AGRE-0050 Fibre and Pulp Production from Unconventional Biomass Fibreplastic Blending Trials and Applications

Contacts
Summary Information



To find similar Items, click on a keyword below:
Biocomposites/Boards : Drying/Pretreatment : ECLAIR Cluster II - Lignocellulose : Fibre : Process Engineering : Pulping

SUMMARY

A number of techniques are used to produce reinforced plastic forms for use as parts of vehicles, containers, furniture, etc. Conventional products are composed of a plastic matrix into which is embedded glass fibre to provide strength, together with an inert filler such as calcium carbonate and various additives which increase cohesion of the final matrix. The purpose of this project was to see if natural plant fibres could be used as substitutes for glass fibre in a specific use - the manufacture of car body parts. The underlying reasons for doing this related both to creating opportunities for farmers to produce non-food crops and to the possibility of making components which are biodegradable when disposed of. The choice of fast growing, nitrogen fixing (leguminous), species (including broom) which grow as weeds throughout the EU enabled low cost production based on short rotation cycles of about three years. Methods were developed for the complete production scheme, from harvesting through decortication, defibrating, web-forming and moulding - followed by product evaluation. Problems were not found in applying these techniques, but more work is required in formulation of the mix to enhance binding between fibres and the matrix.

INTRODUCTION

Many articles and types of cladding used in building are based on fibres or particles embedded in a resin or held together with some form of binding matrix. Such composite materials include, for instance, glass fibre reinforced objects such as car body parts. The objective of this project was to investigate the feasibility of producing a new composite plastic material using agricultural raw materials which can be cultivated in marginal or set-aside land. The use of biodegradable pulp and natural fibre as filler or reinforcement in plastic composites instead of glass fibre and calcium carbonate is of interest in reducing the environmental problems of eventual disposal.

OBJECTIVES

The purpose of this project was to develop a new composite plastic material using agricultural raw materials. This included the following aspects:

1. production of biomass for experiments as well as investigating the feasibility of producing 15000-20000 tons of biomass per year;
2. development of procedures and machines to pretreat the raw biomass (harvester and chipper);
3. defibration of the biomass and refining of the fibres to make them suitable for further processing;
4. definition of the most suitable process for web formation, using different binders, calendering and embossing in a way which provides the mechanical properties required by various types of components;
5. the treatment of the fibre with additives to obtain a good linkage between them and the plastic matrix;
6. investigate the fibres from broom (Genesta).

ACTIVITIES

This project focused on the optimisation of cultivation and processing of shrub wood trees on marginal lands for fibre production for industrial purposes. The leguminous plants Robinia and broom (Genesta) were the most attractive in terms of yield and environmental impact. To improve the economics of fibre production from broom, new cultivation methods based on SRIC (Short Rotation Intensive Culture) were developed. Since broom is a leguminous plant it does not require nitrogen fertiliser, fixing nitrogen from the air through the Rhizobium symbiosis. No weed control is required due to their dense growth habit and high growth rate. Hence, no agricultural activity is required after planting. The crop may then be harvested every few years. It was found necessary to work with a very high plant density (from 10,000 to 20,000 plants per ha). The small diameter of the trunks of young plants facilitates machine harvesting. Once the plant had been harvested, methods were developed to defibrate the material in suspension with solutions of additives. This was achieved using a refiner consisting of a conical rotor and a stator, each provided with blades. With this it was possible to obtain a fibrous suspension, where fibre bundles are open, while woody pieces are broken - the two forming a heterogeneous suspension. This suspension was then thickened, pressed and dried. The fibres obtained had physical and chemical properties suitable for the following applications: The first method investigated was web production with a dry forming technology. In order to improve the quality of the final webs a defibrator was designed to break the material into single fibres while maintaining fibre length in a system which had both a reasonable throughput and an acceptable defibration capacity. The best system was an all-steel hammermill designed for producing fibre fluff out of treated or untreated pulp. Web formation was achieved using a fibre deposition system developed by Dan Web, which uses air rather than water. Several types of webs of different composition were obtained, based on either broom/Robinia fibres plus polyethylene or polyester fibres or on broom fibres plus polypropylene fibres. The first compound application used vegetal fibres in polyester resin for Resin Transfer Molding in which the process is initiated by pre-forming the reinforcement made from one or more layers (webs). The moulded parts have about 30% of reinforcement by weight. The alternative investigated was Bulk Molding, an injection technique that is used with a filler and a matrix (polyester resin, thermoplastic additive).

Conventional reinforcements are glass fibres and calcium carbonate. In this work, moulded parts of traditional composition were compared with parts made with vegetal fibres instead of glass fibres. Another possibility investigated was the use of vegetable fibres in a polypropylene matrix. This included injection molding of pellets made of 30-50% of broom fibres, 70-50% of polypropylene and about 1% of different additives as binder as well as compression molding of webs made of polypropylene plus vegetal fibres. The webs had about 50% of broom fibres. Very good results were achieved with both thermosetting and thermoplastic molding. The mechanical properties are high compared to those of glass reinforced composites. Following laboratory trials, Fiat Research Centre used the materials on industrial moulds to produce various car components. These included part of an inner door panel made by compression molding from a thermoforming mat made of polypropylene and broom fibres plus a small amount of binding. There were no problems in filling the mould cavity. Another part made was the lid of the dashboard glovebox. This used thermoplastic pellets moulded by injection. The pellets were made of 50% of polypropylene and 50% of broom fibres plus a little amount of binder. No problems occurred.

EXPLOITATION

At the end of the project further work was required in order to improve a number of aspects of the natural fibres/plastic compound. These include aspects of the mechanical properties, which depend on the type of binder which is used. In selecting this it is necessary to consider a number of aspects further. These include linkage problem between the fibres and the polymer as well as aspects of flammability, emission of fumes on combustion and moisture absorption.

PARTICIPANTS

Comer, Impianti Industriali (Italy)

Dan-Webforming International (Denmark).