SaferWorldbyDesign: Lignin-based Materials Development and Manufacturing according to SSbD principles

This presentation is based on ongoing research that is being undertaken under the remit of the project entitled “Multifunctional biophenols for safe and recyclable materials” (BioPhenom). The project is funded by the European Commission (Grant Agreement No: 101135107), Innovate UK (Grant Agreement No: 1005409) and Swiss State Secretariat for Education, Research and Innovation (Grant Agreement No: 24.00212). The overall aims of the BioPhenom project are: (i) to replace substances of very high concern with bio-based alternatives; and (ii) the development of safe, sustainable and recyclable materials and manufacturing processes.

This presentation consists of two inter-related themes. The first part of the talk will focus on the development and on-site demonstration of an environmentally friendly filament winding (EFFW) technique for the production of fibre reinforced pipes and pressure vessels. The second part will address the production of carbonised nano-fibres using two classes of naturally occurring biopolymers, namely, lignin and tannin.

Conventional filament winding  is an established manufacturing technique for the production fibre reinforced composite pipes and pressure vessels. In this manufacturing process, the reinforcing fibres are impregnate using a resin bath and the impregnated fibres are wound onto a rotating mandrel, and subsequently, the resin system is cross-linked.  This manufacturing has a number of issues that need to be addressed.  Firstly, the components of the resin system (for example, an epoxy resin and a cross-linking agent that is referred to colloquially as the hardener) have to be weighed out manually to the required stoichiometric ratio and mixed thoroughly until a visually assessed homogeneous colour is determined. The resin bath has to be topped up manually as the liquid level drops as a function of the processing time. Due to the nature of the manufacturing process, the impregnated fibre have to be traversed back and forth across the rotating mandrel; this results in the impregnated fibres to rub against the guide pins leading to drips. In order to alleviate these issues, in the EFFW process, the fibres are spread to reduce their thickness (to accelerate the impregnation rate). Instead of using a resin bath, the resin and hardener are stored separately and are pumped via precision gear pumps to a static mixer; this negates the need for manual weighing and mixing and the desired stoichiometry is delivered. A custom-designed impregnation device is used to deliver the required quantity of the mixed resin system to the spread fibre bundles. The design of the impregnation unit is such that its volume is significantly smaller that a conventional 5 litre resin bath. The primary advantages of the EFFW manufacturing process when compared to the conventional method are: (i) it requires a fraction of the volume of solvent that is required to clean the equipment at the end of production; (ii) the volume of residual resin retained in the impregnation unit is reduced significantly; and (iii) the time required to clean the equipment for the EFFW methods is reduced significantly.

Carbonised fibres from lignin and tannin: The primary precursor that is used for the production of reinforcing carbon fibre is acrylonitrile. This precursor is derived from petroleum and it is associated with a number of hazard numbers/statements: H225 - Highly flammable liquid and vapor. H301 + H311 + H331 -Toxic if swallowed, in contact with skin or if inhaled. H315 - Causes skin irritation. H317 - May cause an allergic skin reaction. H318 Causes serious eye damage. H335 May cause respiratory irritation. H350 - May cause cancer. H411 - Toxic to aquatic life with long lasting effects. Therefore, it was considered as an idea candidate for a BioPhenom case study to consider options to replace it with relatively inert precursors that are derived from biomass. The candidate materials selected were lignin and tannin. 

The micrographs below demonstrate that lignin and tannin fibre can be produced by electro-spinning and that they can be carbonised. The next task is to enhance the mechanical properties of these fibres.  Follow-on research will be reported at a later date where bio-based and recyclable filament wound tubes will be demonstrated.

Speaker: Gerard Fernando (University of Birmingham)