New green polymer composites processed by Additive Manufacturing for “clean space” applications
Additive Layer Manufacturing (ALM) is an intrinsically green technology as it allows using less material than when using conventional manufacturing techniques. In terms of carbon footprint reduction, it is suggested that there are five primary environmental and sustainability benefits to the adoption of additive manufacturing , i.e. containment of the required raw materials amounts, reduction of the need for energy intensive and wasteful manufacturing processes, design of more efficient products with better operational performance, reduction of the final product weight and possibility to manufacture the parts closer to the consumption point . A major contribution to satellite demissability could be achieved by merging the ALM contribution to the use of polymers. Indeed, these materials have far lower melting temperature than metals and would likely burn during atmospheric re-entry. In fact one of the space debris mitigation requirements is the removal of space systems that interfere with the LEO region, not later than 25 years after the end of the mission . At present, the choice of ALM processable polymers is relatively limited, particularly in the case of fused deposition modelling (FDM) technology. Therefore together with the development of ALM technologies, the range of materials available for such process needs to be increased . In this framework, the aim of this work, following a bottom-up methodology, is to produce new green polymeric and composite materials by ALM processes, starting from the modification of the raw material composition, to improve the component final performance in non structural space applications. Polyetherimmide (PEI) was chosen as polymeric matrix due to its elevated mechanical properties and processability, thermal resistance, high strength and stiffness and broad chemical resistance, unlike most other amorphous thermoplastics . Biosilica (derived from the skeletons of diatoms, a class of algae) and/or nanoclays (e.g. montmorillonite, bentonite, cloisite and halloysite) were chosen as green reinforcing fillers . Different amounts of fillers were tested to identify optimal composition. Samples were prepared by means of solvent casting and melt mixing processing, and their Morphology (scanning electron microscope, FEG-SEM), thermal (differential scanning calorimetry DSC), and thermo-mechanical properties (dynamic mechanical thermal analysis DMTA) as well as mechanical performance ( tensile tests) of produced materials were analysed and assessed.