硝化纤维素细断新工艺技术研究

为了解决我国目前的硝化纤维素细断（粉碎）过程能耗高、效率低、污染严重的问题,文章利用双圆盘粉碎机对硝化纤维素进行了细断试验。重点研究了粉碎时间、磨刀类型、磨刀间距及浆料浓度等因素对细断效果的影响,得出了合适的工艺条件。与传统锥形细断机相比,该技术与设备节能45％,提升了我国硝化纤维素细断工艺技术水平。     

Thermoreversible gelation of nitrocellulose solutions

Thermoreversible gelation of concentrated solutions of nitrocellulose was examined. The sol–gel transition diagrams were established using the ball‐drop method. The critical gel concentrations (C_gel), defined as the lowest concentration for gelation to occur, are approximately proportional to the reciprocal of the molecular weight of nitrocellulose. In addition, the values of C_gel[η] lie in the concentrated regime where entanglement effects are present. These facts suggest that the entanglement of polymer chains is a necessary condition for the formation of nitrocellulose gels. Moreover, the association of polymer segments is identified as another factor affecting the gel stability. This is evidenced by both the enhancement of the gel stability in poor solvents and the large enthalpy of mixing at low temperatures. Because of the presence of the association, the number of polymer chains in a junction point is larger than two, which is the value predicted by assuming entanglements as the only factor responsible for gelation. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 4000–4008, 2003     

Combustion-Front Non-One-Dimensionality in Single- and Double-Base Propellants

Parameters of transverse waves propagating over the surface of specimens pressed from colloxylin and double-base propellants A and N are studied. By means of microvideofilming and thermocouple measurements, it is shown that the burning sites on the specimen surface are formed by a set of transverse waves. Under atmospheric pressure, the transverse-wave front has the form of a step 0.5–1.1 mm high and decreases with increasing pressure or initial temperature of the specimen. The front propagates with variable velocities in the horizontal and vertical directions. The mean velocity of the transverse wave is three to eight times higher than the normal burning rate of the specimen as a whole (with a wide spread of local values) and increases with increasing pressure. Behind the front, combustion can be interrupted till the arrival of the next transverse wave. As in the SHS process, the reason for the emergence of the transverse waves is combustion-wave spatial instability.     

The sorption of iso-propyl nitrate and acetone into nitrocellulose/nitroglycerine films

Rates of sorption of iso-propyl nitrate and acetone vapour into nitrocellulose films plasticized with nitroglycerine have been measured. In all cases, although fractional uptakes were approximately proportional to the square root of time, they were also independent of film thickness. Such behaviour indicates a ‘Case III’ mechanism in which the film expands uniformly with no appreciable concentration gradients. A kinetic equation, which describes uptakes of up to 90% is suggested.     

精制棉成熟度及硝化工艺对高氮量NC硝化均匀性的影响

为研究精制棉质量、硝化工艺对高氮量硝化纤维素(NC)硝化均匀性的影响规律,采用H_2SO_4-HNO_3-H_2O体系对不同成熟度的精制棉进行硝化处理,通过改变硫酸-硝酸比、硝化时间制备了高氮量NC,利用偏光显微镜测试NC的含氮量及硝化均匀性,探讨了不同成熟度和硝化工艺对高氮量NC的氮量及硝化均匀性影响规律,同时将不同均匀性的NC经胶化压制成典型的发射药,对比了相应药粒侧断面的微观形貌。结果表明,精制棉成熟度高时,制备的高氮量NC均匀性优于成熟度低的产品;硫硝比为2.7时,制备的NC含氮量高、硝化均匀性较好;以成熟度大于70%的精制棉为原料,制备NC的硝化均匀性指标-均方差约2.3;30~35min硝化效果最佳,延长硝化时间对氮量影响不大,均匀性反而降低。表明,以成熟度高的精制棉为原料,通过控制硝化体系中硫硝比和硝化时间,可得到均匀性较好的NC,用其压制单基发射药的胶化和压伸成型质量可得到明显改善。     

硝基快干汽车修补漆的制备

通过试验,用1/2s硝酸纤维素溶液和热塑性丙烯酸树脂制备硝基快干汽车修补漆,讨论了二者比例、氨基树脂、增塑剂和有机溶剂等对涂料性能的影响。结果表明,当1/2s硝酸纤维素溶液和热塑性丙烯酸树脂比例为38∶39,丁基化三聚氰胺甲醛树脂添加量为4.5%,邻苯二甲酸二丁酯添加量为3%,有机溶剂选择恰当时,该硝基涂料的综合性能良好。     

