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A process has been devised to deposit graphite on to the surface of RD1355 (monobasic lead azotetrazole) using a combination of wetting and nonionic flocculating agents. The product is homogenous, but it is not suitable for use as a conducting composition. The resistance of the pressed compositions are very sensitive to variations in graphite content compared with the equivalent compositions made by the dry mix process.

The interactions of nitroglycerine in double-base propellants with the inhibition materials cellulose acetate and ethyl cellulose are described. The distribution of nitroglycerine within the inhibitor and the effects of time, temperature, nitrocellulose content of the propellant, barrier layers and fillers on rates of absorption are covered. Reference is made to methods of bonding ethyl cellulose to propellant. The investigations are extended to a range of polymers which are possible inhibitors, and also to a number of plasticizers likely to be present.

The behaviour of composite and double-base propellant rocket motors on storage is reviewed and the problems of safety and deterioration in performance are considered with emphasis on the basic chemical and physical changes involved. Storage at elevated temperatures is shown to be very important and accelerated testing is used to predict the effects of much longer cool storage. Tests necessary to avoid eventual spontaneous inflammation include compatibility of ingredients and materials, temperatures of ignition, estimation of the rate of stabiliser consumption and its relation to the safe chemical life, and measurement of heat evolution to permit calculation of cook-off limitations on charge dimensions for double-base or similar reactive propellants.

Opportunity was taken at Exercise WESTMINISTER to make recordings of sonic bang waveforms for use as standards of comparison by which the explosively generated simulant waveform under development at ERDE could be judged. A variation of the sonic bang waveform along the aircraft track, first reported in the USA, was observed in this country for the first time. From the recorded waveforms, energy spectra and loudness values were computed, corresponding to the median and extreme forms of the variation. It is concluded that (1) the subjective effects of sonic bangs can vary markedly with the location of the observer along the aircraft track, even though the flight conditions and local topography are constant, and (2) the ERDE Mark I explosive simulant is very suitable for the assessment of the effects of sonic bangs on building structures.

Modification of the crystal habit of urea by crystallization from water in the presence of additives, and from a wide range of organic solvents was investigated. Addition compounds of urea with alicyclic ketones, hitherto unreported, were discovered. The favorable physical properties of these addition compounds were found to make them suitable intermediates in the preparation of urea in a free-flowing, non-caking form. The parameters for the laboratory manufacture of this type of urea were examined as a basis for a large-scale continuous process. An investigation into the possible use of this type of urea as a host for the selective absorption of certain organic solvents was made.

The reactions of the azotetrazole (5,5'-azoditetrazole) anion with dilute nitric, sulphuric, hydrochloric, phosphoric, perchloric, acetic, carbonic acids and acidic ceric ammonium nitrate have been investigated. The degradation of the azotetrazole anion by dilute hydrochloric and dilute sulphuric acids has been confirmed to give 5-hydrazinotetrazole as proposed by Thiele. However other high nitrogen products have also been isolated; one of which is explosive. With dilute nitric acid the degradation gave, as well as gaseous products, 5- azidotetrazole whose salts, especially that of silver, are hypersensitive to mechanical stimulus.

The pyrolysis of a range of organic lead compounds used as ballistic modifiers has been studied using thermogravimetry and differential thermal analysis. The results show that the lead compounds of aliphatic carboxylic acids decompose to lead oxide in one stage which, in air, is largely oxidative in character. The compounds of the aromatic hydroxy acids, however, first yield intermediate basic compounds of varying stability and these ultimately decompose to lead oxide at high temperatures. When heated in nitrogen dioxide vapour the lead compounds react with the gas but the products so formed from the aromatic series were found to ignite below 150 deg C. on further heating in nitrogen dioxide. Differential thermal analysis showed that in these latter cases the initial reaction involving the uptake of NO(2) is exothermal and that this effect can be detected if a propellant containing the lead salt is treated with excess nitrogen dioxide at an elevated temperature.

