SURPASS will develop SSRbD alternatives with no potentially hazardous additives through industrially relevant case-studies, targeting the three sectors representing 70% of the European plastic demand
Case Study #1 - Building Sector
New bio-sourced polyurethane (PU) to replace PVC for windows frame.
PVC is one of the main polymers used in buildings for its outstanding mechanical and durability properties. However, its production (needing large amount of chlorine, and forming highly hazardous organochlorinated compounds) and degradation along its lifecycle pose environmental issues that led to global initiatives to reduce PVC consumption.
PU foams are the best isolation material affordable on the present market. It has the potential to replace PVC in some building applications, for example insulation of window frames, for which IND developed a finished product ready for market. This product is as solid as wooden profiles, so it does not need metal reinforcement as used with PVC (prevent from binding – but responsible for additional C-footprint). It has proven an extremely high insulating degree, with a Heat Transmittance more than 2 times lower than that of PVC (CE marking tests results).
This product is partially bio-based (targets 50-75% overall content of bio-based and renewable materials on a weight basis) using natural oils, lignin and sugars – not competing with ‘higher’ uses according to the biomass value pyramid. In case of natural oils, those produced for biodiesel industry do not compete with food industry. Lignin is not indeed competing, and sugars are in decline use in the food industry (sugar industry is looking for new applications out of food sector). It results in a highly reduced C-footprint of the first life cycle - unlike PVC from fossil sources.
Its inherent properties allow some hazardous additives to be removed, for example organo-halogen fire-retardant additives (as used in PVC) that can be efficiently replaced by innocuous mineral nitro-phosphate salts. However, the chemistry of PU (highly crosslinked material) makes it difficult to recycle - it cannot be melt-reprocessed like a thermoplastic. The current solution consists in micronizing old PU/ production waste and
using it as a filler in new formulations. This process allows recycling percentages of no more than 50% - and still less than 30% of thermoset PU is effectively recycled (remaining is landfilled, incinerated). SURPASS proposes to investigate further the use of vitrimer chemistry to increase recyclability of the PU and enable up-cycling. Vitrimer chemistry lies on the creation of Dynamic Covalent Networks (DCN), which under controlled conditions can tie and untie polymers chains, resulting in a final product with similar properties than the initial one. Vitrimers have been conceptualized based on different chemistries, thus several choices for further developments. Approaches described in the literature design a vitrimer PU that allows reprocessability while keeping PU-like properties (i.e. combined advantages of thermoplastics and thermosets), at a proof-of-concept stage. The project aims to modify the IND bio-based PU structure through introduction of dynamic chemistry (oxime-carbamate) directly in the PU backbone, thus converting it in a vitrimer, reprocessable through compression molding at low temperature.
Case Study #2 - Transport Sector
Fire resistant epoxy-vitrimer materials for sustainable composites for the railway sector
Fire resistant epoxy-vitrimer materials for sustainable composites for the railway sector
The interest in using composite materials for structural applications in many different industries has increased significantly in the past decades. Currently, in the railway sector, composites are mainly and extensively used for several interior applications and in secondary structure applications. They would yet have a huge interest as lighter alternatives to metals – enabling less energy consumption.
However, the application of composite materials in rolling stocks (primary structures) is ruled by Fire, Smoke and Toxicity (FST) requirements according EN45545. As glass- or carbon-based fiber reinforcements have good fire properties, it is mainly the resin that has to be improved regarding fire resistance.
Recently, some composites have been developed that meet these regulations (e.g. Results from Mat4Rail project) but they are not sustainable at end-of-life since they are not intrinsically recyclable. Being thermoset (once cured it cannot be reshuffled), their end-of-life options are very limited, and they normally end up in landfill or incinerated.
SURPASS project targets the development of epoxy vitrimers that fulfil all railway FST requirements, while meeting the required mechanical performance and being intrinsically recyclable at end-of-life – thus preventing the market from being overflown with emerging non-recyclable composites made up with epoxy-based thermosets.
To overcome this handicap, dynamic covalent chemistries have been applied at research level during the last decade on thermoset polymers, resulting in innovative unconventional thermoset polymer networks. It is worth noticing that most of the state-of-the-art examples of dynamic thermosets are based on soft, non-structural materials, with a few exceptions: they are not suitable candidates for the railway industry.
