt%) (SB-1) and poly(styrene-co-butadiene) (styrene, 21 wt%) (SB- 2) in the presence of essential oils and d-limo-nene as chain transfer agen...The cross-metathesis degradation of poly(styrene-co-butadiene) (styrene, 30 wt%) (SB-1) and poly(styrene-co-butadiene) (styrene, 21 wt%) (SB- 2) in the presence of essential oils and d-limo-nene as chain transfer agents (CTAs) using Rualkylidene catalysts (PCy3)2(Cl)2Ru = CHPh (I) and (1,3-diphenyl-4,5-dihydroimidazol-2-ylidene) (PCy3)Cl2Ru=CHPh (II) was studied. Terpene-terminated butadiene oligomers and polystyrene blocks were obtained as products of the degradation of SB-1 and SB-2. Catalysts I and II showed high activity in the degradation of SB copolymers to produce the low molecular weight products (Mn = 276 - 335 g·mol-1) and yields ranging from 91% - 95%. The cross-metathesis degradation of copolymers in organic solvents and in citrus oils (mandarin, orange and lemon oils) proceeded with similar efficiency and resulted in the same molecular weight butadiene oligomers. According to GS/MS (EI) analysis, the main products of the degradation of SB-1 copolymer with d-limonene were limonene-terminated oligomers of series Am (m = 1 - 4).展开更多
High active catalyst systems for polymerization of butadiene may be obtained by combining MoCl,ORand proper aluminum alkyl.The conversion of 80% of butadiene can be achieved with 5x10-5 mole ofMoCl4OCH17per mole of bu...High active catalyst systems for polymerization of butadiene may be obtained by combining MoCl,ORand proper aluminum alkyl.The conversion of 80% of butadiene can be achieved with 5x10-5 mole ofMoCl4OCH17per mole of butadiene at 70℃ in hydrogenated gasoline.The polydispersity of the polymersin the range of 1.5—2.0 is carried out with the temperature of polymerization at 30—70℃.For the purpose ofregulating molecular weight and chain structure of the polymers allyl halides is satisfactory,among othersallyl iodide is the best.With increase of amount of allyl iodide,the molecular wieght of the polymers de-crease,the 1,2-units increase and the regularity of chain structure of the polymers rises.Some of the physicalproperties of the polymers are as follows:the content of 1,2-units,88——97%;limiting viscosity number,1.8——6.2（in 30℃,toluene）;glass temperature,-27——10℃:tensile yield strength,6.5——8.5（kg/cm2）;ultimate tensile strength,12——25（kg/cm2）and elongation at break,1700—2900%.展开更多
Morphologies,crystallization behavior and mechanical properties of polypropylene（PP）/syndiotactic 1,2-polybutadiene（s-1,2 PB）blends were investigated.Morphology observation shows the well dispersed domains of s-1,...Morphologies,crystallization behavior and mechanical properties of polypropylene（PP）/syndiotactic 1,2-polybutadiene（s-1,2 PB）blends were investigated.Morphology observation shows the well dispersed domains of s-1,2 PB in PP matrix with the rather small domain sizes from 0.1 to 0.5μm when the s-1,2 PB content increases from 5%to 20%（mass fraction）in the blends,and the phase structure tends to become co-continuous as s-1,2 PB content further increases.Crystallization temperature（Tc）of PP component in the blends is fluctuated with the variation of s-1,2 PB content in the blends.Compatibilization,to some extent,between the two components is inferred from the examination of both morphology and crystallization behavior.Improvement of impact strength of PP toughened by s-1,2 PB becomes significant only in the case of s-1,2 PB content above 20%（mass fraction）.展开更多
Objectives To investigate the possible role of amino-terminal pro-brain natriuretic peptide （NT-proBNP） in the occurrence of atrial fibrillation （AF） after coronary artery bypass grafting （CABG）. Methods This st...Objectives To investigate the possible role of amino-terminal pro-brain natriuretic peptide （NT-proBNP） in the occurrence of atrial fibrillation （AF） after coronary artery bypass grafting （CABG）. Methods This study group included 70 consecutive patients scheduled for elective off-pump CABG. The patients with ejection fraction （EF） less than 0. 