The kinetics of the thermal decomposition of 2-ethyldecaborane have been investigated for a static system in the temperature range 210 deg - 230 deg C and at 2-ethyldecaborane pressures of 100 - 600 mm Hg. The decomposition leads initially to decaborane and diethyldecaboranes, its rate is of the second order with respect to 2-ethyldecaborane; the activation energy is 39.5 +/- 0.5 koal/mole. In the later stages of the decomposition the reaction deviates from the second order dependence due to side reactions which give nonvolatile solid hydrides, alkylated nonvolatile solid hydrides, hydrogen, methane and a little ethane. 1,2-diethyldecaborane is always present in the products in greater concentration than 2,4-diethyldecaborane. This and other results have been interpreted in terms of a hyperconjugation effect of the alkyl group with the a B-B bonds in the decaborane structure.

An assessment has been made of the use of the metals Li, Be, B, Mg, Al alone, in suspension in a hydrocarbon, and as hydrides, with the oxidant Nitric Acid. The best performance is obtained with systems based on Be and B, but the increase in performance, compared with a hydrocarbon fuel, is not sufficient to warrant a great deal of research on these fuels, particularly for medium size motors (approx 5000 lbs. thrust). Some objections to the use of metals, even for lower performance systems, are discussed.

The specific gravity, viscosity, sensitiveness, calometric value, and refractive index of nitroglycerine, triacetin, and mixtures of these, with and without carbamite, have been determined. Details of methods and results are recorded.

Guanidine nitrate may be prepared by reacting nitrolim with a concentrated aqueous solution of ammonium nitrate at temperatures between 120 deg and 160 deg C., the so-called Direct Fusion', Process. A pilot plant has been installed and operated on this process at Waltham Abbey. It comprises a continuous reactor operating at 120 deg C. and ancillary plant to isolate the product and concentrate and recycle excess ammonium nitrate liquor. Successful operation has been achieved in several runs of about 200 hours continuous duration and outputs up to 50 lb. per hour of guanidine nitrate have been obtained. An isolated yield of 87% calculated on the calcium cyanamide content of the nitrolim has been obtained with a reaction time of 1 hour and the yield is expected to rise to over 90% by allowing greater reaction time. The product purity has averaged 98% guanidine nitrate. A comparison with plant which would be necessary for batch operation shows that the principal advantage of the continuous process lies in a simpler operating procedure and reduced labour requirements. Preliminary plant flowsheets for producing 50 short tons/week of guanidine nitrate have been prepared (Figs. 1, 2, 3, 4) and the dimensions of the principal plant items calculated and tabulated. These are based on an estimated 95% conversion of calcium cyanamide to guanidine nitrate and an ammonium nitrate consumption of 110% of theory.

A machine for assessing the friction sensitiveness of explosives and propellants has been designed to operate at velocities up to 30 ft/s (10 m/s), with a maximum dead load of 300 lb (150 kg). This has been accomplished by allowing the peripheral face of a metal disc to act on a flat metal plate, the load being applied pneumatically. The motion of the disc is effected by means of a flywheel striking a movable latch. The prototype machine has successfully completed its initial tests. Load and velocity can be varied simply, and the time taken to perform the tests is less than with the modified pendulum machine upon which the action is based. Further proving trials will be needed before the use of the machine can be recommended as a standard test procedure.

Measurements of the burning-surface temperatures of fuel-weak ammonium perchlorate/paraformaldehyde mixtures have been made up to pressures of 300 psia, using an infrared emission technique. Temperature determinations up to 60 psia were reasonably reproducible, the values being compatible with the existence, at the surface, of an equilibrium between solid ammonium perchlorate and the gaseous decomposition products, NH3 and HC1O4. Results above 60 psia were rather erratic, and failure to eliminate the variations by experiment led to an examination of the natural limitations of the optical method for measuring the surface temperatures of fast-burning compositions. The temperature gradients within the solid became too steep even for this method, which can 'see' as little as 2 microns of surface depth., Presented at International Symposium on Combustion (10th), The Combustion Institute, p1373-80 1965.

