Browsing by Author "Wilkinson, Peter J."

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    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.
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    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.