赤磷基发烟剂的热分解及稳定性研究.pdf

doi10． 3969／ j． issn． 1001- 8352． 2018． 04． 001 Thermal Decomposition and Stability of Red Phosphorus Smoke Agent with Different Oxidants * SHAN Congming， LIU Jie， ZHU Shunguan， ZHANG Lin School of Chemical Engineering，Nanjing University of Science and Technology （ Jiangsu Nanjing， 210094） ［ABSTRACT］ Thermal behaviors of red phosphorus （RP） and its mixtures with oxidants， such as KNO3， Ba（NO3）2， MnO2， Fe2O3， and KMnO4， were studied experimentally using differential thermal analysis （DTA） and thermogravimetry （TG） s in air atmosphere． Oxidation temperature of RP and decomposition temperatures of oxidants mentioned above were obtained．For the KNO3＋ RP ＋ Teflon， Ba（NO3）2＋ RP ＋ Teflon， MnO2＋RP ＋ Teflon， Fe2O3＋ RP ＋ Teflon， and KMnO4＋ RP ＋ Teflon pyrotechnic systems， chemical reaction happen within the range of 399． 5- 469． 8 ℃， 445． 7- 471． 6 ℃， 409． 8- 479． 3 ℃， 419． 8- 466． 5 ℃ and 396． 2- 467． 4 ℃， respectively．Self- accelerating decomposition temperature （Te0）， critical ignition temperature （Tb）， apparent activation energy （E），△S ＃， △H＃， and△G＃of the pyrotechnic mix- tures were measured according to DTA- TG experiments．Furthermore， friction sensitivity and property of hygroscopicity of pyrotechnic mixtures were examined．Based on these data， appropriate oxidants in red phosphorus smoke agent，which are Ba（NO3）2， MnO2and Fe2O3，can be selected． ［KEYWORDS］ red phosphorus smoke agent； ignition temperature； kinetic parameters； red phosphorus ［CLASSIFICATION CODE］ TQ567 赤磷基发烟剂的热分解及稳定性研究 单聪明 刘 杰 朱顺官 张 琳 南京理工大学化工学院（江苏南京，210094） ［摘 要］ 采用热重- 差热（TG- DTA）分析方法在空气气氛中对赤磷（RP）、硝酸钾 KNO3、硝酸钡 Ba（NO3）2、二氧 化锰 MnO2、氧化铁 Fe2O3、高锰酸钾 KMnO4及其混合物的热分解行为进行研究。 所得结果如下赤磷与 KNO3、 Ba（NO3）2、MnO2、Fe2O3、 KMnO4构成混合物的反应温度区间分别为 399． 5 ～ 469． 8 ℃、445． 7 ～ 471． 6 ℃、409． 8 ～ 479． 3 ℃、419． 8 ～ 466． 5 ℃、396． 2 ～ 467． 4 ℃。 同时，根据不同升温速率下赤磷与不同氧化剂组成的混合物的热分 析结果，计算得到各混合物的自加速分解温度（Te0），临界点火温度（Tb）、活化能（E）、活化熵（△S ＃）、活化焓 （△H ＃）以及活化吉布斯自由能（△G＃）等重要参数。 另外，对赤磷与不同氧化剂组成混合物的摩擦感度和吸湿性 也进行了研究，根据这些结果发现最适合与赤磷组配的氧化剂为 Ba（NO3）2、MnO2和 Fe2O3。 ［关键词］ 赤磷发烟剂；点火温度；动力学参数；赤磷 Introduction As an important ingredient for the manufacture of pyrotechnic smokes， red phosphorus （RP） has been widely used in screening applications where obscuration is achieved in various portions of the electromagnetic spectrum， including the visible range and in several IR bands．It is likely to be in service for many years ［1］ ． In spite of the extensive use of pyrotechnic smokes， delays， signals， incendiaries， only in the last two decades some attentions have been paid to under- stand and apply the laws of thermodynamics and the principles of solid state chemistry to explain the vaga- ries of pyrotechnic systems ［2- 3］ ．Recent investigations into the parameters affecting the pyrotechnic reactions 第47 卷 第 4 期 爆 破 器 材 Vol． 47 No． 4 2018 年8 月 Explosive Materials Aug． 2018 * 收稿日期2018- 01- 24 作者简介单聪明（1988 - ），男，硕士，主要从事火工药剂的性能研究。 E- mail13097363230163． com 通信作者朱顺官（1962 - ），男，研究员，主要从事火工药剂技术和新型爆破器材研究。 E- mailzhusgmial． njust． edu． cn 万方数据 showed that the complicated chemical behavior of these reactions in solid state could be attributed to various factors， including the nature of oxidants and fuels， particle size， impurities， and oxidation layers on the surface of fuels ［4- 6］ ．However， there is a need for de- velopment of appropriate models to take these parame- ters into account． However， the thermal stability of RP- based pyro- technic mixtures is less reported， and also the ua- tion s．In this paper， differential thermal analy- sis （ DTA） coupled with thermogravimetry （ TG） were used to analysis the reaction process and uate the stability of pyrothchnic mixture．