Ten fully compounded rubber stocks representative of natural and synthetic rubber mixes have been stored for periods up to twelve months and their processing and cure characteristics determined. Results show that after storage at room temperature, satisfactory mouldings may be produced from most of the stored stocks, both by injection and compression moulding, having similar properties to those produced from unstored materials. Ten fully compounded stocks, five of natural and five of synthetic rubber, have been stored at room temperature and 40C for various times and vulcanisates prepared from them by compression and injection moulding have been subsequently aged at 80C for up to 16 weeks. The general ageing characteristics of the vulcanisates prepared from the stocks are not altered to any significant degree by storage, provided that each stock is given its optimum cure., See also Part 1, AD0741904.

Two propellants (a cast double-base and an extruded double-base) and two explosives (a 60/40 RDX/TNT mixture + 1% beeswax and nitromethane) were subjected to shocks of known amplitude. The shock producing system used was essentially that of the NOL Standard Gap Test. Threshold pressures for both burning and detonation were obtained. This technique (used originally by Jacobs and Liddiard) has been extended to provide unreacted Hugoniot data.

The 1H spectra of twenty-one nitrate esters have been measured. These were the higher alkyl nitrates, from n-propyl to n-decyl nitrate, as well as iso-propyl and iso-butyl nitrates; ethylene, tri-, tetra-, and pentamethylene dinitrates; 2,2'-oxydiethyl dinitrate (diethylene glycol dinitrate); glycerol 1,3-dinitrate; 2-chlorotrimethylene dinitrate; meso-1,2-dimethylethylene dinitrate; and glycerol 1,2,3- and butane 1,2,4-triyl trinitrates. A complete analysis of the spectrum was not possible for any of the compounds: a number, like the corresponding fluorides, give deceptively simple spectra. In others the resolution is not sufficient to allow all the NMR parameters to be evaluated. A brief discussion of the parameters which were obtained, and their use in the analysis of mixtures is given., Paper copy also available from Mintech, TIL, Block 'A', Station Square, St. Mary Cray, Orpington, Kent. BR5-3RE.

Current experimental studies, at E.R.D.E. and elsewhere, on various aspects of the combustion of ammonium perchlorate-based propellants are discussed in relation to an accepted model for composite propellant burning. The nature of the chemical processes taking place at the solid/gas interface and the possibility of heat release in the condensed phase are considered. A summary of the results of surface temperature measurements on ammonium perchlorate burning under a variety of conditions from 0.8 to 300 p.s.i.a. is presented. Although the evidence is that some heat release is likely to occur within the solid surface, the combustion in all pressure regions appears to be dominated by gas phase reactions. Results with catalysts which are supposed to increase the extent of the condensed phase reaction do not alter this conclusion.

The explosives compatibility properties of a number of commercial epoxy resin materials are discussed and reported and an account is given of hazard appraisal and compatibility tests of several reactive hardener components and of resin-hardener mixtures in the uncured condition.

The electrical capacitances of a number of subjects wearing insulating or conductive types of footwear on various insulating or conductive floors have been measured. The values range from 150 - 300 micromicrofarads for insulated conditions to 700 - 1500 micromicrofarads for conducting conditions. The effective skin resistances during electrostatic discharges from the hands and finger tips have been determined; also several measurements have been made under low-voltage continuous-current conditions. The values of resistance determined by the dynamic method are considerably smaller than those given by the low-voltage method. The results of the capacitance and resistance measurements are discussed in relation to the electrostatic hazard of handling primary explosives, and to a possible circuit equivalent to a discharging person.

The effects of variations in test procedure have been examined and a standard method of testing and interpretation is proposed using the Silvered Vessel test propellant (F527/327) as substrate. A preliminary investigation into the use of other propellant compositions as substrate is described.

A technique for the determination of the sensitiveness to shock of liquid explosives in moderate bulk (on the order of 100 ml) has been developed. This is giving reliable results with explosives which are less sensitive than ethyl nitrate and more sensitive than propyl nitrate.

The reaction between nitrogen dioxide and colloidal propellant stabilisers is exothermic, and an apparatus based on the heat of the nitrogen dioxide-propellant reaction is used in Holland for surveillance control of gun propellants. A similar apparatus has been constructed and the heat of this reaction compared in propellants stabilised with carbamite, diphenylamine, picrite, 2-NDPA, p-NMA and resorcinol. The observed heat from the nitrogen dioxide-aged propellant reaction, and the actual stabiliser content of the samples, are compared as these propellants are aged.

