CERES :: Browsing by Author "Gill, Philip P."

Browsing by Author "Gill, Philip P."

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Open Access
Chemical modification of β-cyclodextrins: balancing soft and rigid domains in complex structures
(Wiley, 2019-09-19) Luppi, Federico; Mai, Nathalie; Kister, Guillaume; Gill, Philip P.; Gaulter, Sally; Stennett, Christopher; Dossi, Eleftheria
Crystalline polymers such as β‐cyclodextrin (βCD) can be modified with polyethylene glycol (PEG) diglycidyl ether cross‐linkers (262, 394, 500 Da). Here we show that the quantity and length of the PEG soft segments influence the solubility and malleability of the products, which are water‐soluble and easily converted to nitrated analogues under standard reaction conditions. Inert and nitrated derivatives containing longer PEG segments showed the ability to self‐heal. The degree of cross‐linking and decomposition temperatures and energies depended on the quantity and length of the soft segment. Nitrated cross‐linked βCD containing longer PEG segments did not ignite following an electrostatic discharge of 4.5 J. The chemical stability of βCD/PEG binders was tested by heat flow calorimetry at 80 °C. We found that the balanced incorporation of soft PEG and rigid βCD segments improved the processability of cross‐linked βCDs and desensitised their nitrated derivatives, offering new solutions for inert and energetic binders.
Open Access
Determination and optimisation of Resonant Acoustic Mixing (RAM) efficiency in Polymer Bonded eXplosive (PBX) processing
(Elsevier, 2022-02-07) Claydon, Andrew J.; Patil, Ajay N.; Gaulter, Sally; Kister, Guillaume; Gill, Philip P.
An investigation into how the efficiency (time and energy required for homogeneity) of Resonant Acoustic Mixing (RAM) can be determined and optimised was undertaken. An idealised Polymer Bonded eXplosive (PBX) simulant based on glass microbeads (28.3 um D50, 62% v/v in binder and plasticiser) was used for mixing. Mixing evolution was monitored using machine output data, whereby the mixer ‘intensity’ (related to power draw) was plotted against time. Experiments were undertaken with three acceleration settings, three mixer units, and three vessel materials of low, medium, and high surface free energy. Different stages of the mixer ‘intensity’ profiles were found to correspond to discrete stages of mixing, as well as further rheological changes due to continued frictional heating, thus viscosity reduction, beyond homogeneity being achieved. Time to mixing completion was found to be repeatable within a standard deviation of +/- 10%, strongly dependent on acceleration setting, and additionally dependent on vessel material, though additional data is required to confirm this. A significant difference in mixing time was observed between different LabRAM units. Partial vacuum application without degassing was beneficial for mixing. Finally, a paradigm linking the ‘movement modes’ of mixing was constructed, based on literature observations and the experimental results.
Open Access
Evaluation of novel propellants manufactured from commercially available Thermoplastic Elastomers (TPE) using resonant acoustic mixing
(2019-06) Wilkinson, Peter John; Gill, Philip P.; Kister, G.
The key issues in developing a sustainable gun or rocket propellants are financial, environmental, legislative and safety. Use of commercially available off the shelf polymers, in particular, thermoplastic elastomers (TPE) as a binder for propellants could address these issues. The propellant would need to have suitable mechanical and thermal properties, as well as, adequate ballistic performance. Traditional manufacture techniques for propellant are not suitable for TPE binders and so new mixing and manufacturing techniques will be investigated. A literature review is presented detailing conventional propellants, low vulnerability (LOVA) propellants and research into using TPEs as binders for propellants. In addition, the desirable mechanical and ballistic properties of propellants are assessed. The TPEs PEBAX, a polyether-block-amide (PEBA) and SEBS, a Styreneethylene/butylene-styrene were selected for analysis. A full assessment of the mechanical and thermal properties of these TPEs was conducted. They both have broadly suitable properties, however, both TPEs were substantially stiffer (greater storage modulus) than a typical binder and the lower glass transition for SEBS was above the desired minimum operational temperature. When plasticised with Dioctyl Sebacate (DOS), both PEBAX and SEBS had a reduction in the storage modulus and lower glass transition. PEBAX did not show any noticeable effect on the upper (melt) transition, conversely SEBS showed a larger reduction in the upper (glass) transition. SEBS was down