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New Classes of Engineering Composite Materials from Renewable Resources

Final Report Summary - BIOCOMP (New Classes of Engineering Composite Materials from Renewable Resources)

The project aimed at new high quality bio-based composite materials to substitute synthetic plastics and wood. These materials in development should deliver a breakthrough in properties and use of engineering biocomposites. They comprise both, thermoplastic and thermoset materials derived mainly from renewable, natural resources composed of biopolymers and reinforcing natural fibers.

The project focused on biomass extracts to be directly used in engineering plastics or wood like materials applying only minimal modifications and including only additives from natural resources.

The approach of the Integrated Project BIOCOMP included the development of thermoplastics and thermosets based on available biopolymers or precursors with the potential to achieve the challenging objectives. The reinforcing natural fibres were those available in Europe. Advanced methods of control, simulation and processing supported the development. Prototypes and demonstrators showed the performance of the materials in end-use applications.

The activities, processing and materials within the project comprised:
- Biopolymers
- Natural fibres
- Fibre improvement
- Natural or eco-friendly additives
- Design / simulation
- Demonstrators.

All materials experienced a strong technical progress within BIOCOMP with a target to achieve properties competitive to synthetic plastics. A life cycle analysis could demonstrate substantial advantages above the synthetic counterparts.

The thermoplastic biopolymers lignin, starch, PLA and PHB were established as engineering composites for parts used in many commodities for various industrial branches. Impact modified materials developed with innovative methods of long fibre direct processing (LFT-D) could surpass the challenging target of the project, an impact strength of 50 kJ/m2. Cellulose regenerated fibres increase impact strength without reduction of tensile properties of PLA composites. These materials can compete with ABS (AcrylonitrileButadieneStyrene) and HIPS (high impact polystyrene) often used for housings of equipment of electronics and automotive interior panels.

The furan resins could be established as a new thermoset material for industrial applications to be processed by most standard methods of low cost and mass production of thermosets. Processing included: compression moulding, vacuum infusion, hand lay-up, BMC (Bulk moulding compound), SMC (Sheet moulding compound) and RTM (Resin transfer moulding).

Demonstrators or model products are semi-finished or finished devices of a prototype character that show the benefits of the developed materials but also their drawbacks, be it in manufacturing costs, time, surface finish, structural performance, acoustics etc.

Exhibiting wood-like properties, lignin formulations can be processed like a thermoplastic material. It shows the potential for manufacturing industrially relevant products. The mechanical properties of the material depend on the fibre content. The material developed in the project, experienced a substantial progress of the impact strength to enable applications similar to those of polypropylene / talcum and of low quality polyamides. The excellent acoustic properties proved by dynamical frequency dependent testing predestinated this material for loudspeaker housings. A mould was designed and constructed to manufacture such covers in a single step. Without sink-marks in the 1cm thick shell of a 250 mm diameter, a perfect dimensional stability resulted from the trials.

The hydrophilicity of the starch is a major barrier to prevent its large scale industrial use. However this was reduced in BIOCOMP by crosslinking of the native starch hydroxyl functionalities and substitution of the hydroxyl functionalities with for example acetyl groups.

Polylactide (PLA) is a biodegradable, aliphatic polymer, which can be obtained from renewable resources by fermentation and is mainly used in medical applications. Natural fibre filled PLA compounds show enhanced mechanical properties e.g. stiffness, but toughness needs to be increased. Impact modification solutions gained in BIOCOMP enable engineering applications with good mechanical properties Approaches to modelling the mechanical behaviour were successful, enabling structural and flow field simulations.

BIOCOMP initiated the use of innovative processing methods to manufacture materials and semi-finished parts. A process, very cost effective and reducing thermal loads to the components, is the long fibre technology by direct processing and in-line compounding (LFT-D-ILC), which is applied for glass fibre reinforced thermoplastics in industry. This method was modified to develop a demonstrator - a foot rest fitting for a car comparing all basic fibre types hemp, flax and wood together with PLA and impact.

