Speaker
Description
Polyurethanes (PUs) are versatile materials applicable across many industries namely for their excellent resilience and applicability in different forms: flexible and rigid; monolith and foam. In space industry they are used for instance in spacecraft as coating and potting materials for protection of electronic compounds and further in launchers as rigid foams for thermal insulation of cryogenic tanks for liquid propellants.
Results of a screening study (1) are confirming a great potential to replace the conventional PUs in the selected space applications by the newly developed eco-friendly hybrid non-isocyanate polyurethane materials (HNIPUs). The HNIPU materials are formulated with the aim to minimize health and ecological issues related to the use of toxic isocyanates that are main chemical compounds in production of traditional PUs. Sustainability aspect is also achieved using renewable resources, such as vegetable oils and/or their derivatives.
Our recent research in the framework of this project confirmed possibility to prepare non-isocyanate conformal coating and potting systems with bio-sourced mass content exceeding 50 wt. % and content of non-isocyanate-based hydroxy urethane bonds mass per total bond mass up to 100 %. Processing, thermo-mechanical and electrical properties are adjustable to meet requirements for industrial applications.
The currently developed HNIPU foam has been compared to the reference PU system CRE210VS (provided by Latvian State Institute of Wood Chemistry) and displays ca. 3.5 times higher density (0.163 g/cm3), about 10 times higher compression strength at 10 % deformation (1.85 MPa @ 25 °C) and almost 2 times higher conductivity (0.042 W/m·K @20 °C). Enhanced mechanical properties and increased thermal conductivity are related to higher density of the developed foam.
Scale-up of the HNIPU foam production by industrial PU spraying equipment as the next step of the study is feasible by optimization of foaming parameters with the aim to reach requirements of industrial processing and finer, closed-cell structure.
The developed HNIPU is a good candidate for further development of non-isocyanate based conformal coatings, potting and thermo-insulation PU foam materials applicable in space industry.
(1) ESA Contract No. 4000119685/17/NL/KML: „Development of „Green“ Polyurethane Materials for Use in Spacecraft and Launcher Applications“.