30, history of AF, use of class Ⅰ or Ⅲ antiarrhythmic drug, implanted pacemaker, postoperative myocardial infarction or chest reopening for pericardial tamponade were excluded. Preoperative and postoperative serum NT-proBNP levels were measured by radioimmunoassay technique. Results Postoperative AF occurred in 15 patients （21.4%）; these patients had significantly higher median NT-proBNP levels when compared with those without AF after the operation （ P 〈 0. 01 ）. Using multivariate logistic regression analyses, an increase in NT-proBNP level after CABG was found to be independently associated with AF （ OR = 3.78, 95% IC = 1.81 - 4. 89, P 〈 0. 01 ）. Increased age, diabetes mellitus, preoperative use of β-blocker, proximal right coronary artery involvement, and longer operation time were al- so associated with AF. Conclusions These results indicated that AF was associated with higher NT-proBNP concentrations after off pump CABG; the increase in NT-proBNP after CABG may play an important role in the occurrence of AF after the operation. The further studies are needed to define the reason that lead to higher NT-proBNP concentrations among the patients who present AF after off pump CABG.展开更多
基金supported by the Program for National Defense Science and Technology Foundation Strengtheningthe Youth Foundation of Rocket Force University of Engineering(Grant No.2021QN-B014)。
文摘A submerged cavitation water jet(SCWJ)is an effective method to recycle solid propellant from obsolete solid engines by the breaking method.Solid propellant's breaking modes and mechanical process under SCWJ impact are unclear.This study aims to understand those impact breaking mechanisms.The hydroxyl-terminated polybutadiene(HTPB)propellant was chosen as the research material,and a self-designed test system was used to conduct impact tests at four different working pressures.The high-speed camera characterized crack propagation,and the DIC method calculated strain change during the impact process.Besides,micro and macro fracture morphologies were characterized by scanning electron microscope(SEM)and computed tomography(CT)scanning.The results reveal that the compressive strain concentration region locates right below the nozzle,and the shear strain region distributes symmetrically with the jet axis,which increases to 4% at first 16th ms,the compressive strain rises to 2% and 6% in the axial and transverse direction,respectively.The two tensile cracks formed first at the compression strain concentrate region,and there generate many shear cracks around the tensile cracks,and those shear cracks that develop and aggregate cause the cracks to become wider and cut through the tensile cracks,forming the tensile-shear cracks and the impact parts eventually fail.The HTPB propellant forms a breaking hole shaped conical after impact 10 s.The mass loss increases by 17 times at maximum,with the working pressure increasing by three times.Meanwhile,the damage value of the breaking hole remaining on the surface increases by 7.8 times while 2.9 times in the depth of the breaking hole.The breaking efficiency is closely affected by working pressures.The failure modes of HTPB impacted by SCWJ are classified as tensile crack-dominated and tensile-shear crack-dominated damage mechanisms.
文摘Shish kebab structure of cis-1 , 4-polybutadiene has been obtained by quiescent solution crystallization at suitable temperature. The morphology and growth mechanism of formation of shish kebab structure have been studied in detail.The higher the molecular weight the faster the sample crystallizes.
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This work was supported by the National Natural Science Foundation of China(Grant 2907200)
文摘An azo-group containing polybutadiene macroinitiator was prepared by Pinner synthesis and characterized by IR, NMR, GPC, viscosity and elemental measurements. The macroinitiator was further use to polymerize acrylamide (AAm) in benzene to form polybutadiene/polyacrylamide (PBD/PAAm) block copolymers. High conversion of AAm was obtained over a wide range of monomer/macroinitiator ratios. The PBD/PAAm block copolymers were found to have excellent solvent resistance.