A review has been made of the results of tests on cast double-base propellants containing para-nitro-N-methylaniline (NMA) as a stabiliser. The review is based on 80 deg C Silvered Vessel (SV) tests and stabiliser consumption trials carried out at both ICI and ERDE. The available evidence shows that NMA is adequate as a replacement for 2-nitrodiphenylamine (NDPA) for some uses although not as good in ultimate stabilising power. An initial 1% minimum of NMA may be suitable as sole stabiliser in conventional double-base propellants but slightly more may be required for unfavourable compositions or where a Service Chemical Life much in excess of 10 years at 32 deg C is required. It is found that composite modified compositions require resorcinol in addition to NMA for adequate chemical stability. Clarification is needed of Land Service requirements to enable the required figures for Service Chemical Life to be specified.

The method for determination of resorcinol which is based on spectrophotometric measurement of copper nitrosoresorcinate has been modified to improve its sensitivity and reliability.

A form of silver 5-nitrotetrazole has been developed which can be filled into small devices. It has been tested, together with mercuric 5- nitrotetrazole, for detonant and stab-sensitive properties. Both compositions have been shown to be stable and will efficiently detonate RDX in large detonators but neither, in their current physical form, are technically suitable for current UK design of small detonators. The silver salt dead presses at loads too low for adequate consolidation; the mercuric salt detonates the RDX but not as efficiently as lead azide. Neither salt is stab-sensitive. Recommendations are made concerning the future synthetic and crystal modification programmes, methods of assessment, and potential application of these compounds., See also Part 2, AD727350.

With a view to a more rigorous application of scientific principles to the problem of premature detonation of RDX/TNT fillings in shell, recent experiments on ignition and propagation in secondary explosives are briefly described. These lead to certain conclusions which need to be taken into account in formulating an acceptable mechanism for shell prematures. As a result, it seems that ignition of the filling is an insufficient cause for detonation except in circumstances where pressures substantially in excess of the yield- strength of the shell wall can also be generated, for instance by impulsive loading as in an impact. Some indications of the scope for future experimental studies are mentioned briefly.

A new process has been developed for the manufacture of styphnic acid (2,4,6-trinitroresorcinol). Resorcinol is treated with dilute nitric acid and sodium nitrite to give 2,4-dinitrosoresorcinol, and the latter is pumped as a slurry into hot concentrated nitric acid, in which it undergoes oxidation and nitration to yield styphnic acid (90 per cent). The process has been evaluated in collaboration with ROF, Bridgwater, and appears to be more convenient and economical than the conventional sulphonation/nitration method.

The detection and identification of traces of explosives by means of colorimetric spot tests performed upon an adhesive tape substrate have been examined. The adhesive tape serves as a very effective means of collecting a sample, either from suspect material, a working surface, or from the skin of a suspect. Nineteen explosives were examined, these being chosen as representative of military, commercial and amateur explosives. Nineteen different tests were examined, and with the exception of ammonium perchlorate all the explosives considered were found to give a positive response to some, but not all tests. A scheme of analysis was devised that would separate all the candidate explosives. While the investigation has greatly increased the number of spot tests known to be suitable for colorimetric reactions on an adhesive tape substrate, consideration has shown that a multiplicity of tests is not necessarily suitable for use by non-scientists for field testing. Limited, but adequate identification of most explosives may be obtained using only two of the tests. In the course of the investigation a new colorimetric test for RDX and HMX was discovered, and one for perchlorates; in addition, the suitability of an existing test for cyanides for the detection of nitroaromatics was exploited.

Small scale experiments using silica gel, ammonium nitrate and urea show that formation of guanidine nitrate becomes erratic if insolubles build up on the catalyst surface. The rate of production of insolubles increases rapidly with temperature, so that a trade-off between low conversions at lower temperatures and insoluble formation at higher temperatures is possible. The yield/temperature relationship is a property of the silica gel used. Yields of guanidine nitrate can be higher than predicted, possibly because by-product water is removed in the form of ammonium silicates rather than ammonium carbamate. Experiments with N15 and 018 suggest that guanidine nitrate does not result from the direct combination of cyanamide and urea: oxygen (or hydroxyl groups) of the silica gel plays an important role. The rate of formation of guanidine nitrate is second order (first order in both urea and ammonium nitrate). The phase diagram for the ternary system has been investigated.

