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Biomass-based furan resins have more than 50 years of application history, especially in the foundry industry. Recently, TransFurans Chemicals developed user-friendly furan resin systems which and have application potential in a variety of composite areas. This article presents an overview of the development of new furan resins in composite applications.
(Published on January - February 2008 – JEC Magazine #38)
DR. IR. HANS E. HOYDONCKX, BUSINESS DEVELOPMENT MANAGER
DR. IR. WIM M. VAN RHIJN, GENERAL MANAGER TRANSFURANS CHEMICALS
Furan resins are thermoset condensation resins derived from renewable resources. Produced from pentose sugars, furfuryl alcohol or its prepolymers make up the raw materials of furan thermosets. Current advancements in formulation technology render these resins appropriate for composite production. Hot compression moulding is a proper technique to produce naturalfibre- reinforced composites (NFRC) from furan resins. These biobased NFRC are fit for the production of interior trim parts in automotive. For this application, a furan resin system was developed to be processed with short cycling times (
Furfural, the raw material for furfuryl alcohol, is produced from the hemicellulosic part of agricultural wastes. A controlled, hightemperature digestion of this pentose-based fraction yields furfural.
With biomass as the sole raw material, it is a renewable and CO2- neutral chemical (Figure 2). Technically, furfural can be produced from any raw material which contains pentose. On an industrial scale, the pentosan (hemi-cellulose) content, price, local availability and cost of collection, transportation, and handling of raw materials determine overall profitability. Corncobs and bagasse from sugar cane are the major industrial feedstocks for furfural production.
Novel biomass-based furan resins
TFC recently developed a new range of resins based on prepolymers of furfuryl alcohol. BioRezTM and FuroliteTM are two novel resin systems which are suitable in a wide range of formulations as the matrix for binding fibreglass, rockwool and carbon fibre, as well as natural fibres such as wood, flax, sisal and jute.
BioRezTM natural-fibre-reinforced composites
Natural-fibre-reinforced composites are established products in today’s automotive industry. All major OEM’s have now models with interior or even exterior trim parts made from flax, hemp, sisal or wood fibres formed with a thermoset or thermoplastic resin system. Current thermoset resin systems feature epoxy, polyurethane, acrylic and phenolic binders, which are all derived from fossil resources. With the introduction of BioRezTM, a renewable thermoset binder is now available for NFRC. Prepolymers of furfuryl alcohol are the base material of BioRezTM resins (Figure 3).
These resins contain no organic solvents or free furfuryl alcohol and can be formulated with different viscosities and curing characteristics. BioRezTM Automotive is a specially designed sprayable resin for the production of natural-fibre-reinforced composites by hot compression moulding. It is a onecomponent system which is cured at elevated temperatures (>150°C) to yield a crosslinked polymer. The resin is sprayed on natural fibre felts. Impregnated felts are placed in a hot compression mould (Figure 4).
With a press temperature of 190°C, panels can be produced with cycling times below 50 seconds. The typical requirements of interior trim parts can be fulfilled by adjusting the fibre type, specific weight of the natural fibre mat, and amount of resin used as matrix.
Prototype production and testing was performed in cooperation with Polytec Automotive GmbH & Co. The model product for this material was a BMW door panel (Figure 5).
The production of BioRezTM Automotive NFRC can be carried out on standard installations for impregnation and hot compression moulding. Short cycling times allow production of large quantities. BioRezTM NFRC have mechanical properties comparable to epoxy/PU NFRC and show low VOC and FOG emission values.
FuroliteTM resin for resistant materials
FuroliteTM resins are formulated for applications where stability under heat, fire or corrosive environments is needed (Figure 6).
To fulfil these requirements, the resins are mostly reinforced with glass fibres, carbon fibres or mineral fillers. They can be used to make components highly resistant to fire with a very low smoke toxicity. These resins are based on purified furfuryl alcohol polymers. They are generally formulated as two-component resins where the hardener is mixed with the liquid resin prior to application. FuroliteTM components can be made by a range of traditional composite manufacturing techniques like vacuum infusion, hand lay-up, spray-up, filament winding and pultrusion when reinforced with fibres. With a mineral or graphite filler, the formulations are applicable as a cementing binder for chemicalresistant polymer concrete. The resin is mostly applied as a twocomponent system that features low-temperature curing. Resin and catalyst are mixed prior to application. Curing temperatures are generally below 100°C.
With BioRezTM and FuroliteTM, a new generation of furan resins is presented to the industry. These resins can find versatile applications such as matrix composite manufacturing.