selected for further evaluation due to its better availability, purity and greater solubility in solvents. Traditional mixing and manufacturing techniques where not suitable for processing of propellants with TPE binders. Slurry processing (used in manufacture of pressed PBXs) was selected to coat the filler, creating a moulding powder. This was replicated with a novel method using resonant acoustic mixing (RAM). The moulding powder was then consolidated by remote hot pressing to simulate an industrial extrusion or rolling process. This process was used to successfully manufacture two propellants using SEBS as the binder, AP/SEBS containing ammonium perchlorate (AP) as a filler and RDX/SEBS with RDX. Inert fillers of sugar and talc were trialled, and mechanical testing of these inerts was found to be generally in good agreement with the live fills. ii Initial combustion work on RDX/SEBS by closed bomb analysis at low pressure was indicative of good burning, with a low burn rate. Both AP/SEBS and RDX/SEBS were subject to thermal and mechanical analysis. This showed that the glass transitions (Tg) were only slightly changed from pure SEBS. In comparison to AP-composite propellants, both the storage modulus (E’) from DMA and Young’s modulus (E0) from tensile testing were substantially greater. The maximum stress (σm) was similar, however the maximum extension (εb) was less. With further optimisation, such as use of bonding agents, plasticisers, optimised particle size and improve manufacturing methods, it is believed that the maximum extension could be increased. Therefore a SEBS based propellant should deform less to an applied force, but still have a similar extension and hence elasticity to hydroxyl-terminated polybutadiene (HTPB) composite propellants. These theoretical improved mechanical properties should result in a safer propellant. This research has increased the knowledge and understanding of propellants based on commercially available TPEs. It is anticipated that this will be valuable in developing sustainable propellants of the future.
Open Access
Evaluation of small-scale combustion of an insensitive high explosive formulation containing 3-nitro-1,2,4-triazol-5-one (NTO), 2,4-dinitroanisole (DNAN), and 1,3,5-trinitroperhydro-1,3,5-triazine (RDX)
(Taylor and Francis, 2020-05-25) Galante, Erick B. F.; Mai, Nathalie; Ladyman, Melissa K.; Gill, Philip P.; Temple, Tracey J.; Coulon, Frederic
Energetic materials are often disposed by open-burning or open-detonation as it is a cost-effective and efficient means of destroying explosive material, and often minimizes the need to transport hazardous explosives to treatment facilities. This practice is often scrutinized for the negative environmental impact of the odorous and unsightly toxic gaseous emissions as well as the resulting deposition residues, which often contain unburned energetic materials. With the increasing use of Insensitive High Explosive compositions in munitions, it is essential that the potential environmental impact of their disposal is assessed before their extensive use to prevent the kind of contamination incidents experienced with legacy explosives. Therefore, the aim of this work was to develop a controlled laboratory experiment to identify the gaseous emissions and the energetic material residues that are generated through the combustion of the IHE components 3-nitro-1,2,4-triazol-5-one (NTO), 2,4-dinitroanisole (DNAN), and 1,3,5-trinitroperhydro-1,3,5-triazine (RDX). A sealed vial containing small (mg) quantities of energetic material was heated until the energetic material combusted. Gas chromatography/mass spectrometry (GCMS) was used to calculate the oxygen consumption and to identify the gases that were generated. The solid residues were analyzed by high-performance liquid chromatography (HPLC) to quantify unburned energetic material. Results showed that DNAN was the most resistant to burning, thus leaving significant quantities of unreacted starting material in the vial. An interesting observation for the IHE formulation was that DNAN also inhibited the combustion of NTO and RDX. The gases emitted during the open burning of IHE components and mixtures included CO, CO2, and N2O as expected, but the proportions differed when the components and mixture were compared, reflecting the influence of DNAN on the burning behavior. From our data, we concluded that open-burning DNAN-based formulations is an environmentally unfavorable waste-management practice for the disposal of IHEs mainly due to generation of solid residues as well as unburnt DNAN.
Open Access
Influence of humidity on the decomposition process of double base rocket propellant
(Elsevier, 2023-09-29) Romero Jabalquinto, Alonso; Mai, Nathalie; Mohammed, Yahaya; Gill, Philip P.