Over the temperature range examined (350 to 475 deg C) polyether-polyurethane rubbers gasify more readily than polyisobutene which, in turn, gasifies at a faster rate than polyester-polyurethane rubbers. Prepolymers gasify at a slower rate than the corresponding polyurethane rubbers. At 350 deg C all of the polymers examined give first order reactions but increasing the temperature to 475 deg C produces deviation from first order behavior. There is evidence that at the higher temperatures free-radical breakdown is responsible for the rapid rate of gas production. Polyisobutene gives a high monomer yield at lower temperatures but at 475 deg C methane and ethylene are also formed. The polyurethane rubbers produce acetaldehyde, methane, ethylene, and carbon monoxide; the polyethers, in addition, give propylene and the polyesters carbon dioxide. Not all of the polymer pyrolysed can be accounted for by these simple gases; the other products probably consist of a mixture of higher molecular weight hydrocarbons.

In a case-bonded rocket motor the propellant is often subjected to biaxial tensile straining, arising from thermal or pressurisation effects. The behaviour of propellants under biaxial straining differs from that under uniaxial straining, and special biaxial test techniques have to be devised. Plastic propellants have some biaxial characteristics in common with other types of propellant, and other which are peculiar to this type of propellant. An account is given of the way in which biaxial strains arise in certain types of plastic propellant motor, and of the testing techniques. They include spin testing, diaphragm testing and a development of the standard crack test. The effects of time, temperature, age hardening and asymmetry on biaxial properties were investigated. An account is given of the application of biaxial test results to design problems of the Bantam motor for the Skua meteorological rocket, and to the development of propellants for this application.

Measurements of the amount of choke erosion in a two-inch solid propellant motor containing approximately 3/4 lb. of aluminised polyurethane propellant have been made, using as choke materials a wide range of commercial grades of graphite and a limited number of processed grades of graphite. The erosion of metal chokes made from tungsten, molybdenum, and tantalum was also measured. Under the conditions of these tests it was found that of the graphites investigated, Nobrac grade M3/HF had the highest resistance to erosion. Tungsten was the only metal tested that was superior to the best grades of graphite. The throat erosion of expansion nozzles using the same type of motor was also investigated. In this case the study was restricted to nozzles made from four materials, viz. one commercial grade of graphite, a silicon with a propellant containing 5% aluminum the copper-base alloy, Hidurel 6 proved superior to the other materials tested. All the materials tested eroded substantially when fired with propellants containing 20% aluminium.

This memorandum summarises existing information concerning the effect of composition on the tendency of large charges of plastic propellant to deform, or slump under their own weight. Studies of the current type of formulation have indicated that further improvements in slump resistance are possible as the result of changes in solids content, particle size, or binder viscosity. Brief investigations of the use of polymerisably polyester plasticisers and a modified 'plastisol' process have given encouraging results. These and other means of modifying the binder will be further investigated. Present evidence suggests that an increase in tensile strength of 100 to 200% is feasible, but this may be accompanied by some loss of extensibility.

An account is given of a 150 ml bomb calorimeter developed in ERDE and installed in Government propellant factories and Service Inspectorate laboratories for quality control and inspection in double-base propellant manufacture. The preparation of a standard SC (Cordite) propellant and the measurement of its calorimetric value, using the combustion of benzoic acid in oxygen in a stainless steel bomb as standardising reaction, and the determination of the energy equivalent of the calorimeter with normal high-tensile steel bombs using this standard SC propellant are described.

A description is given of work which has enabled the Williams-Landel- Ferry (WLF) method of time temperature superpositioning of tensile test data to be applied to the routine assessment of experimental plastic propellant compositions. The report is in two parts. The first part deals with experimental improvements which have recently been made particularly with regard to the estimation of the effective gauge length; a comparison of the procedure with the American (ICRPG) standard method is included. The second part deals with the computerization of the calculations performed on tensile data. This has enabled the time required to carry out a WLF analysis to be reduced from one week to about one day., Paper copy also available from Technology Reports Centre, Station Square House, St. Mary Cray, Opington, Kent, England. BR5 3RE.