Dispersion of the fibres in the matrix and reduction of thermal loads to the composite constituents are crucial issues for high quality BIOCOMP materials. A planet extruder with 1 centre screw and e.g. eight planet screws around the centre screw meets these requirements and provides a homogeneous fibre dispersion / distribution, a very good degassing and 'soft' compounding conditions.

PLA matrix composites can also be extruded in a similar way like wood plastic composites WPC (with synthetic polypropylene). Five Biocomp materials were extruded to profiles with a Conical Twin Screw Extruder
- Cincinnati T58 fiberex with the compositions of PLA 30%
- Hemp and impact modifier, PLA 50%
- Flax, TPS (thermoplastic acetylated starch) 50%
- Hemp, PLA 30%
- Wood and PLA 50%
- Wood.

Vacuum consolidation and press moulding of PLA film stacked with various natural fibre materials included non-woven flax, woven hemp and unidirectional flax fabrics. For vacuum consolidation, the PLA film and natural fibre materials were stacked alternately to obtain the desired thickness and percentage fibre, placed on an aluminium tooling plate, covered with release film, breather cloth and a vacuum bag, which was sealed with sealant tape.

For thermoset materials furan resins and plant oil resins were selected from various polymers. The potential of the furan to achieve properties of synthetic thermoset composites was estimated to be high with benefits of high thermal and chemical stability, whereas as the crops oil derivatives would be free of formaldehyde.

Evaluating BIOCOMP, Live Cycle Assessment (LCI/LCA) focused onto resin processing, the energy consumption and effects to the climate change as well as on further materials and additional impact categories. It used BIOCOMP processing results as summarized in the chapters above, mainly for PLA, furan and lignin based composites, respectively.

The following aspects of natural fibres and matrices regarding the sustainability were identified:
- Hemp seems to be the better alternative compared to flax with regard to pesticide use for weed control and agricultural benefits.
- Flax produces fibres and seed (sowing, oil extraction, animal feed).
- Dessication with Glyphosate may be adopted in certain cases for hemp (baby-hemp approach) and flax. (Glyphosate is though frequently used e.g. in corn production (PLA), but according to the literature the pure substance is much less ecotoxic than other pesticides- though effects are found for formulations). Nevertheless, the industrial quality of the fibres resulting from that process is diverting very much being presumably not the best methodology for high quality industrial grade fibre production.
- Comparing different retting scenarios hemp and flax have about the same impact.
- Furfural the precursor of furan resins is processed from a variety of agricultural waste products.
- Overall LCA score for processing furan oligomers is dominated by the emissions from old-fashioned primary process equipment 'own by Quaker Oats' and 'Chinese method' - new approaches promise substantial improvement.
- Lignin is produced also from 'waste' products coming from pulp industries or bio-ethanol processing. The overall score is better than for crude oil based matrix materials.
- PLA biotechnological production avoids highly toxic educts (hydrogen cyanide).
- PLA: Gen modification may improve the sustainability of PLA production.

BIOCOMP made a substantial progress in the development of materials from renewable resources and their knowledge-based processing. Manufactured and tested demonstrators could reveal the quality of the materials, the data of selected formulations are available in data bases.

All four thermoplastic matrices with natural fibres can be processed to plastic or wood-like materials and parts of engineering quality for industrial mass production. The materials demonstrated technical advantages and can compete with synthetic plastics.

BIOCOMP materials use components completely or predominantly of biomass constituents together with natural fibres, partially from existing extraction processes like lignin and furans. Considering all investigated polymer matrices polylactide, starch, lignin, furan and crops oil based resins, the BIOCOMP composites could be processed using standard methods of plastic mass production. In addition, advanced processes like LFT-D of composite industries work also for BIOCOMP materials. This advantage enables a short or medium term commercialization. A substantial progress of the material development could be achieved towards properties of competing synthetic plastic composites and demonstrated by products manufactured under industrial condition. Extensive testing proved that the properties could be comparable to normally used synthetic polymer composites e.g. the mechanical properties. Unique materials in the world evolved from the project like the lignin and furan resin matrix composites.