The decomposition mechanisms of the polymer cellulose nitrate (NC) which is used in double base (DB) rocket propellants, have been extensively studied, and the influence of storage temperature on the lifetime of these energetic formulations is well known. However, the impact of humidity and water on the polymer decomposition process is poorly understood. This paper studies the influence of humidity on the decomposition chemistry of NC and its impact on shelf life. Stabiliser consumption was first analysed by ageing the propellant in sealed vials at different humidity levels for 7 days at an isothermal temperature of 90 °C. Samples were also analysed using heat flow calorimetry (HFC) at isothermal temperatures of 80 °C, 90 °C, and 100 °C. The results indicates that stabiliser depletion increases with increasing water content. Life assessment calculations (AOP 48 ed2) show that increasing the absolute humidity from 6 to 22 g m-3 will decrease the propellant life from 11 to 6 years (25 °C equivalents). The HFC results follow the same trend as the stabiliser depletion where greater absolute humidity increases the heat flow by up to 400 %. Unlike the pass/fail criteria for stabiliser depletion, the HFC samples passed the 10-year (25 °C equivalent) life criteria (STANAG 4582). A multi-temperature (80, 90, 100 °C) kinetic analysis of the initial heat flow showed that the heat flow rate increased with increasing humidity, but the activation energy for all humidity levels remained at 131 (± 3) kJ mol−1.
Open Access
Interaction and thermal studies on graphene oxide in NC/DEGDN/GO nanocomposites
(Royal Society of Chemistry, 2019-10-31) Yahya, Prima Kharisma Indra; Gill, Philip P.; Moniruzzaman, Mohammed
Before considering the uses of graphene oxide (GO) in nitrate ester-based materials for performance and safety improvement, its interaction, compatibility and dispersion with the host matrices need to be well understood. This work addresses the interaction and dispersity of GO with nitrocellulose (NC)/diethylene glycol dinitrate (DEGDN)-based nanocomposites. The GO and DEGDN were successfully synthesised and characterised. The NC/DEGDN proved to be a good hosting matrix for the dispersion of GO nanosheets. Analysis of atomic force microscopy (AFM) showed that the thicknesses of dispersed GO were in the range of 1–4 nm suggesting that the GO in the nanocomposite consists of 1–2 layers for a 0.5% w/w GO containing nanocomposite and 2–4 layers for a 0.75% w/w nanocomposite. ATR-FTIR spectroscopy analysis established red-shifting of 744 to 752 cm−1 for the O–NO2 bond stretching vibrations, indicating bond stabilization by donor electron from the GO. The Raman spectra analysis showed GO peaks blue-shifting and broadening which is attributed to hydrogen bonding interaction between GO sheets and –NO2 groups. The activation energy of nitrate ester decomposition of NC/DEGDN/GO nanocomposites increases as a function of GO content from 167 kJ mol−1 and reaches a maximum of 214 kJ mol−1 for a 0.5% w/w GO loading. This suggests an improvement of the nitrate ester bond stability. These findings open a new direction to the application of GO in nitrate ester-based materials for increased stability, safety and shelf life.
Open Access
Investigating the factors influencing RDX shock sensitivity
(2012-08-22) Hudson, R J; Gill, Philip P.
The shock sensitivity of RDX (cyclotrimethylenetrinitramine) is dependent upon factors including crystal size, morphology, internal defects, surface defects and HMX content. With the arrival of reduced sensitivity RDX (RSRDX) and the drive towards insensitive munitions (IM), understanding what influences sensitivity has become a significant topic within energetic materials research. During the RS-RDX international Round Robin Study (R4) the parameters which influence sensitivity were investigated, however large discrepancies were seen between different laboratories so the results were inconclusive. The objective of this work is to clarify how crystal properties and the manufacturing process affect RDX sensitivity. In this study the same RDX lots as those from the R4 were examined. Optical microscopy showed that internal defect content varied widely and was affected by the manufacturing process. A good correlation between sensitivity and defect quantity was seen for RDX lots produced by the same method. Likewise, microscopic examination also showed a large range of morphologies which was influenced by method of production. Scanning electron microscopy also showed that surface defects were approximately correlated to shock sensitivity, however general surface roughness agreed better with sensitivity than the number of specific defects such as cracks and holes. The mechanical properties of the RDX samples were investigated using nanoindentation. This showed a good correlation between the quantity of internal defects and modulus of elasticity, hardness and creep. There was also a good agreement between these parameters and sensitivity. Rheological analysis of RDX/polyethylene glycol suspensions indicated a good agreement between the rheological properties of the suspension and crystal morphology. This method could form a basis for a new testing method for RDX morphology. Differential scanning calorimetry demonstrated that crystal size influenced decomposition rate. The melting endotherm onset temperature and energy was correlated with HMX quantity.
