Project: Modification of natural fibers for improved fiber/polymer composites
In the last decade, the demand for strong light-weight products in automobiles, trains, suitcases, sporting goods, furniture, etc. has led to an increase in the application of composite materials. The market of glass fiber reinforced composites is by far the largest: 7.5 million tons (51 billion euro) in the year 2010 and growing annually by 4%. More recently, a small portion of the market (11%) has been taken over by composites reinforced with natural fibers like flax, hemp, jute and sisal._x000D__x000D_This replacement is driven by the 20% lower weight of natural fiber composites. Furthermore, the ecological footprint of these fibers is smaller than for glass fibers, due to the large amount of energy required to produce glass. A market penetration of 10% and thus a replacement of 0.75 million tons glass fiber composites by natural fiber composites is an important step in the realization of the bio-based economy and is accompanied by an energy saving of 9.4 million MWh/a, which is 10% of the electricity use of a medium European country like the Netherlands._x000D__x000D_Up to now however, despite the increasing demand for light-weight and sustainable products by both industry and consumers, the market acceptance of natural fiber composites has been slow. This is caused by their lower strength compared to glass fiber products. Natural fibers are hydrophilic (water-attracting) and therefore have no affinity for the hydrophobic (water-repelling) polymers in which they are embedded in a composite, and the strength of a composite material is determined by just that affinity._x000D__x000D_The aim of this project is to make natural fibers hydrophobic, thereby introducing an attraction between fiber and polymer, resulting in sufficiently strong end-products to allow replacement of glass fiber reinforced materials._x000D__x000D_In literature, several hydrophobic compounds are known that react with natural fibers. Examples are water-repellent and soil- repellent finishes for textiles, compounds to make silicon-coated glass and compounds to make semiconductor silicates water-repellent. However, no industrial applications exist up to now, because the choice of a solvent for this process is problematic:_x000D_1) Water and ethanol are not suitable because these inactivate the hydrophobic reactant molecules._x000D_2) Fossil-based organic solvents are flammable, explosive and generally toxic. They do not combine with the demand for sustainability._x000D__x000D_In this project, compressed (also called supercritical) carbon dioxide (scCO2) is used as a solvent for this process. ScCO2 is technically, environmentally and economically the best choice of solvent:_x000D_- CO2 is chemically inert and does not inactivate the reactant._x000D_- All CO2 is easily recycled and no solvent residue reCOs in the fibers._x000D_- Because of its low viscosity and high diffusivity, scCO2 enables fast mass transfer and thus entails short process times._x000D_- After depressurization, the fibers are obtained clean and dry, which makes the supercritical process the only impregnation that does not need a washing and drying step._x000D_- CO2 is non-toxic, non-flammable GRAS solvent._x000D_- The overall process cost is 20-40 % cheaper compared to conventional solvents._x000D__x000D_In this project the scCO2 is used to dissolve the reactant molecules and transport them to the fibers, where they chemically react, making the surface hydrophobic. To allow fast implementation, commercially available reactive hydrophobication agents are used. The R&D focuses on the impregnation/reaction process in supercritical CO2, on the composite material and on the end product._x000D__x000D_First, the best hydrophobication agent is identified by screening 5 compounds that are all hydrophobic, soluble in scCO2 and able to react with natural fibers. Then, optimum process conditions are determined. Composite material and end-products are manufactured and their quality and performance evaluated. Finally, the economic viability and the environmental aspects of the process and the product are determined._x000D__x000D_The project aims at the whole glass fiber composite market in the future, but on short term, it focuses on 4 end products, representing different market segments:_x000D_1) Ski's: high value, low volume._x000D_2) Automotive construction parts: medium value, high volume._x000D_3) Building facade panels: low value, high volume._x000D_3) Train construction parts: medium value, medium volume._x000D__x000D_All 4 products will be made to facilitate further market introduction of the new composite and the products._x000D__x000D_The consortium includes 4 parties:_x000D_- FeyeCon Carbon Dioxide Technologies (SME, Netherlands), global leader in the development of supercritical fluid technology_x000D_- NPSP Composieten B.V. (SME, Netherlands), a developer and supplier of composite materials containing natural fibers_x000D_- Bcomp Ltd. (SME, Switzerland), designing and marketing natural fiber composites with focus on sports and leisure applications_x000D_- Scott Sports S.A. (Large company, Switzerland) does not apply for subsidy, is involved as subcontractor and launching customer
| Acronym | IBC (Reference Number: 6961) |
| Duration | 01/03/2012 - 31/01/2015 |
| Project Topic | This project develops technology to produce sustainable composite materials. This is realized by making natural fibers hydrophobic in a solvent free process. Envisioned products are sports goods (ski's), automotive parts, building materials, etc. where glass fibers are replaced by natural fibers. |
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Project Results (after finalisation) |
Fiber matrix adhesion is usually not optimal for natural fiber composites. This property is very important if stresses occur in a laminate perpendicular to the fiber orientation. Besides, flax fibers tend to uptake humidity from the environment. The fibers swell/shrink during this process and the fibers can break out of the matrix. With fiber treatments the humidity uptake could possibly be minimized._x000D_The aim of this project is to make natural fibres hydrophobic, thereby introducing an attraction between fibre and polymer, and decrease of moisture absorption, resulting in sufficiently strong end-products to allow replacement of glass fibre reinforced materials. In the frame of the Eurostar project, natural fibres fabric has been treated using supercritical CO2 in order to confer theses new properties in an efficient and sustainable process. _x000D__x000D_Results were only slightly better compare to untreated fibres: no improvement of moisture absorption or mechanical performances was noticed even though high surface hydrophobicity was achieved. _x000D_Therefore, this technology with the current chemical treatment tested (10 in total with different process conditions) is not suitable at this stage to improve natural fibres performances in composites. _x000D_However, it is suitable to treat natural fabric when surface hydrophobicity and resistance to liquid water is required. This potential commercial application will be further studied. |
| Network | Eurostars |
| Call | Eurostars Cut-Off 7 |
Project partner
| Number | Name | Role | Country |
|---|---|---|---|
| 3 | BComp Ltd | Partner | Switzerland |
| 3 | FeyeCon Carbon Dioxide Technologies | Coordinator | Netherlands |
| 3 | NPSP Composieten B.V. | Observer | Netherlands |