Novel Polyurethanes Based on Recycled Polyethylene Terephthalate: Synthesis, Characterization, and Formulation of Binders for Environmentally Responsible Rocket Propellants.

Florin Marian Dîrloman,Florentina Alexe,Robert Țincu,Gabriela Toader,Răzvan Petre,Raluca Elena Ginghină,Traian Rotariu,Tudor Viorel Țigănescu,Alina Elena Coman,Monica Duldner,Edina Rusen,Aurel Diacon,Adi Ghebaur,Mihai Ionuț Ungureanu

doi:10.3390/polym13213828

Abstract

Novel polyurethane-based binders, specifically designed for environmentally responsible rocket propellant composites, were obtained by employing the polyester-polyols that resulted from the degradation of polyethylene terephthalate waste. A new class of “greener” rocket propellants, comprising polyurethanes (based on recycled PET) as the binder, phase stabilized ammonium nitrate (PSAN) as the eco-friendly oxidizer, and triethylene glycol dinitrate (TEGDN) as the energetic plasticizer, together with aluminum as fuel and Fe2O3 as the catalyst, is herein reported. The components of the energetic mixtures were investigated (individually and as composite materials) through specific analytical tools: 1H-NMR, FT-IR, SEM-EDX, DTA and TGA, tensile and compression tests, DMA, and micro-CT. Moreover, the feasibility of this innovative solution is sustained by the ballistic performances exhibited by these composite materials in a subscale rocket motor, proving that these new formulations are suitable for rocket propellant applications.

Highlights

Solid rocket propellants are a particular class of energetic materials that are developed to ensure the propulsion of spacecrafts, missiles, and rockets toward a target
To demonstrate that the polyurethanes are suitable for this type of a4p.pCliocantcilouns,itohnesy were subjected to structural and rheological characterization (1H-NMR, FT-IR, and viscosity analysis), while the new composite propellants were subjected to mor
To highlight the advantages brought by this new “green” approach, in comparison with state-of-the-art hydroxylterminated polybutadiene (HTPB) binders, we further summarized the most important achievements of this study

Summary

Introduction

Solid rocket propellants are a particular class of energetic materials that are developed to ensure the propulsion of spacecrafts, missiles, and rockets toward a target. Solid rocket composite propellants are typically based on a heterogeneous combination of distinct compounds that serve as fuel, oxidizer, burn-rate modifiers, and binder [1,2]. In the case of energetic materials, they have a dual purpose, as a binding agent and as an organic fuel [1,2]. These polymeric matrices are used for binding other solid components of the rocket propellants, to protect them against environmental agents and to confer a certain geometry and mechanical strength. Together with the oxidizers and additives, the solid fuel is introduced in the polymeric matrix to ensure homogeneity, protection, and proper mechanical characteristics of the energetic mixture [2,8,12–16]

Methods

Results

Conclusion