Open Access
Investigation of environmental impacts on explosives by open burning
(2018-09) Galante, Erick Braga Ferrao; Temple, Tracey J.; Gill, Philip P.
New safety requirements are pressuring military organizations to replace TNT with insensitive high explosives (IHEs) containing DNAN, NTO and RDX but little is known about the behaviour IHE components and formulations in the environment. The environmental impact of ordnance during the in-service phase has been studied, but most reports concern TNT-based legacy explosives and their impact on soil rather than other environmental compartments. To address this knowledge gap, IHE samples ranging from milligrams in a closed system to grams and kilograms in an open system were tested in the laboratory and field, yielding environmental impact data that helps to determine the behaviour of the materials during open burning. The prediction software HYDRUS 1D was then fed with the empirical data and the actual and predicted outcomes for the behaviour of DNAN, NTO, RDX and the IHE formulation were compared to determine whether this software can be used to predict said impacts. The thermodynamic properties of DNAN make it more likely to melt, boil and sublimate during open burning, leaving ~70 % behind as unreacted residues. DNAN also inhibits the burning of RDX and NTO, such the near zero residual mass when these are burned as pure compounds increases to ~20 % of the initial mass when the formulation is burned. Overall, the experiments showed that DNAN-based IHEs behave in a similar manner to TNT-based legacy explosives regarding emission of greenhouse gases, but worse in terms of solid residues. Ultimately, the body of work reported through this thesis has shown that traditional open burning of DNAN-based IHE could leave as much as 12 % (w/w) of unburnt explosive on the soil. We have therefore concluded that the open burning methodology adopted for TNT-legacy munitions should be avoided for disposing of IHE explosives
Open Access
Is ResonantAcoustic Mixing® (RAM) a game changer for manufacturing solid composite rocket propellants?
(Wiley, 2021-10-07) Wright, Christopher J.; Wilkinson, Peter J.; Gaulter, Sally E.; Fossey, Donald; Burn, Andrew O.; Gill, Philip P.
This study is a structured literature review of published ResonantAcoustic® Mixing (RAM) literature, considering the benefits and constraints of using RAM. Focussing on how this will affect the future production of rubbery composite rocket propellants. The main benefits of RAM were found to be shorter mixing time, versatility of mixing and ability to mix higher viscosities than conventional mixers. Facilitating the next generation of composite propellants with improved performance and mechanical properties. Mixed in-situ RAM overcomes viscosity limitations by removing the casting process and has safety and environmental benefits, but does need to be tested at larger production scales. The implications of RAM production on the energetics qualification process was considered. A new framework was discussed based on understanding the entire product development process including ingredient properties, manufacturing processes, and linking this to product performance; through adoption of a digital twin approach with in-situ monitoring. Future R&D focuses on process and material control through a validated model of the mixing mechanisms, linked to material properties and output performance. Validation with scaled up comparative studies and continuous in-situ monitoring. A full list is provided in the conclusions. Overall RAM offers numerous benefits to mixing existing and new materials with large savings in time, cost, improved safety and is more environmentally friendly.
Open Access
Modified Arrhenius kinetics for double base propellant decomposition: effect of water
(Elsevier, 2024-05-31) Romero Jabalquinto, Alonso; Mai, Nathalie; Belghiche, Samira; Gill, Philip P.
Numerous studies have been conducted on the decomposition mechanisms of cellulose nitrate (NC), a polymer employed in double base (DB) rocket propellants. It is well known that storage temperature affects the lifetime of these energetic formulations. However, less studies have been published on the influence of water. This research examined the role of water on the stabiliser consumption rate during accelerated ageing of a DB rocket propellant, as well as the impact on the shelf life prediction of the energetic formulation. Different volumes of water (0.8, 1.6, 2 and 4 µl/g) were added to the propellant in sealed vials, which were then isothermally aged (70, 80, 90, 100 °C). Analyses of the stabiliser consumption showed a faster decomposition kinetics in presence of water which is indirectly linked to the shortening of the storage life of the NC based propellant by 35 %. For the conditions, an activation energy of 133 ± 4 kJ/mol was reported for the water catalytic decomposition mechanism. A numerical model that included water as a variable was reported to reduce the uncertainty in the determination of the service life of NC based propellant. International standards such as Allied Ordnance Publication 48 should not overlook the effect of water/moisture on the safety of ammunition containing NC and should implement a modified Arrhenius equation.
