The prediction of the fragment velocity distribution of a cylindrical cased charge with end caps is one of the key issues to assess the damage efficiency of the warhead. However, limited work has been conducted to pre...The prediction of the fragment velocity distribution of a cylindrical cased charge with end caps is one of the key issues to assess the damage efficiency of the warhead. However, limited work has been conducted to predict the fragment velocity distributions along the axis of cylindrical cased charges with end caps. This paper presents a study of the velocity distribution of fragments caused by the explosion of a cylindrical cased charge with end caps. The fragment velocity distribution and the end cap velocity were determined by an X-ray radiography method, and the axial fragment distribution was determined by witness plates. It was found that the velocities of fragments, especially near the edge, were increased when the end caps were added, and the position of maximum velocity is closer to the non-detonation end. The fragment velocities were increased, and the fragment projection range was decreased with the increase of the thickness of the end cap. A formula for fragment velocity distributions of a cylindrical cased charge with end caps, which is based on Huang’s formula, was proposed by the theoretical analysis and data fitting and validated experimentally. The results indicate that the proposed formula is accurate in predicting the fragment velocity distribution along the axis of a cylindrical cased charge with end caps detonated at one end.展开更多
An anhydride monomer containing ether oxide bridge, 7-oxa-bicyclo[2,2,1]hept-5-ene-2,3-dicarboxylic anhydride （ONA）, was successfully synthesized by Diels-Alder reaction of furan and maleic anhydride. The ONA was al...An anhydride monomer containing ether oxide bridge, 7-oxa-bicyclo[2,2,1]hept-5-ene-2,3-dicarboxylic anhydride （ONA）, was successfully synthesized by Diels-Alder reaction of furan and maleic anhydride. The ONA was also studied as an end-cap for the polymerization of monomer reactant （PMR） type polyimides. Three molecular weight levels of the ONA end-capped PMR resins were evaluated. The effects of process conditions of these novel PMR resins on thermal and mechanical properties were investigated. It was demonstrated that the imidized prepolymers using the end-cap have good processability, and the cured polyimide specimens exhibited good thermal stability. The initial decomposition temperature, Td （ca. 580℃） and glass transition temperature, Tg （330℃） of the novel resin （PI-20）, prepared trader optimum process conditions, compare favorably with the Td （ca. 620℃） and Tg （ca. 348℃） of the state-of-the-art resin （PI＇-20）, respectively.展开更多
Fluoro-terminated hyperbranched（poly（aryl） ether ketone）（HPOP-PEEK-F） with 4-phenoxyphenyl side groups was prepared from A2（2-（4-phenoxyphenyl）-1,4-diphenol） and B3（1,3,5-tris[4-（4-flourobenzoyl） phenoxy]...Fluoro-terminated hyperbranched（poly（aryl） ether ketone）（HPOP-PEEK-F） with 4-phenoxyphenyl side groups was prepared from A2（2-（4-phenoxyphenyl）-1,4-diphenol） and B3（1,3,5-tris[4-（4-flourobenzoyl） phenoxy]benzene） with a function group ratio of 0.48:1（A2:B3）.The chemical structure of HPOP-PEEK-F was confirmed by FTIR and（）1H-NMR.The degree of branching（DB） of HPOP-PEEK-F was 0.66 determined by（）1H-NMR measurements.The phenyl ethynyl-terminated hyperbranched poly（ether ether ketone）（HPOP-PEEK-PEP） was prepared by the end-capping approach.The HPOP-PEEK-PEP showed high glass transition temperature than HPOP-PEEK-F,but exhibited lower thermal stability.After cross-linking,the glass transition temperature,thermal stability and anti-chemical corrodibility of HPOP-PEEK-PEP were all improved.展开更多
C\-\{60\}\|end\|bonded polystryrenes(PS\|C\-\{60\}\|Br) with narrow molecular weight polydispersity were prepared by atom transfer radical polymerization (ATRP) in good yield.GPC results show that the polydispersities...C\-\{60\}\|end\|bonded polystryrenes(PS\|C\-\{60\}\|Br) with narrow molecular weight polydispersity were prepared by atom transfer radical polymerization (ATRP) in good yield.GPC results show that the polydispersities of these fullerene polymeric derivatives were between 1.1 and 1.3.The brown color of the solution indicates that C\-\{60\} has been bonded into the polymer,which was confirm by UV\|vis.Furthermore,2\|amino\|acetonictrile was used as an IR label to react with PS\|C\-\{60\}\|Br,and the product show the characteristic absorption of CN group at 2369cm\+\{-1\}.These results reinforce the conclusion that C\-\{60\} has been covalently bonded into the polymer.A possible mechanism of the formation of C\-\{60\}\|end\|bonded PSt was deduced tentatively.展开更多
Five samples of perfluoroheptyl end capped polyacrylic acid ( F P A A) having ahigh surface activity were prepared by free radicalpolymerization ofacrylicacid . Theinitiatorwas perfluorooctanoyl peroxide which produce...Five samples of perfluoroheptyl end capped polyacrylic acid ( F P A A) having ahigh surface activity were prepared by free radicalpolymerization ofacrylicacid . Theinitiatorwas perfluorooctanoyl peroxide which produced the free radicalof heptyl at 45 ℃. The yieldsof F P A A were in the range of 10 % to 25 % . The weight average molecular weights were2 62 ×104 to 7 99 ×104 and the polydispersity indexes were 1 97 to 5 64 ,depending on theconcentration of the initiator in the monomer. The surface tension was about 15m N/m at30 ℃forthe aqueous solution of F P A Awith the weight average molecular weight2 62 ×104in the concentration of about 0 01g/ m L. The molecular areas of F P A A at the air waterinterface under the condition ofcritical micelle concentration were 3 2 to 4 6n m2 ,which areobviously larger than the area per molecule of perfluorooctanoic acid (2 14nm 2) and muchsmaller than that of ordinary polyacrylic acid (83 4nm 2) . It means that the polymermoleculesin the surface adsorbed layer form the brush structure because of the special effectof the perfluoroalkyl groups at the chain ends .展开更多
基金financial support from the exploratory project of State Key Laboratory of Explosion Science and Technology, China (No. QNKT19-09)。
文摘The prediction of the fragment velocity distribution of a cylindrical cased charge with end caps is one of the key issues to assess the damage efficiency of the warhead. However, limited work has been conducted to predict the fragment velocity distributions along the axis of cylindrical cased charges with end caps. This paper presents a study of the velocity distribution of fragments caused by the explosion of a cylindrical cased charge with end caps. The fragment velocity distribution and the end cap velocity were determined by an X-ray radiography method, and the axial fragment distribution was determined by witness plates. It was found that the velocities of fragments, especially near the edge, were increased when the end caps were added, and the position of maximum velocity is closer to the non-detonation end. The fragment velocities were increased, and the fragment projection range was decreased with the increase of the thickness of the end cap. A formula for fragment velocity distributions of a cylindrical cased charge with end caps, which is based on Huang’s formula, was proposed by the theoretical analysis and data fitting and validated experimentally. The results indicate that the proposed formula is accurate in predicting the fragment velocity distribution along the axis of a cylindrical cased charge with end caps detonated at one end.
