The concept of the project lied in the full recovery of glass-fiber aircraft insulation materials and in the recycling of their constituents into new, competitive materials for building applications. In this context, the project envisaged recovery of the glass fibres, the polymeric bags and the thermosetting resin used as binder and aimed to develop and apply alternative routes for their recycling, including closed and open-loop systems, as well as primary and secondary recycling processes.
The final products of the project included:
- New insulation materials;
- A series of concrete samples incorporating alternative recycled materials (i.e. glass fibres, glass microparticles and polymeric microparticles);
- Glass fibre-reinforced polymer composites.
More specifically, following the acquisition and characterization of the end-of-life a/c insulation materials, their individual constituents were recovered and characterised to assess their processability. The proposed recycling routes for each constituents were summarised as follows:
1) Glass fibres:
- Closed loop recycling into new insulation materials;
- Use as reinforcement in polymer-matrix and concrete composites;
- Preparation and treatment of glass microparticles and their application in concrete.
2) Polymer bag materials:
- Utilization of polymeric microparticles as concrete filler;
- Polymer recycling into composite materials.
3) Thermoset resin:
- Utilization as sand substitute in concrete.
All products were characterised and optimised in terms of performance and cost to ensure their acceptance in the market, which is a prerequisite for the economic viability of the recycling processes developed. Overall, environmental, economic and technological benefits were expected from the establishment of the proposed recycling routes.
The concept of the IMAGINE project lied in the full recovery of glass-fibre aircraft (a/c) insulation materials and the recycling of their constituents, which were: a) glass wool fibres and b) polymeric bags, into new products for the construction sector. This objective was of high importance as today there are only limited recycling options for such insulation materials and environmental, economic and technological benefits are expected from the establishment of the proposed recycling routes.
In IMAGINE project the work is organized in three technical work packages.
Within the project, deliveries of two batches of end-of life aircraft insulation materials were realised after the dismantling of two aircrafts. As their production date was before 1995 and such materials are possibly carcinogenic, full characterisation carried out. The characterisation results showed that they could be potentially hazardous for health and the consortium decided to continue the experimentations with commercial insulation materials exhibiting similar characteristics to the insulation material currently used in aircrafts, while from the old insulation material it was decided the consortium was to use only the polymeric bags for recycling.
The polymeric bags were separated from the insulation material and further processed by shredding and densification in order to produce polymeric pellets ready to be used for the production of various new products. Furthermore, within WP2, two commercial insulation materials with recent production date, where purchased and after their characterizations, they were shredded and used for the production of the various new products in the next WPs.
In WP3 which addresses primary recycling of materials, the recovered glass fibres (GF) and the polymeric bags were utilised for the development of cement/concrete and polymeric composites.
Various formulations of concrete samples incorporating different ratios of GF, as an aggregate partial replacement, were developed and specimens of lightweight concrete, cladding panels and paving blocks were produced.
As alkali-silica Reactivity between glass and the alkaline environment of the concrete mixtures is an undesirable phenomenon, a study carried out showed that GF in the percentages used for the produced cementitious products can be considered innocuous. Moreover, for promoting pozzolanic reactivity, a local natural super pozzolan was used at appropriate proportions in the cementitious mixtures.
The lightweight concrete samples produced with incorporation of chopped GF, as replacement of sand, exhibit very good mechanical properties while Paving blocks with satisfactory characteristics can also be produced, in case a special pressing machine that incorporates vibration and compaction is available.
The cladding panels produced with incorporation of chopped GF as replacement of sand exhibit similar mechanical and physical properties compared to the blank ones, while the ones produced with incorporation of pellets from recycled polymeric bags, exhibit improved mechanical properties.
Therefore, the recycled polymeric bags and the glass fibres can effectively be used up to a certain percentage for the production of various cementitious products like cladding panels, paving blocks and lightweight concrete with good mechanical and physical properties implying that such products can easily reach a competitive market.
The recycled polymeric bags and the shredded GF were also used for the development of polymeric matrix composites by the injection moulding process. It was proved that the new developed products provide an environmentally friendly profile in combination with adequate properties.
In WP4, addressing secondary recycling routes, the shredded GF were incorporated in a clay matrix and small clay bricks were produced, exhibiting similar properties with the reference samples in terms of mechanical properties and porosity but using a lower sintering temperature.
Besides, the GF were also used with recycled polyester fibres and bio-component fibres for the production of new insulation glass wool material. The new developed products exhibit satisfactory properties compared to existing commercial ones and have an enhanced environmental profile, which also implies that they can easily reach a competitive market.