Open Access
Morphological variations of explosive residue particles and implications for understanding detonation mechanisms
(2016-08-23) Abdul-Karim, Nadia; Blackman, Christopher S.; Gill, Philip P.; Morgan, Ruth M.; Matjacic, Lidija; Webb, Roger; Ng, Wing H.
The possibility of recovering undetonated explosive residues following detonation events is well-known; however, the morphology and chemical identity of these condensed phase postblast particles remains undetermined. An understanding of the postblast explosive particle morphology would provide vital information during forensic examinations, allowing rapid initial indication of the explosive material to be microscopically determined prior to any chemical analyses and thereby saving time and resources at the crucial stage of an investigation. In this study, condensed phase particles collected from around the detonations of aluminized ammonium nitrate and RDX-based explosive charges were collected in a novel manner utilizing SEM stubs. By incorporating the use of a focused ion beam during analysis, for the first time it is possible to determine that such particles have characteristic shapes, sizes, and internal structures depending on the explosive and the distance from the detonation at which the particles are recovered. Spheroidal particles (10–210 μm) with microsurface features recovered following inorganic charge detonations were dissimilar to the irregularly shaped particles (5–100 μm) recovered following organic charge firings. Confirmatory analysis to conclude that the particles were indeed explosive included HPLC-MS, Raman spectroscopy, and mega-electron volt–secondary ionization mass spectrometry. These results may impact not only forensic investigations but also the theoretical constructs that govern detonation theory by indicating the potential mechanisms by which these particles survive and how they vary between the different explosive types.
Open Access
Optical sensitisation of energetic crystals with gold nanoparticles for laser ignition
(Elsevier, 2017-05-18) Fang, Xiao; Sharma, Mishminder; Stennett, Christopher; Gill, Philip P.
The laser ignition of explosives is safer and more environmentally beneficial than electric ignition systems, but optical sensitisers must be present to facilitate heating by optical absorption. We investigated, for the first time, the optical sensitisation of cyclotrimethylenetrinitramine (RDX) crystals by doping them with gold nanoparticles to enhance laser ignitibility using a near-infrared diode laser. RDX crystals physically coated with gold nanoparticles or recrystallised from a solution containing gold nanoparticles were tested for optical sensitisation by micro-imaging with a scanning electron microscope, and high-speed video was used to experimentally observe the enhanced laser ignitibility. The gold nanoparticles achieved effective optical sensitisation and significantly enhanced the laser ignitibility of RDX, reducing the laser ignition threshold power from more than 45 W to as little as 1 W. Our results show that gold nanoparticles are effective as optical sensitisers for the ignition of energetic materials using a small, low-power diode laser.
Open Access
Post-blast explosive residue - a review of formation and dispersion theories and experimental research
(Royal Society of Chemistry, 2014-10-17) Abdul-Karim, Nadia; Blackman, C. S.; Gill, Philip P.; Wingstedt, M. M.; Reif, B. A. P.
The presence of undetonated explosive residues following high order detonations is not uncommon, however the mechanism of their formation, or survival, is unknown. The existence of these residues impacts on various scenarios, for example their detection at a bomb scene allows for the identification of the explosive charge used, whilst their persistence during industrial explosions can affect the safety and environmental remediation efforts at these sites. This review article outlines the theoretical constructs regarding the formation of explosive residues during detonation and their subsequent dispersal and deposition in the surrounding media. This includes the chemical and physical aspects of detonation and how they could allow for undetonated particles to remain. The experimental and computational research conducted to date is discussed and compared to the theory in order to provide a holistic review of the phenomenon
Open Access
Resonant acoustic mixing of polymer bonded explosives
(2021-01) Claydon, Andrew J.; Gill, Philip P.; Kister, Guillaume; Gaulter, Sally; Flood, Nathan
Current Polymer Bonded Explosive (PBX) formulation is limited by a compromise - optimised final properties against processability. While solid loading (explosive content) would ideally be maximised and plasticiser content would ideally be minimised, this would make the formulation too viscous to cast into its casing and require long and arduous mixing processes using conventional techniques. However, with Resonant Acoustic Mixing (RAM), PBX formulation does not have to be constrained. Instead of traditional mixing blades, mixing is achieved by the use of a vibrating platform to impart acoustic pressure waves (vibrations) into the mixture, agitating it. The added ability to mix in the end use casing (mixing ‘in-situ’) also renders casting obsolete in many scenarios. In order to maximise the benefits of RAM with regards to next generation formulation-optimised PBX manufacture (‘PBneXt’), the underlying mechanisms of how the technique works, how efficiency (time and energy required for homogeneity) can be determined and maximised, and how final material properties may change between casting and ‘in-situ’ processing methods, must be better understood. The research aim of the PhD is therefore to assess how mixing efficiency of RAM can be measured and optimised to maximise its benefits, with a focus on how aspects of machine control and mixing vessel design can be altered to improve the mixing mechanisms on which the technique relies. Areas investigated experimentally include the effects of acceleration and mixer intensity (linked to power draw) setting, mixer model and unit, vessel material (with regards to surface free energy and thermal properties), and vessel surface finish (with regards to roughness). It is found that by modifying these variables, the time and energy required for mixing can be substantially reduced. A comparison between material properties of composites mixed ‘in-situ’ and ‘mixed and cast’ is also undertaken. The findings are then reconciled with wider literature observations and recommendations are made as how to best implement RAM for ‘PBneXt’ manufacture, ultimately allowing for explosive compositions with improved performance, mechanical, safety, and ageing properties.
