Thermo-chemical decomposition of RDX in cyclohexanone and gamma-butyrolactone

摘要

To improve its crystalline quality, RDX is processed in suitable solvents, among them are cyclohexanone and gamma-butyrolactone. In spite of its relatively high thermal stability, RDX can decompose to a certain extend during processing. Several qualities of RDX were investigated: so-called insensitive RDX (I-RDX) from Eurenco, Sorgue, France and so-called sensitivity reduced RDX (RS-RDX) from Chemring, Saetre, Norway. With ARC™ (Accelerating Rate Calorimetry) solutions of 8 mass-% RDX in the two solvents have been used with I inch titanium ARC™ bombs. The ARC from THT Inc. was operated in the so-called 'heat-wait-search' mode to register the decomposition exotherm followed by pseudo-adiabatic selfheating. The temperature range of detected decomposition is between 130°C and 230°C. The amount of RDX was used-up during the course of the decomposition, means after the end of selfheating all RDX was consumed. The curves show an initial faster increase in self-heat rate. Mostly this is indicative for chemical species, which accelerate decomposition. Such features can be caused autocatalytically or by impurities. The curves were described with reaction kinetic models and Arrhenius parameters have been obtained. The isothermal heat flow microcalorimetry (I-HFMC) measurements were performed with TAM™ III and a modified TAM™ II instruments from TA Instruments. Isothermal measurement temperatures were between 80°C and I30°C.The data evaluation was done by differential iso-conversional description. To have an indication about the amount of RDX decomposition in the HFMC runs, additional solutions were aged and analysed with HPLC. The curve shapes of heat flow curve (dQ/dt) and integrated heat flow indicate self-accelerating decomposition as well as the course of RDX decrease obtained by direct analysis. Finally, some thoughts about reaction pathways are communicated.