FAIR-CT98-3919 New functional biopolymer - natural fibre - composites from agricultural resources

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Final Report Scientific Synthesis

Source: Progress Report June 2000

Consortium: The project was co-ordinated by Fraunhofer Gesellschaft zur Förderung der angewandten Forschung e.V., Munchen (Germany) and is now co-ordinated by the Institut for Verfahrenstechnik und Verpackung, Freising (Germany), in partnership with Eidgenötsische Technische Hochschule Zurich, (Switzerland), Universita' degli Studi di Bologna, Dipartimento di Chimica G Ciamician, Bologna (Italy), Organic Waste Systems NV, Gent (Belgium),Vakgroep Biochemie, Fysiologie en Microbiologie, Universiteit Gent, (Belgium), Centro Ricerche FIAT , Orbassano (Italy)

SCIENTIFIC SYNTHESIS

Introduction

The basic idea for this project was to create technical products, made from renewable resources in the form of natural fibre reinforced bio-polymers. For this project, the major source of raw materials has to be fast growing plants. Bio-degradability, on the other hand, is not a primary goal, but only valid for defined applications. The project aims to carry the experimental steps up to the production of demonstration parts. Priority was given to automotive parts due to the inherent interest of one of the partners (FIAT), although biodegradability is not a key property in this respect. A second group of demonstration parts is to be made, for which biodegradability is a key requirement.

The target configuration of the automotive parts is composite of polymeric matrix with fibre reinforcement, to be produced by the methods of injection moulding and compression moulding. Other car manufacturers still offer car parts similar to this, but made of conventional thermoplastics (Polypropylene) with flax fibres and made by pressing. So the innovation is the use of new matrices based on renewable resources and to use injection moulding and compression moulding to form these.

The target configuration of the other demonstration parts is a composite to be produced either by injection moulding or (for a later phase) by thermoforming from sheets. The main technical issue in fibre-polymer-composites is to realise a good fibre-matrix adhesion. As a result the fundamental questions concerning the project are:

• what are the physico-chemical parameters that determine the fibre-matrix bonding?
• what are the options that can influence these parameters for the expected materials and processes under economically reasonable boundary conditions?

Non chemically modified fibres are to be preferred in view of:

• scale-up to industrial size
• the relevant economical and ecological problems
• the optional biodegradability of the resulting composites

If the fibre-matrix adhesion has to be improved, surface modification of the fibres, accompanied by minimisation of chemical steps, has priority over modification of the matrix material. The evaluation of the biodegradation processes has to answer the question whether the part is degrading and under which circumstances the part degrades - important both during use and for the waste management.

Finally a Life Cycle Assessment - coupled to an economical analysis - has to compare the new materials with conventional materials both from economic and environmental considerations.

Objectives

The project has the following objectives:

• Selection of suitable fibre and matrix components based on agro-industrial resources.
• Providing chemically modified matrix materials from renewable resources.
• Optimising processing methods for the new biocomposites.
• Manufacturing demonstration parts on a pre-competitive level, with the automotive industry the main potential market.
• Characterising the new materials according to industrial standards.
• Assessing bio-stability and biodegradability of the composites
• Manufacturing parts where there is a specific need for biodegradability.
• Establishing a cradle to grave analysis with respect to the environmental and economic impacts of the processed demonstration parts.

Activities

The activities are divided into four tasks as follows:

Task 1 Natural fibres

• procurement of raw materials (hemp, flax, miscanthus, sorghum, broom, etc)
• separation, degumming
• fibrillation
• fibre fractionation
• material manufacturing
• yarn production
• textile processing
• surface modification

Task 2 Matrix materials

• procurement of PHF, PHBV, TPS/PCL, PLA
• additives, colours, fillers
• chemical modification
• reactive extrusion

Task 3 Processing of biocomposites

A. Compounding/extrusion

• short fibre reinforced injection mouldable mass
• assessment of rheological data
• reactive extrusion
• extrusion coating

B. Injection moulding

• low - high fibre content
• variation of fibre length

C. Continuous fibre reinforced composites

• textile precursors (knitting, weaving)
• impregnation process
• hot pressing (sheet moulding)
• extrusion coating

Task 4 Demonstration parts

• automobile use (car parts)
• containers, cans
• funeral articles
• extruded profiles
• earth anchors, geotextiles

During the current reporting period the objectives of the second task were modified. Reactive extrusion, as originally planned, was shown not to be an economically competitive strategy for chemical modification.

Questions of matrix/fibre-bonding were investigated on the basis of technical and economic reasons depending on the ways in which fibre modification was accomplished. Suitable fibres (flax, hemp and broom) were selected and procured. In the first year the work was focused on flax fibres. It is assumed that results regarding modification, processing and properties of the composites can to a large extent be transferred to other cellulosic fibres such as hemp. Cefor (which is a regenerated cellulose) served as reference material.

Processing steps of recovering fibres from plants were investigated, with the initial samples of fibres surface modified at a laboratory scale.

The matrix materials were selected, procured, characterised and tested. Some of these (as shown in the following table) were deselected for this project, either due to technical reasons in processing or end use properties or due to lack of availability at minimum in technical scale (some tens of kilograms).

