FAIR-CT97-3784 Optimisation of the production chain for high performance "light natural sandwich materials" (LNS) as a basis for scaling-up

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Biocomposites/Boards : FAIR Area 1.2 - Green Chemicals and Polymers Chain : Fibre

	Contract No:	FAIR-CT97-3784
	Date Prepared:	August 2001
	Source:	Progress Report

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Progress Report Abstract

Objectives

The overall objective is to provide the basis for scaling up the production of high performance "light natural sandwich" (LNS) materials by further development of the whole chain from the primary production of the stem raw material to the technical processing of LNS. This will be done by:

• Use of pure plant-based core foam matrix and bonding adhesives in top layers.
• A comparison of stem quality characteristics for 'LNS suitability' using different crops: Arundo donax, bamboo, Miscanthus, rye and Triticale.
• Improvement of the stalk raw material by developing an optimised cultivation method with emphasis on Miscanthus.
• Production and testing of pilot products in co-operation with commercial partner

Activities

The light natural sandwich material is being developed with wood-based outer layers and a core of evenly orientated hollow plant stems embedded in a matrix of natural foam. These natural sandwich materials are very light and extremely rigid. The production of LNS comprises an environmentally friendly primary production, manufacture, processing and disposal. LNS can be used for a broad range of applications. The work programme comprises three packages:

• Primary production
• Manufacture of LNS
• Presentation and production of LNS to customer specification

Progress

Primary production: Field trials including perennial crops Arundo donax, bamboo and Miscanthus have been carried out at different European locations in Denmark, Germany, Portugal and Italy. Genotypes of rye, wheat and triticale have been collected under the criteria of stem height, stem erectness and lodging resistance from gene banks, universities and plant breeders and were sown at Giesen, Germany. Grain yield was not a selection criterion. These genotypes form the basis of a specific germplasm pool concerning stem quality. To improve stem quality experimental factors, as plant- or sowing density, seeding date, N- and Si-fertilisation were varied for annual crops and to a smaller extent for perennials. Plant establishment and growth performance were measured in terms of shoot height, stem diameter, lodging resistance and associated traits. The trials on cereals showed that especially registered cultivars fulfil the demands for LNS core production in terms of lodging resistance, whereas genotypes from gene-banks showed a relatively low lodging resistance. The influence of treatments (fertilisation, seeding density, seeding date) had only little influence on stem length and lodging resistance.

Manufacture of LNS: A number of test products of natural sandwich materials have already been produced and strength parameters, e.g. bending strength, bending module transverse compression, transverse tension, k-value have been tested for single stems or LNS specimen. The current production path for LNS can be described and summarised as follows:

• Arranging of stems into blocs.
• Embedding of the stems in a foam matrix.
• Sawing the blocs into slices.
• Gluing of the covering material.

Depending on the application of the sandwich, the core material can be made from stems from a number of different plant species with differences in stem characteristics markedly influencing the stability, flexibility and the weight of the final LNS product. Miscanthus and bamboo have, so far, given the best results concerning stem handling and the production of the core materials. Compared to the perennial crops the use of cereal stems is advantageous regarding the stem weight. LNS with core materials made from rye or triticale has a lower weight and shows still satisfactory strength characteristics for many industrial applications. The development of a plant based foam made from polyol showing good hardening properties would enable the currently used gelatin foam (hardening takes too long) to be replaced.

Presentation and production of LNS specimens:It is aimed to substitute sandwich materials made from plastics or light metals regarded as 'high-tech' products and used in vehicle construction and transport systems. Other applications are also considered. Many companies have already expressed their interest in using LNS. In economic terms, the introduction of LNS to the market stands a good chance. The production costs of LNS at a technical scale are estimated to be 175 - 350 Euro/M³, far below those for plywood (500 - 850 Euro/M³⁾ or sandwich materials based on plastics (beginning at 1500 Euro/M³). However, the production of LNS is still on a laboratory scale. Upscaling to commercial applications is still hampered by a wide variation in stem quality and the lack of a harvesting technology for miscanthus.

Activities

During the course of the project so far, the following results have been achieved:

Primary production:

• Establishments of field tests with perennial and annual crops on ecological different regions throughout Europe in Denmark, Germany, Portugal and Italy.
• Knowledge on cultivation methods to improve lodging resistance.
• Knowledge on environmental factors influencing stem stability.
• Collection of genotypes of rye, triticale and wheat under the aspects of stem height, stem erectness, stem diameter and lodging resistance.
• Collection and propagation of miscanthus including M giganteus and recently clones of M sacchariflorus to evaluate stem weight, stem diameter and leaf fall.
• Progress in the development of a miscanthus harvester.

Manufacture of LNS

• Further development of the production path. -
• Production of LNS specimen using stems from perennial and annual crops as core material.
• Development of the sawing technology for core materials.
• Development of the method of foam injection.
• Development of a foam based on natural polyurethanes forming the matrix for the LNS core.
• Testing the characteristics of different foam formulations

Future actions

The next steps have already been started and will be further developed after the project support ends. The basic problems of the production path for LNS can be solved. We believe that LNS, as a new environmentally friendly product will have chances on the market. Therefore, future actions will concentrate on bringing industrial partners together to start a project on demonstration scale and to search for funding as a last step before commercialisation. In such a project, each individual element of the production path has to be connected and integrated with the following one, in order to enable an automated manufacturing process to be designed for upscaling LNS material production.