基金financially supported by the Research Foundation of State Key Laboratory of Applied Organic Chemistry
文摘An anhydride monomer containing ether oxide bridge, 7-oxa-bicyclo[2,2,1]hept-5-ene-2,3-dicarboxylic anhydride （ONA）, was successfully synthesized by Diels-Alder reaction of furan and maleic anhydride. The ONA was also studied as an end-cap for the polymerization of monomer reactant （PMR） type polyimides. Three molecular weight levels of the ONA end-capped PMR resins were evaluated. The effects of process conditions of these novel PMR resins on thermal and mechanical properties were investigated. It was demonstrated that the imidized prepolymers using the end-cap have good processability, and the cured polyimide specimens exhibited good thermal stability. The initial decomposition temperature, Td （ca. 580℃） and glass transition temperature, Tg （330℃） of the novel resin （PI-20）, prepared trader optimum process conditions, compare favorably with the Td （ca. 620℃） and Tg （ca. 348℃） of the state-of-the-art resin （PI＇-20）, respectively.
文摘Fluoro-terminated hyperbranched（poly（aryl） ether ketone）（HPOP-PEEK-F） with 4-phenoxyphenyl side groups was prepared from A2（2-（4-phenoxyphenyl）-1,4-diphenol） and B3（1,3,5-tris[4-（4-flourobenzoyl） phenoxy]benzene） with a function group ratio of 0.48:1（A2:B3）.The chemical structure of HPOP-PEEK-F was confirmed by FTIR and（）1H-NMR.The degree of branching（DB） of HPOP-PEEK-F was 0.66 determined by（）1H-NMR measurements.The phenyl ethynyl-terminated hyperbranched poly（ether ether ketone）（HPOP-PEEK-PEP） was prepared by the end-capping approach.The HPOP-PEEK-PEP showed high glass transition temperature than HPOP-PEEK-F,but exhibited lower thermal stability.After cross-linking,the glass transition temperature,thermal stability and anti-chemical corrodibility of HPOP-PEEK-PEP were all improved.
文摘C\-\{60\}\|end\|bonded polystryrenes(PS\|C\-\{60\}\|Br) with narrow molecular weight polydispersity were prepared by atom transfer radical polymerization (ATRP) in good yield.GPC results show that the polydispersities of these fullerene polymeric derivatives were between 1.1 and 1.3.The brown color of the solution indicates that C\-\{60\} has been bonded into the polymer,which was confirm by UV\|vis.Furthermore,2\|amino\|acetonictrile was used as an IR label to react with PS\|C\-\{60\}\|Br,and the product show the characteristic absorption of CN group at 2369cm\+\{-1\}.These results reinforce the conclusion that C\-\{60\} has been covalently bonded into the polymer.A possible mechanism of the formation of C\-\{60\}\|end\|bonded PSt was deduced tentatively.
文摘Five samples of perfluoroheptyl end capped polyacrylic acid ( F P A A) having ahigh surface activity were prepared by free radicalpolymerization ofacrylicacid . Theinitiatorwas perfluorooctanoyl peroxide which produced the free radicalof heptyl at 45 ℃. The yieldsof F P A A were in the range of 10 % to 25 % . The weight average molecular weights were2 62 ×104 to 7 99 ×104 and the polydispersity indexes were 1 97 to 5 64 ,depending on theconcentration of the initiator in the monomer. The surface tension was about 15m N/m at30 ℃forthe aqueous solution of F P A Awith the weight average molecular weight2 62 ×104in the concentration of about 0 01g/ m L. The molecular areas of F P A A at the air waterinterface under the condition ofcritical micelle concentration were 3 2 to 4 6n m2 ,which areobviously larger than the area per molecule of perfluorooctanoic acid (2 14nm 2) and muchsmaller than that of ordinary polyacrylic acid (83 4nm 2) . It means that the polymermoleculesin the surface adsorbed layer form the brush structure because of the special effectof the perfluoroalkyl groups at the chain ends .