Thermal analysis is a well- established technique for studying the thermochemical and thermophysical properties of ener- getic materials in reasonable way ［7- 8］ ． This can reveal the relation between ignition temperature and thermal behavior， which governs the safety of a pyro- technic mixture ．Such thermal analysis s are useful for substances exhibiting exothermic or endother- mic changes when temperature is varied ［9- 11］ ．Such studies of pyrotechnic compositions are important not only for understanding the kinetics of their thermal de- composition， but also for assessing the effect of their exothermic decomposition and ignition temperature on potential hazards during handling， usage， and storage． Therefore，to provide ination on the sensitivity of igniter compositions to various accidental factors． In this paper， the thermal behavior and ignition temperature of the following pyrotechnic mixtures were measured KNO3＋RP ＋Teflon， Ba（NO3）2＋RP ＋ Teflon， MnO2＋RP ＋Teflon， Fe2O3＋RP ＋Teflon， and KMnO4＋RP ＋Teflon．Non- isothermal kinetic analysis was used to estimate Arrhenius parameters of the combustion reactions ［12］ ．This study was focused on the thermoanalytical properties of the individual re- actants and the binary pyrotechnic mixtures．Their thermal behavior has been compared for future applica- tions as conventional pyrotechnic mixtures． Furthermore， friction sensitivity and hygroscopici- ty of pyrotechnic mixtures， which are important factors to uate the stability of pyrotechnic mixtures， were measured．The three parameters （ ignition tempera- ture， friction sensitivity and hygroscopicity） are the most important factors for the pyrotechnic mixtures to uate the potential hazards during handling， usage， and it storage．And it has the guiding siginificance for the practical application． 1 Experiment 1． 1 Materials Red phosphorus powder with a particle size of about 80- 100 mesh was provided by Shanghai Zhanyun Chemical Co． ， Ltd． （China）．KNO3， Ba（NO3）2and Fe2O3werepurchasedfromSinopharmChemical Reagent Co． ， Ltd．with particle size of 120 mesh． MnO2（120 mesh） was provided by Shantou Xilong Chemical Factory．KMnO4（120 mesh） was purchased from Shanghai Lingfeng Chemical Reagent Co． ， Ltd． Teflon with a particle size of 5 μ m was purchased from Shanghai 3F New Materials Co． ， Ltd．All of them were of analytic reagent grade． 1． 2 Procedure 1． 2． 1 Preparation of the ternary mixtures All chemicals were stored in a vacuum oven at 60 ℃ before being mixed．The ternary mixtures （oxidi- zer／ combustibles／ binders） which the total mass of the compositions were 3 g were initially prepared by wet mixing in acetone based on the ratio presented in Tab． 1．After evaporation of the solvent， small quantities of the pyrotechnic mixtures were carefully sieved through a sieve slightly coarser than the particles． 1． 2． 2 Thermal analysis of the samples A thermal analysis instrument of HCT- 2 was used for TG／ DTA studies．Pure compounds and mixtures were separately studied under similar conditions （the heating rate and sample s weight were 10 ℃／ min and 2． 0 mg， respectively） using TG／ DTA thermal analysis instrument in air atmosphere．Thermochemical beha- vior of pure RP， KNO3， Ba（NO3）2， MnO2， Fe2O3， KMnO4and mixtures of them were characterized ac- cording to Tab． 1．The mixtures had the same oxygen balance （OB -90 g oxygen／ 100 g sample） except KMnO4＋ RP ＋ Teflon pyrotechnic mixture （OB - 108 g oxygen／ 100 g sample）， because it is easy to be igni- ted．The mass fraction of KMnO4is 12％， which is much less than the others ．DTA experiments were run at the heating rates of 10， 12， 14， and 16 ℃／ min from 25 ℃ to 700 ℃ with sample s weight of 2． 0 mg 2 爆 破 器 材 第 47 卷第 4 期 万方数据 Tab． 1 Summary of experimental results for DTA／ TG of pure components and mixtures No．