Open Access
The spatial distribution patterns of condensed phase post-blast explosive residues formed during detonation
(Elsevier, 2016-05-06) Abdul-Karim, Nadia; Blackman, Christopher S.; Gill, Philip P.; Karu, Kersti
The continued usage of explosive devices, as well as the ever growing threat of ‘dirty’ bombs necessitates a comprehensive understanding of particle dispersal during detonation events in order to develop effectual methods for targeting explosive and/or additive remediation efforts. Herein, the distribution of explosive analytes from controlled detonations of aluminised ammonium nitrate and an RDX-based explosive composition were established by systematically sampling sites positioned around each firing. This is the first experimental study to produce evidence that the post-blast residue mass can distribute according to an approximate inverse-square law model, while also demonstrating for the first time that distribution trends can vary depending on individual analytes. Furthermore, by incorporating blast-wave overpressure measurements, high-speed imaging for fireball volume recordings, and monitoring of environmental conditions, it was determined that the principle factor affecting all analyte dispersals was the wind direction, with other factors affecting specific analytes to varying degrees. The dispersal mechanism for explosive residue is primarily the smoke cloud, a finding which in itself has wider impacts on the environment and fundamental detonation theory.
Open Access
Styrene-ethylene/butylene-styrene (SEBS) block copolymer binder for solid propellants
(Wiley, 2021-09-20) Wilkinson, Peter J.; Weaver, Matthew C.; Kister, Guillaume; Gill, Philip P.
Currently solid composite propellants are manufactured using bespoke, specially manufactured binders. This adds significant cost and obsolescence risks to their development and manufacture. This paper reports on the production of two composite propellants made from a commercially-available-off-the-self polymer as binder by means of a resonant acoustic mixer (RAM) slurry process. The binder consisted of thermoplastic elastomer styrene-ethylene/butylene-styrene (SEBS) block copolymer and the solid filler, either ammonium perchlorate (AP) or 1,3,5-Trinitro-1,3,5-triazinane (RDX). Thermodynamic code demonstrated that SEBS-based propellants exhibited similar theoretical ballistic performance to conventional HTPB-based propellants. Chemical compatibility between SEBS and the solid fillers was shown by the differential scanning calorimetry (DSC) and vacuum stability methods. The novel combination of RAM and slurry coating process produced a propellant moulding powder that was then consolidated by remote hot pressing to simulate an industrial extrusion or rolling process. The propellants exhibited as expected explosive hazard properties and their thermal analysis by DSC-TGA showed typical oxidizer behaviour between AP and SEBS, characterised by two decomposition exotherms (also reported in AP/HTPB compositions), and little or no interaction between RDX and SEBS. The apparent activation energy for decomposition for AP/SEBS (84/16 % w/w) propellant was similar to that for AP/HTPB propellants. This work demonstrates the viability of using SEBS polymer as a binder for solid propellants. The development of propellants using commercially off the shelf, thermoplastic elastomeric binders could add significant benefits in waste reduction through recycling, security of supply, and manufacturing costs.
Open Access
The UK Ministry of Defence Project Orientated Environmental Management System (POEMS)
(Wiley, 2016-10) Ladyman, Melissa K.; Temple, Tracey J.; Gill, Philip P.; Galante, E.
