Browsing by Author "Gaulter, Sally E."

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    Cross-linking of hydroxyl-terminated polyols with triethyleneglycol diglycidyl ether: an alternative to toxic isocyanates
    (Wiley, 2018-01-16) Dossi, Eleftheria; Akhavan, Jacqueline; Gaulter, Sally E.; Williams, Richard G.; Doe, William J.
    Isocyanates are highly reactive and toxic substances with severe health effects. Certain diisocyanates are restricted under REACH – The European Regulation on Registration, Evaluation, Authorisation and Restriction of Chemicals. Triethyleneglycol diglycidyl ether (TEGDGE) was used as an alternative to toxic isocyanates for the cross-linking of hydroxyl-terminated pre-polymers at 70oC. The effect of three curing accelerators was determined while following the reaction kinetics by 1H-NMR spectroscopy and differential scanning calorimetry (DSC). Polybutadiene (Poly BD R45HT-LO) and acrylic ester (HyTemp 4454) successfully cross-linked in 7–10 days to produce thermally stable networks with low glass transition temperatures, as observed by DSC. Pre-aging the polybutadiene resin promoted cross-linking with TEGDGE. Four energetic compositions were then prepared using cyclotrimethylenetrinitramine (RDX) and pentaerythritoltetranitrate (PETN) as fillers, and polybutadiene (Poly BD R45HT-LO) and acrylic ester (HyTemp 4454) as binders. Both binders successfully cross-linked with TEGDGE in the presence of RDX and PETN, but only PETN was found to be chemically compatible with the cross-linked polymers. These results show that TEGDGE is suitable as a replacement for toxic isocyanates for the cross-linking of hydroxyl-terminated polyols.
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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.