Components Mass fraction／ ％ Transition temperature a） ／ ℃ Fusion b） Ignition or decompositionT * 1 ＃ RP100▌364*． 3364． 3- 423． 3（increase） 2 ＃ KNO3 100▌336 ． 8500*． 05003． 0- 800． 0（decrease） 3 ＃ Ba（NO3）2 e100▌598 ． 0594*． 25943． 2- 695． 1（decrease） 4 ＃ MnO2 100▌548 ． 3537*． 05373． 0- 560． 9（decrease） 5 ＃ Fe2O3 100▌1 565． 0 6 ＃ KMnO4 100▌224*． 32243． 3- 298． 0（decrease） 7 ＃ KNO3＋ RP ＋ Teflon20w． 0，77． 0，3． 0354 ． 3331． 2，399． 5 3313． 2- 378． 3（decrease） 399． 5- 469． 8（increase） 8 ＃ Ba（NO3）2＋ RP ＋ Teflon21w． 5，75． 5，3． 0445*． 7445． 7- 471． 6（increase） 9 ＃ MnO2＋ RP ＋ Teflon20w． 5，76． 5，3． 0409*． 8409． 8- 479． 3（increase） 10 ＃ Fe2O3＋ RP ＋ Teflon22w． 1，74． 9，3． 0419*． 8419． 8- 466． 5（increase） 11 ＃ KMnO4＋ RP ＋ Teflon12w． 0，85． 0，3． 0200． 0，396． 0 2003． 0- 350． 0（decrease） 396． 2- 467． 4（increase） a）Peak temperatures at maximum heat flux． b） Fusion temperatures for the mixtures are given for fuel and oxidants， respectively．T * is temperature range associated with a variation of samples weight． in air atmosphere．All the samples were dried before testing， and the measurements were repeated three times． 1． 2． 3 Test for friction sensitivity The combine falling angle swing hammer was used to measure the friction sensitivity of the pyro- technic mixtures． There were six different falling angles， 90 ， 80 ， 70 ， 60 ， 50 ，and 40 ， respec- tively and the corresponding to the pressures were 4． 50， 3． 50， 2． 80， 2． 10， 1． 50 MPa， and 1． 00 MPa．Each combination needed to be tested 20 times． The equation of average ignition ratio was★Pi＝ ni／ 20 100％， and the cumulative ignition ratio was P ＝ ∑n／ 120 100％ ． 1． 2． 4 Test of hygroscopicity Five grams RP or pyrotechnic mixtures were placed in a thermo- hygrostatic chamber kept at a con- stant temperature of 25 ℃ and a relative humidity of 95％．The resulting test sample was weighed to calcu- late the percentage of increasing weight after 7 days． Relative hygroscopic rate （％） ＝hygroscopic rate of pyrotechnic mixture／ hygroscopic rate of RP 100％． 2 Results and discussion 2． 1 Thermal properties of pure compounds Fig． 1 （a） shows TG and DTA curves for pure compounds． Pure RP powder shows a sharp exothermic peak in 411． 6 ℃．At this temperature， the compound reacts with oxygen and TG curves shows considerable increasinginthesampleweight（ approximately 109． 5％ in the experimental value and 103． 2％ in the theoretical value） in temperature range between 364． 3- 423． 3 ℃ because of the produced P2O3and P2O5． 4P（s） ＋ 4O2（g）P2O3（s） ＋ P2O5（s）。 Fig． 1（b） shows the TG／ DTA curves of KNO3 sample used in this study．In alignment with recent re- ports by Koch ［13］ and Freeman ［14］ ， the endothermic peaks at 139． 5 ℃ and 336． 8 ℃ correspond to phase transition of rhombic crystalline solid to trigonal struc- ture and melting of KNO3， respectively．The molten KNO3is stable up to 500 ℃ and then decomposition reaction starts at above this temperature， and finishes at about 1 000 ℃， resulting in no solid residue ［15］ ． The result of theoretical mass loss is 53． 5％， and the experimental mass loss is 30． 2％ because of incom- plete reaction． 4KNO3（l）2K2O（l） ＋ 6NO（g） ＋ 3O2（g）。 Thermal analysis （DTA／ TG） of pure Ba（NO3）2 indicats that the melting of Ba（NO3）2with a strong en- dothermic peak at 598． 0 ℃ ［Tab． 1 and Fig． 1（c）］， which subsequently decomposed at 652． 0 ℃．After complete decomposition of the sample， oxygen， nitrous oxide and barium oxide are produced ［16］ 3 Thermal Decomposition and Stability of Red Phosphorus Smoke Agent with Different Oxidants 2018 年8 月 SHAN Congming，et al 万方数据 Fig． 1 TG and DTA curves 2Ba（NO3）2（s） 2BaO（s） ＋ 4NO（g） ＋ 3O2（g）。 As shown in Fig． 1（d）， an endothermic peak at 548． 