The end materials, including blends of starch with synthetic polymers, proteins and PLA (poly lactic acid) are as follows:

Material	Ingredients	Properties / Remarks
MaterBi A105H Novamont S.p.A., Italy	Starch, Plasticiser, Cellulose derivative, EVOH-co-polymer	Commercially available, Starch is a minor component. High loss of mass even at using and processing temperature
MaterBi Y101 U Novamont S.p.A., Italy	Starch, Plasticiser, Cellulose derivative	Commercially available, Starch is a minor component. High loss of mass even at temperatures for processing and use.
Bioplast GS 902 Biotec GmbH, Germany	Starch, derivatives of Cellulose, a natural softener system, biodegradable polymers, synthetic plasticiser	Commercially available granule with many components. High loss of mass even at temperatures for processing and use.
Sconacell S Buna SOW Leuna, Germany	Acetylated Starch	No longer available.
Sconacell A Buna SOW Leuna, Germany	Acetylated Starch, Platiciser	No longer available.
*IVV derivatised pea starch	Acetylated Starch, Plasticiser	Available in small amounts, in development.
Slaughterhouse waste protein ETHZ, Switzerland	Meat Proteins + ?	Available in small amounts, Image problem
Wheat Gluten Montpellier University, France	Plant Protein + ?	Available in too small amounts.
*IVV Lupine protein	Plant Protein, Plasticiser	Available In pre- commercially amounts. In development.
PLA Brussels Biotech	PLA	Not available - first amounts in Belgium 2001.
*Lacea H 1 00-E Mitsui Toatsui Chemical Japan	PLA (+Plasticiser)	Commercially available, good co-operation.

*selected for further work

Progress

In general all tasks are on schedule. Both fibres and matrices have been selected, procured and tested. The test methods for characterisation have been evaluated. The characterisation of the raw materials and of processed materials is on going. Processing steps are being carried out. The data inventory for Life Cycle Analysis has been set-up. The Biodegradation test methods have been evaluated and the measurements started.

During the course of the project so far, some objectives had to be modified for the following reasons:

• Use of animal proteins as matrix materials - problems were anticipated in terms of the public accpetance of such materials.
• Reactive extrusion as a method for chemical modification was rejected as being economically non-competitive.

Results

Selected matrix materials, based on renewable resources were polylactic acid (PLA, semi commercial grade), blends of native starch with other polymers (in three commercial grades), starch derivatives (larger scale experimental products), and proteins (in the basic experimental scale). PLA and starch derivatives had to be plasticised in order to match the mechanical properties between fibres and matrices. Proteins could not be processed in regular thermoplastic conversion.

The natural fibre selected were flax, broom, hemp and grass (miscanthus). Physical treatments were mechanical decortication and steam explosion. Chemical modifications tested were etherification and esterification. Regenerated Cellulose fibres were used as reference.

For the production of injection moulded parts, matrix and fibres have first to be compounded to produce containing granules. For this step, fibre input into the extruder was found to be a significant technical problem. Feeding with fibres in compacted form (card, sliver) gave good results in one case. Feeding of fibres in single form using equipment developed by the project proved to give too low a level of filling.

Injection moulding was carried out in three stages:

• Mini-moulding of small test bars as an efficient way to work with small amounts of materials, Moulding of regular test bars, and
• Moulding of four different test products.

Fibre reinforced injection moulded composites were mainly made in combination of PLA and 10% to 40% of non modified and several types of chemically modified flax fibres. The fibre reinforcement led to tensile properties that were only slightly better than pure PLA. Better relative improvement could be achieved on matrices of lower tensile strength than PLA.

For compression moulding, hybrid fleeces from natural (flax) and polymeric (PLA) fibres were made, with weight fractions of the natural fibres between 30% and 65%. The compression moulded parts produced from these materials were flat sheets and one type of automotive part, as a test product. The longer fibre length achieved by this technique gave a significant increase of tensile properties over the matrix material.

Test on biodegradation in soil showed a complete biodegradability of natural polymers and fibres. PLA shows only a very slow degradation under these conditions, whether or not in combination with fibres. Under controlled composting conditions, natural fibres and PLA were completely degradable. For the two starch blends and chemically modified starch, degradation is much slower or even not detectable.

Achievements

Fibres as well as matrices were procured. The methods for modification have been worked out. First process steps were tested. Test samples, including matrix/fibre mixtures were shown to be suitable for thermoplastic processing.

Discussion

The necessary steps for finally producing several demonstration parts on a larger scale have been completed:

• Procurement of fibres and matrix materials, physical treatment of fibres.
• Plastification of matrix polymers, chemical modification of fibre surfaces
• Reinforcement of matrices with continuous fibre supply on thermoplastic processing equipment
• Production of demonstration parts at small scale.

The expected technical goals appear to be achievable. Environmental and economical comparisons with conventional parts can yet be made since the final systems have to yet to be defined. This will be done in the last project period. In particular it has been shown that the economic viability is largely depending on the requirements for treatment of the fibres.

Future Actions

The next steps have to be the up-scale of the above mentioned process steps:

• Scale-up of fibre modification to the multi kg scale
• Starch derivatisation into a scale of > 50 kg
• Compounding of PLA and derivatised starch in a scale of > 50 kg
• Compounding the matrices with the fibres into convertible granules in a scale of > 50 kg
• Production of compacted fibre fleeces, by part extrusion coated
• Production of demonstration parts in smaller scale by injection moulding, compression moulding, vacuum assisted thermoforming
• Production of automotive demonstration parts in larger scale by injection moulding and compression moulding, simulation of industrial processes
• Enhancement of lupine protein development.
• Advance the toughness of PLA.
• Find matching microbial strains for PLA.
• After definition of the large scale demonstration parts, a Life Cycle Assessment is to be performed. Characterisation of materials and the investigations concerning biodegradability are continuing tasks.