Browsing by Author "Flood, Nathan"
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Item Open Access Low hazard small-scale synthesis and chemical analysis of high purity nitroglycerine (NG)(Royal Society of Chemistry, 2015-10-06) Contini, Alessandro E.; Flood, Nathan; McAteer, Daniel; Mai, Nathalie; Akhavan, JacquelineA previously reported two-phase (99.5% fuming nitric acid/dichloromethane) batch method to prepare high purity 1,2,3-propanetriyl trinitrate (nitroglycerine, NG) was evaluated, simplified and adapted specifically for low hazard small-scale synthesis. The purity of the product, as determined by NMR spectroscopy, HPLC and IR spectroscopic analysis was found to be greater than 99%. The quick synthetic method is highly recommended when small amounts of highly pure NG are required for analytical and related purposes in the absence of a microreactor.Item Open Access Resonant acoustic mixing of polymer bonded explosives(2021-01) Claydon, Andrew J.; Gill, Philip P.; Kister, Guillaume; Gaulter, Sally; Flood, NathanCurrent 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.Item Open Access Solubility and chemical interaction of nitrocellulose in plasticisers(Cranfield University, 2016-11-07 09:10) Flood, Nathan; Parker, MatthewTechnical paper presented at the 2016 Defence and Doctoral Symposium. Abstract: Nitrocellulose (NC) is commonly used as an energetic binder in explosive and propellant formulations. During the formulation and casting stages NC can be mixed with a variety of plasticisers with the aim of tuning the mechanical properties of the charge to suit the specified requirements. Historically there have been issues with the solubility of NC in various plasticisers which has created manufacturing problems leading to failures of missiles.The research presented from two programmes of work funded by the WSTC, Propellant Bonding and Nitrocellulose: Degrees of Freedom, has investigated how NC interacts with three plasticisers; Triacetin (TA), Diallyl Phthalate (DAP) and Nitroglycerine (NG). The solubility was investigated using time-lapse microscopy and the chemical interaction was investigated using Attenuated Total Reflectance Infrared Spectroscopy (ATR-FT-IR) and compared with the five modes describing the swelling and dissolution mechanisms of wood and cellulose fibres.The mechanisms observed for nitrocellulose follow the dissolution modes described for wood and cotton fibres. It was found that TA had the highest solubility with respect to NC whilst NG had the lowest; variation in the swelling and gelation of NC has been rationalised by the crystallinity within the sample. Changes in the cellulosic fibrillar substructure of NC due to nitration and processing results in changes in its crystallinity. This variation of crystallinity subsequently affects the chemical interactions of solvent and plasticiser molecules with NC and the bulk movement of these molecules through the material. ATR-FT-IR demonstrates the presence of constructive bonding interactions between NC and TA or DAP, which manifests as swelling and gelation at the bulk-level. NG exhibits no apparent molecular bonding by IR measurement, and sorption only into the NC fibre, without the extensive swelling and gelation observed in the other regimes.