The Project Orientated Environmental Management System (POEMS) is the UK Ministry of Defence (MoD) bespoke environmental management system for the acquisition and use of equipment. The full implementation of a site-specific environmental management system is challenging for the MoD because there are many permanent MoD sites with transient populations, frequently changing site activities and diverse types of equipment. Nevertheless, MoD policy requires that all sites are covered by an environmental management system. POEMS is based on international standards ISO14001 and ISO14040, which focus on environmental management systems and life cycle assessment, respectively. The primary aim of POEMS is to identify and manage any environmental aspects (causes) and impacts (effects) by scrutinising MoD equipment and activities during acquisition, operation and disposal. This is achieved by drawing up a priority list of activities associated with the equipment based on anticipated environmental impact scores, resulting in an environmental management plan that spans the life cycle of the equipment and any corresponding activities. This article describes the POEMS procedure for both experts and non-experts, and demonstrates the implementation of POEMS using a 105-mm artillery round as a theoretical case study. The results anticipated at each stage of the POEMS procedure are discussed in detail, and the documentation necessary to verify the correct application of POEMS is demonstrated.
Open Access
Ultrasonic studies of solid azobenzene decorated polymer thin films
(American Chemical Society, 2018-12-19) Moniruzzaman, Mohammed; Christogianni, Paraskevi; Vrcelj, Ranko; Gill, Philip P.
This work investigates the effect of ultrasound on switching of cis azobenzene isomers to their trans counterparts in solid films of methyl methacrylate and methacryloyloxyazobenzene copolymers [P(MMA/MOAB)]. UV/Vis and 1H NMR spectroscopy demonstrates that 46% of the cis isomer converts to the trans form purely by ultrasonic agitation and 46% converts to the trans isomer by localised ultrasound induced heating effects. Comparative studies of isomerisation by ultrasound wave, heat and visible irradiation shows that ultrasound exposure requires a longer time to switch the cis to trans conformation. The estimated activation energy for the cis to trans conversion in the solid polymer films is shown to be comparable to previous values of azobenzene isomerization, indicating that incorporation of the chromophore in a polymeric system affects the kinetics of transition, but not the barriers to conformational change.
Open Access
A whole life assessment of extruded double base propellants
(2013-09-25) Tucker, J; Gill, Philip P.
The manufacturing process for solventless extruded double base propellants involves a number of rolling and reworking stages. Throughout these processes a decrease in weight average molecular weight was observed, this was attributed to denitration. Differential scanning calorimetery data indicated that the reworking stages of extruded double base propellant manufacture were crucial to the homogenisation of the propellant mixture. To determine the homogeneity of the final extruded product, a sample was analysed across its diameter. No variations in stabiliser concentration, molecular weight, or Vickers hardness were detected. An accelerated thermal ageing trial simulating up to 8 years of ageing at 25°C was carried out to evaluate the storage characteristics. Reductions in stabiliser concentration, number average molecular weight, weight average molecular weight and polydispersity compared with un-aged samples were observed. The glass transition temperature measured using differential scanning calorimetery decreased by ~3°C. The decrease was attributed to the initial denitration reducing the energy of bond rotation and shortening the polymer chains, both factors reducing the energy required for movement. Modulus values determined from dynamic mechanical analysis temperature scanning experiments, did not detect significant variation between un-aged and aged samples. Though it was considered that variations would be likely if a more extensive ageing program was completed. In order to evaluate propellant behaviour at very high and low frequencies, time temperature superposition (TTS) and creep testing were carried out. The TTS technique superpositioned data well, allowing future investigation of high frequency propellant properties. Creep testing was considered to be an appropriate approach, though the equipment available was not optimised for such testing. This thesis is concerned with understanding how propellants are manufactured from nitrocellulose, nitroglycerine and other constituents. It is also about how the propellants decompose during long periods of time in storage, and how these changes can be measured using thermal and mechanical methods. It is about how the physical, chemical and thermal properties of the propellant composition change throughout the manufacture. This is relevant as it could be used to develop more efficient manufacturing processes, allow operators to adjust processes to tailor product properties or be used to re-design manufacturing to compensate for a different starting material. The thesis also considers how and why the properties of the product change over the course of years of storage. A specific focus on whether changes in mechanical and thermal properties occur, and if so how they can be detected.

Browsing by Author "Gill, Philip P."

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