DIANP对NC溶塑作用的实验与模拟

用动态流变实验和扫描电子显微镜观察对比研究了1,5-二叠氮-3-硝基氮杂戊烷(DIANP)和硝化甘油(NG)溶塑硝化纤维素(NC)的速率和效果,用分子动力学模拟方法对DIANP、NG、NC的溶度参数和DIANP、NG在NC中的扩散系数进行了模拟计算,采用介观动力学模拟方法得到了NC/DIANP和NC/NG共混体系的介观形貌。结果表明,与NG相比,DIANP溶塑NC速率较快,二者在NC中的扩散系数分别为1.39×10~(-10)m~2·s~(-1)和2.24×10~(-10)m~2·s~(-1)。相对于NG,DIANP溶塑效果更好,两种共混体系的显微形貌特征与介观动力学模拟结果具有很高的一致性。溶度参数计算结果表明,DIANP的分子间作用力大小与NC较为相似,而NG溶度参数的范德华力和静电力分量所占的比例与NC接近。     

AP/Al/CMDB推进剂表面和界面性能研究

采用动态接触角和界面张力仪研究了氮含量不同的硝化棉(NC)与不同粒度的高氯酸铵(AP)表面性能以及NC与填料之间的界面性能,研究了界面性能对含AP和铝粉(Al)改性双基推进剂(AP/Al/CMDB)力学性能的影响。结果表明,NC的氮含量越低,AP的粒度越小,它们的表面张力以及其极性分量和非极性分量愈大。同时AP的粒度越小,NC与AP间界面张力和粘附功越小;但由于界面张力减小的效应强于粘附功越小的效应,推进剂的抗拉强度仍增大。而NC氮含量愈小,NC与AP间界面张力越小、粘附功愈大,推进剂抗拉强度增强。     

竹浆纤维素纳米纤维对硝化纤维素膜的增强作用

为获得力学性能更好的硝化纤维素膜材料,对竹浆进行2,2,6,6-四甲基哌啶-1-氧基自由基(TEMPO)选择性催化氧化-超声处理,得到直径纳米级、长度微米级的纤维素纳米纤维(cellulose nanofibrils,CNFs)。采用N,N-二甲基甲酰胺(DMF)或DMF/H2O混合溶剂作分散剂,先后将硝化纤维素与酸化和未酸化的CNFs进行充分混合,在不同的分散剂条件下制备出CNFs增强的硝化纤维素膜,采用透射电镜(TEM)、热重(TG)、力学拉伸试验、动态力学热分析(DMTA)等测试表征了CNFs形态尺寸以及CNFs增强的硝化纤维素膜力学性能变化规律。结果表明,CNFs的直径为5～10 nm,长度为500～3000 nm;酸化与未酸化的CNFs在DMF中分散性均好于丙酮溶液;在DMF/H2O分散体系中水的体积分数达到20%时出现了CNFs团聚;在DMF分散剂体系中,加入酸化的CNFs制备出的复合膜拉伸强度为52.0 MPa,断裂伸长率为10.4%,显著高于空白样(36.6 MPa,8.4%)。     

Properties and Application of a Novel Type of Glycidyl Azide Polymer (GAP)‐Modified Nitrocellulose Powders

GAP‐modified nitrocellulose powders were prepared by an internal solution method and applied in cross‐linked modified double base (XLDB) propellants. It was found that GAP‐modified nitrocellulose powders exhibit high round, no bonding between the particles and excellent fluidity. When the amount of GAP increased from 10.0 % to 30.0 %, the median diameter (d₅₀) of powders decreased from 134.53 μm to 94.54 μm. The thermal decomposition process of GAP appeared also in the GAP‐modified nitrocellulose powders, but the thermal decomposition peak temperatures of  N₃ and the GAP main chain were found to be lower for the 10.0 % and 20.0 % GAP‐modified samples than the corresponding peak temperatures for pure GAP, respectively. The plasticizing properties of GAP‐modified nitrocellulose powders are better than that of pure nitrocellulose powders, and the drop weight impact sensitivity of the modified powders is reduced as the mass ratio of GAP increases. It was experimentally shown that GAP‐modified nitrocellulose powders can improve the mechanical characteristics of the propellant with a maximum tensile strength (σ_m) between 0.36 MPa<σ_m< 1.10 MPa and an elongation at maximum tensile strength (ε_m) between 28.8 %<ε_m<51.8 % at temperatures of −40, +20 and +50 °C.