文摘The cross-metathesis degradation of poly(styrene-co-butadiene) (styrene, 30 wt%) (SB-1) and poly(styrene-co-butadiene) (styrene, 21 wt%) (SB- 2) in the presence of essential oils and d-limo-nene as chain transfer agents (CTAs) using Rualkylidene catalysts (PCy3)2(Cl)2Ru = CHPh (I) and (1,3-diphenyl-4,5-dihydroimidazol-2-ylidene) (PCy3)Cl2Ru=CHPh (II) was studied. Terpene-terminated butadiene oligomers and polystyrene blocks were obtained as products of the degradation of SB-1 and SB-2. Catalysts I and II showed high activity in the degradation of SB copolymers to produce the low molecular weight products (Mn = 276 - 335 g·mol-1) and yields ranging from 91% - 95%. The cross-metathesis degradation of copolymers in organic solvents and in citrus oils (mandarin, orange and lemon oils) proceeded with similar efficiency and resulted in the same molecular weight butadiene oligomers. According to GS/MS (EI) analysis, the main products of the degradation of SB-1 copolymer with d-limonene were limonene-terminated oligomers of series Am (m = 1 - 4).
文摘High active catalyst systems for polymerization of butadiene may be obtained by combining MoCl,ORand proper aluminum alkyl.The conversion of 80% of butadiene can be achieved with 5x10-5 mole ofMoCl4OCH17per mole of butadiene at 70℃ in hydrogenated gasoline.The polydispersity of the polymersin the range of 1.5—2.0 is carried out with the temperature of polymerization at 30—70℃.For the purpose ofregulating molecular weight and chain structure of the polymers allyl halides is satisfactory,among othersallyl iodide is the best.With increase of amount of allyl iodide,the molecular wieght of the polymers de-crease,the 1,2-units increase and the regularity of chain structure of the polymers rises.Some of the physicalproperties of the polymers are as follows:the content of 1,2-units,88——97%;limiting viscosity number,1.8——6.2（in 30℃,toluene）;glass temperature,-27——10℃:tensile yield strength,6.5——8.5（kg/cm2）;ultimate tensile strength,12——25（kg/cm2）and elongation at break,1700—2900%.
基金the Natural Science Foundation of Heilongjiang Province,China(No.B2005-09).
文摘Morphologies,crystallization behavior and mechanical properties of polypropylene（PP）/syndiotactic 1,2-polybutadiene（s-1,2 PB）blends were investigated.Morphology observation shows the well dispersed domains of s-1,2 PB in PP matrix with the rather small domain sizes from 0.1 to 0.5μm when the s-1,2 PB content increases from 5%to 20%（mass fraction）in the blends,and the phase structure tends to become co-continuous as s-1,2 PB content further increases.Crystallization temperature（Tc）of PP component in the blends is fluctuated with the variation of s-1,2 PB content in the blends.Compatibilization,to some extent,between the two components is inferred from the examination of both morphology and crystallization behavior.Improvement of impact strength of PP toughened by s-1,2 PB becomes significant only in the case of s-1,2 PB content above 20%（mass fraction）.
文摘Objectives To investigate the possible role of amino-terminal pro-brain natriuretic peptide （NT-proBNP） in the occurrence of atrial fibrillation （AF） after coronary artery bypass grafting （CABG）. Methods This study group included 70 consecutive patients scheduled for elective off-pump CABG. The patients with ejection fraction （EF） less than 0. 30, history of AF, use of class Ⅰ or Ⅲ antiarrhythmic drug, implanted pacemaker, postoperative myocardial infarction or chest reopening for pericardial tamponade were excluded. Preoperative and postoperative serum NT-proBNP levels were measured by radioimmunoassay technique. Results Postoperative AF occurred in 15 patients （21.4%）; these patients had significantly higher median NT-proBNP levels when compared with those without AF after the operation （ P 〈 0. 01 ）. Using multivariate logistic regression analyses, an increase in NT-proBNP level after CABG was found to be independently associated with AF （ OR = 3.78, 95% IC = 1.81 - 4. 89, P 〈 0. 01 ）. Increased age, diabetes mellitus, preoperative use of β-blocker, proximal right coronary artery involvement, and longer operation time were al- so associated with AF. Conclusions These results indicated that AF was associated with higher NT-proBNP concentrations after off pump CABG; the increase in NT-proBNP after CABG may play an important role in the occurrence of AF after the operation. The further studies are needed to define the reason that lead to higher NT-proBNP concentrations among the patients who present AF after off pump CABG.
