1. Introduction
Composite propellants used in solid-fuel rockets commonly consists of an oxidizer, the most used being ammonium perchlorate, fuels such as powdered aluminum, compounds that control the burn rate (catalysts or inhibitors), and various other additives. All these powdery materials are held as a one solid piece by a polymeric binder that also serves as fuel [1]. The heavily used binder in this regard is the elastomeric polyurethane based on hydroxyl-terminated polybutadiene (HTPB), crosslinked with aromatic or aliphatic diisocyanates. The vast majority of polyols used in polyurethane production, HTPB included, are obtained indirectly from fossil fuels such as crude oil or natural gas. The need to limit the use of petroleum has led to the research and development of polyols made from plant-derived renewable sources, such as vegetable oils [2], starch, proteins, lignocellulosic mass [3], etc., but also by chemical recycling of polymers at the end of their life, namely polyurethanes, polyesters or polyamides. Poly(ethylene terephthalate)-PET, being one of the widely used polymers [4] and also being susceptible to depolymerization via glycolysis to produce polyols [5], is intensively studied in this regard. In the current study, we aimed to show the advantage of novel polyurethanes based on polyols made from plant-derived renewable sources or recycled PET that represent an environmentally friendly system as new binder alternatives for composite propellant rockets. The current study, aims to highlight the advantages of using novel polyurethanes, based on polyols made from plant-derived renewable sources or recycled PET, as new binder alternatives for composite propellant rockets.
2. Materials and Methods
Polyurethanes have been synthesized at varying NCO:OH ratios, using isophorone diisocyanate(IPDI) and three types of polyols: commercial polyether polyols, a polyol synthesized by the glycolysis of PET, and the commonly used HTPB polyol.
3. Results
Elastomeric polyurethanes based on IPDI and commercial polyether polyols, the polyol synthesized from recycled PET, and HTPB were synthesized and their chemical, physical, and mechanical properties were assessed using modern characterization techniques and then comparatively studied. It was shown that the polyurethanes based on commercial polyols and the polyol made from PET possessed mechanical properties comparable to those of the widely-used HTPB elastomer.
4. Conclusions
The study revealed that “green” polyols can be promising candidates for the replacement of petroleum-derived HTPB, with the potential use in composite propellant formulations for rockets used in civilian and military applications.
Author Contributions
Conceptualization, T.-V.I.; methodology, T.-V.I., A.F. and A.Z.; validation, T.-V.I., A.S. and A.F.; formal analysis, S.-V.D. and C.-M.D.; investigation, T.-V.I., A.-L.C. and A.-M.G.; resources, T.R.; writing—original draft preparation, S.-V.D. and A.Z.; writing—review and editing, T.-V.I.; visualization, C.-M.D.; supervision, A.-L.C. and A.-M.G.; project administration, A.Z. and T.R.; funding acquisition, T.-V.I. and A.Z. All authors have read and agreed to the published version of the manuscript.
Funding
This research was funded by Executive Unit for Financing Higher Education, Research, Development and Innovation (UEFISCDI), grant. No. 75PTE/2022 E-CORA and Program 1—Development of the national research and development system, Subprogram 1.2-Institutional performance-Projects to finance excellence in RDI, Contract no. 15PFE / 2021.
Institutional Review Board Statement
Not applicable.
Informed Consent Statement
Not applicable.
Data Availability Statement
The supporting data are available from the corresponding author.
Conflicts of Interest
The authors declare no conflict of interest.
References
- Chaturvedi, S.; Dave, P.N. Solid Propellants: AP/HTPB Composite Propellants. Arab. J. Chem. 2019, 12, 2061–2068. [Google Scholar] [CrossRef] [Scilit]
- Petrović, Z.S. Polyurethanes from Vegetable Oils. Polym. Rev. 2008, 48, 109–155. [Google Scholar] [CrossRef] [Scilit]
- Malani, R.S.; Malshe, V.C.; Thorat, B.N. Polyols and Polyurethanes from Renewable Sources: Past, Present and Future—Part 1: Vegetable Oils and Lignocellulosic Biomass. J. Coat. Technol. Res. 2022, 19, 201–222. [Google Scholar] [CrossRef] [Scilit]
- Plastics—The Facts 2022. Available online: https://plasticseurope.org/knowledge-hub/plastics-the-facts-2022/ (accessed on 11 September 2023).
- Vaidya, U.R.; Nadkarni, V.M. Polyester Polyols for Polyurethanes from Pet Waste: Kinetics of Polycondensation. J. Appl. Polym. Sci. 1988, 35, 775–785. [Google Scholar] [CrossRef] [Scilit]
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content. |
© 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).