CID has thus developed a unique new epoxy vitrimer system that is (i) easy to synthesize from readily available starting materials in a scalable manner, (ii) have fast stress relaxation at high temperature (vitrimer behavior) without the need for a catalyst, and (iii) easily applicable for the manufacture of
(re)processable, repairable and recyclable (3R) Fibre Reinforced Plastic Composites (FRPC). This dynamic epoxy system is based on the reversible exchange of aromatic disulfides.
Regarding the improvement of the fire resistance, the trend is to replace halogen-based, especially bromine-based, Fire Retardants (FRs) by halogen-free, less toxic and ecologically friendly alternatives. The most common strategies to obtain flame retardant properties in halogen-free epoxy resin formulations are, among others to use inorganic flame retardants like aluminium hydroxide (ATH), modified inorganic additives like ammonium polyphosphate (APP), several different organophosphorous compounds, etc.
Novel flame retardant strategies will be introduced in the epoxy vitrimer matrix by a) increasing the flame
retardancy of the polymer backbone by using monomers with low flammability and b) the incorporation of novel dynamic flame retardants which are linked to the epoxy vitrimer by dynamic covalent bonds.
During the product lifetime, the dynamic FR is covalently bonded to the polymer making the product safe in terms of environmental toxicity and fire protection. In the product’s end-of-life phase, the dynamic FR is debonded during recycling. This allows to adjust the FR amount as well as completely remove it from the intrinsically recyclable epoxy vitrimers, making the FR and also the epoxy vitrimer much more sustainable than current polymers using a reactive FR. The material properties can thus be adapted to the needs of the next epoxy vitrimer life cycle.
Case Study # 3 - Packaging Sector
MultiNanoLayered (MNL) films to replace multi-layer films for food packaging
Multilayer plastic films are currently used as packaging for the protection of food – because of their unique barrier properties enabling significant extension of food preservation. They are traditionally composed of multiple highperformance layers (e.g. polyolefins (PE (polyethylene) and PP (polypropylene) - 55% of multilayers streams), PA (polyamide), EVOH (Ethylene and Vinyl Alcohol copolymer), etc. but also aluminum or cardboard). Most current designs and the widespread absence of sorting and recycling technologies for such multilayers make them unsuitable for recycling in an economically and environmentally sustainable way.
In addition, chemical compatibility being a key criterion in obtaining quality multilayer films, it is often necessary to use compatibilizer to promote bonds at the interface between the various layers24 that can potentially migrate – severe issue in food packaging application – and become contaminants for potential reprocessing. SURPASS proposes to evaluate feasibility to develop MNL produced polymeric systems. In the MNL process, the combination of polymers at the interfaces is forced by the flows instead of governed by chemical interactions between components (Van der Waals interactions). This effect of nano-structuring allows the realization of multinanocomponent films with good barrier, mechanical and optical properties, theoretically without compatibilizing agents, in order to reduce material costs and improve the recyclability of the final product.
MNL is a continuous process which allows in a single step to combine one or several materials in a film composed of up to several thousands of alternating layers in the nanometric range. The tortuosity it creates ensure a high gas barrier performance.
Films produced by MNL can theoretically be indefinitely recycled through extensional compounding and a reprocessing into a new MNL film. Extensional compounding might however be responsible for degradation of products
(because of shear stress, temperature) and release of potentially harmful substances, in particular in view of up-cycling in the food packaging value chain. It is foreseen during SURPASS project to develop the necessary decontamination process to enable such up-cycling. Current state-of-the-art MNL films still contains up to 15% compatibilizers that could hinder recycling process and also migrate to food when used in food packaging. It is an objective of the SURPASS project to develop MNL films containing 0% of compatibilizers. Furthermore, MNL films have been brought to TRL5 only for PE/EVOH compounds. It is intended to the project to extend knowledge and know-how related to PA/PE blends.
SURPASS will study synergies between MNL and bi-axial stretching to reduces the film thickness to a suitable level for various applications such as packaging film and provides significant enhancement of the film properties, including enhanced barrier properties