Contents: Rocket Motors and Explosives--Solid rocket propellants, Chemical engineering, and High Explosives, Initiators and their Ingredients.

Environmental testing problems are considered, primarily from the standpoint of the propellant chemist. Environments are defined and the significant aspects of motor design and possible failure modes considered. Preliminary tests, and environmental tests proper, which aim to simulate storage, transport and handling hazards in a realistic manner, are discussed, together with the size and scope of a test program. In conclusion the importance of surveillance is emphasized, in order that the results of these programs can be checked and adequate reasons established to account for any failures.

The use of data-logging and data-processing techniques for the calculation of the results of tensile tests on polymers is described. It is shown that values obtained in this way do not differ significantly from those obtained by conventional means, and result in a considerable saving in time and effort. In addition, the results are consistently reproducible, and use of a data logger can give better recording accuracy than does a chart recorder.

The many factors influencing the choice of suitable sealing methods for ammunition and allied stores are summarized. The importance of adequate waterproofing is emphasized, in view of the widely varying atmospheric and other conditions to which stores in Service are liable to be subjected. The properties required in sealing compositions are outlined and performance specifications for lutings and cements are proposed. Details of selected lutings and cements are given on individual data sheets. The types of joint normally used are considered, and the methods of applying sealing compositions to them are discussed. A bibliography with abstracts of 24 references is included., Supersedes Rept. no. ERDE XR 350/13.

Work has been carried out at ERDE on double-base propellants containing lead beta-resorcylate and basic cupric salicylate to which carbon blacks have been added. For most of the work the standard solventless process was used; the fastest platonised burning rates were obtained with a carbon black, and one formulation, F488/1827, burning at 41 mm/s at pressures between 17 and 34 MN/sq m has been the subject for development trials. At lower calorimetric values, slower burning rates were obtained, but platonisation could be extended to pressures of at least 45 MN/sq m or to 51 MN/sq m by changing to low nitrogen content nitrocellulose. Replacement of some nitrodiphenylamine by resorcinol gave further increases in burning rate. Attempts to increase burning rates by activation of the carbon black and charcoal were not successful and similar burning rates were obtained with somewhat larger amounts of untreated carbon black. Solvent processed versions of some promising fast burning formulations for use in thin web sizes were satisfactorily tested.

A method of determining the burning surface temperatures of solid propellant compositions by measurement of the infrared emission from the surface is described. Specific wavelengths, at which the solid emission is high and the gas emission is low, were selected for the measurements. Very weak fuel/NH4ClO4 powder mixtures, burning at atmospheric pressure, have a constant surface temperature of 495 !15 C irrespective of the burning rate. Practical propellant compositions, containing rather more than stoichiometric proportions of fuel with NH4ClO4, give a similar temperature provided that the hot gas emission can be successfully eliminated, but interference from the gas leads to maximum measured temperatures of about 560 C. The average surface temperature of a double-base propellant increases with burning rate; temperatures range from 300 to 400 C at atmospheric pressure. Binder fuels currently used in composite propellants also have surface temperatures close to 500 C when burning in a diffusion flame with oxygen.

The preparation and properties of three polymorphic modifications of monobasic lead trinitroresorcinate have been studied. By varying the method of preparation, and by the employment of small quantities of additives, a range of products of different physical form and properties, including reduced sensitiveness to spark ignition, can be obtained. Two such products have possible technical applications for electrical initiation and explosive priming and delay purposes. They have been developed to the manufacturing scale. Compared with normal lead trinitroresorcinate the new varieties offer improved chemical and thermal stability combined with promising explosive characteristics.

The mechanical relaxation stiffness of two grades of polytetrafluoroethylene (PTFE) are compared using the ERDE stress relaxation test. The materials are an unfilled PTFE and a filled PTFE. For short loading times the filled PTFE is found to be the stiffer material, but in the long term the unfilled PTFE has a better performance.