3 ℃ is observed， corresponding to decomposition of MnO2．The TG curve confirms this result by decrea- sing 8． 7％ weight of sample． After complete decompo- sition of the sample， O2and MnO are produced 2MnO2（s）2MnO（s） ＋ O2（g）。 As shown in Fig． 1（e）， an endothermic peak at 240 ℃ is observed， corresponding to decomposition of KMnO4．The TG curve confirms this result by decrea- sing 98． 85％ weight of sample．After complete decom- position of the sample， O2， K2O and MnO2are pro- duced 4KMnO4（s） 4MnO2（g） ＋ 2K2O（g） ＋ 3O2（g）。 2． 2 Thermal properties of mixtures DTA and TG curves of RP and KNO3mixture are shown in Fig． 2（a）．The DTA curve reveals a weak exothermic peak at 354． 3 ℃ with about 3． 0％ mass loss， which is the decomposition of KNO3．Up to the decomposition point the DTA curve reveals two exother- mic peaks at 436． 5℃ and 466． 0℃ with about 92． 6％ mass increase． This is due to the oxidation of RP． And the exothermic peak at 436． 5 ℃ is corresponds to the pre- oxidation of RP． As the heating rate increased， the two exothermic peaks combined into an exothermic peak．According to the decomposition reaction equa- tion of KNO3and the mass gain （92． 6％） of the sam- ple， the complex solid state reaction could be represen- ted as follows 34P（s） ＋ 10KNO3（s） ＋ 23O2（g） 5K2O（s） ＋ 5P2O5（s） ＋ 12P2O3（s） ＋ 10NO（g）。 Fig． 2（b） shows the DTA and TG curves for the sample containing RP and Ba（NO3）2．A sharp exo- thermic phenomenon was observed at 471． 2 ℃ with about 102． 4％ mass increase， which is corresponding to the oxidation of RP by nitrate and air．According to the decomposition reaction equation of Ba（NO3）2and the mass gain （102． 4％） of the sample， the following reaction equation could represent the complex solid state reaction． 84P（s） ＋ 20Ba（NO3）2（s） ＋ 53O2（g） 20BaO（s） ＋ 20P2O5（s） ＋ 22P2O3（s） ＋ 40NO（g）。 Fig． 2（c） shows DTA and TG curves for the mix- ture of RP and MnO2．There are two exothermic peaks （436． 3 ℃ and 476． 1 ℃） in the DTA curve with about 111． 0％ mass increase， which is due to the oxi- dation of RP．The weak exothermic peak at 436． 3 ℃ may be the pre- oxidation of RP．As the heating rates increased， the two exothermic peaks combined into an exothermic peak， which can be demonstrated by Fig． 3 （e）．According to the decomposition reaction equation of MnO2and the mass gain （111． 0％） of the sample， the reaction is as follows 12P（s） ＋ 4MnO2（s） ＋ 11O2（g） 4 爆 破 器 材 第 47 卷第 4 期 万方数据 Fig． 2 TG and DTA curves for mixtures 4P2O5（s） ＋ 2P2O3（s） ＋ 4MnO（s）。 Fig． 2（d） shows DTA and TG curves for the mix- ture of RP and Fe2O3．DTA curve of RP／ Fe2O3mix- ture shows a sharp exothermic peak around 461． 5 ℃ with 98． 9％ mass increase due to oxidation of RP． The temperature of exothermic peak for the mixture of RP and Fe2O3is higher than the neat RP， which is due to the Fe2O3makes the oxidation rate of RP slows down． The melting point of Fe2O3is 1 565 ℃， which is so high that the Fe2O3is solid state when the RP is oxi- dized．And the RP is surrounded by the solid state Fe2O3which slow down the oxidation reaction．Accor- ding to the mass gain （98． 9％） of the mixture， the reaction equation is as follows 24P（s） ＋ 23O2（g）5P2O5（s） ＋ 7P2O3（s）。 Fig． 2（e） shows the DTA and TG curves for the mixture of RP and KMnO4．In the TG curve， the weight loss （12． 4％） at 200- 360 ℃ with a slow slope that is corresponds to the releasing of oxygen during de- composition process of KMnO4．After decomposition， the mixtures undergo a sharp exothermic peak around 461． 8 ℃ with two week exothermic peaks 396． 2 ℃ and 444． 9 ℃．And the TG curve shows 80． 5％ mass increase with the temperature range 396． 2- 461． 8 ℃， which is due to the oxidation of the RP by the perman- ganate and air．According to the decomposition reac- tion e