HyLight:
Energy-efficient production of complexly shaped, multifunctional and recyclable lightweight-construction products made from wood and bioplastics by means of automated molding machines

Project start / October 01, 2022

Hybrid lightweight-construction materials made from renewable raw resources are increasingly gaining importance on the market. With such materials, resource- and climate-friendly products can be manufactured that fulfill several functions - for example, load-bearing construction products with integrated thermal and sound insulation as well as durable (upholstered) furniture and packaging. Efficient component geometries enable substantial weight savings with simultaneous high mechanical stability. In collaboration with research and industry partners, we are developing a process for the manufacture of complexly shaped products made from wood or agricultural materials and bioplastics by means of automated molding machines. One important component of the material and technology development is furthermore the highest possible material recyclability of the products after the end of the first period of use.

Last modified: October 01, 2022

The photo shows a cuboid body consisting of an airy but stable mixture of wood shavings of varying sizes. — © Fraunhofer WKI
Preliminary tests have already been promising: By means of steam bursts, high-performance lightweight materials can be produced from wood or agricultural residues and bioplastics in a single process step (example here: molded body made from pine chips and melted-on bio PA fibers).

The microscope image shows wood fibers bonded together by a whitish-transparent, crystal-like mass. — © Fraunhofer WKI
Thanks to the molecular bond between pine chips and bio PA fibers, adhesives and bonding agents can be omitted.

Wood is a good lightweight-construction material. By nature, it has a low bulk density and high stability. The tensile strength in the direction of the fibers (in relation to the bulk density) is greater than that of steel. Compared to modern lightweight-construction materials such as fiber-reinforced PU foams or plastics (CFRP/GFRP), wood-based materials are, however, often still relatively heavy when the mechanical requirements are fulfilled. Or they are light and possess good heat-insulating properties, but are mechanically less resilient.

Project goal: Materials, components and manufacturing process

This is where the project idea comes into play: Bio-based polymer fibers (“bioplastics”) or particle foams are to be combined with wood (plus agricultural residues such as straw, husks, etc., or paludi biomass) and processed to form extremely lightweight, stable components by means of an automated molding machine.

Two approaches are thereby being pursued:

The development of hybrid materials from particulate raw materials such as wood fibers or chips and polymer fibers or foam beads
The development of reinforced hybrid materials: Particle foam or particle/particle hybrids with inserted reinforcing component (e.g. veneers, square timber, wood-based material) and/or with cover layers (e.g. molded veneer, fabric, films)

Until now, automated molding machines have been used exclusively for particle-foam processing. More precisely, pre-expanded thermoplastic polymer beads are bonded to the finished molded part within a very short time (a few seconds) using a short burst of hot steam or by means of energy from electro-magnetic waves (HF technology). Within the framework of the project, this technology will be used in order to develop a new processing technology (bonding and pressing) for novel bio-hybrid materials.

The polymer particles thereby act as an adhesive. Bioplastics with low melting points (< 130 °C) are particularly well suited for the project. In the molding machine, an astonishingly good adhesion between the surface-melted polymer and the wood or agricultural residue is created through the application of a very short, hot burst of steam, or energy in the form of electro-magnetic waves. The focus in this project is directed in particular at commercially available, bio-based polylactides (PLA) and polyamides (PA).

Planned technology demonstrators fpr the following application areas:

Thermal insulation of buildings: molding machine and insulation element in commercial format
Furniture construction: molding machine and furniture element

Recycling

Recycling possibilities and recycling potentials should be incorporated into the development from the outset (design for recycling). The recycling of PLA, for example, is not yet economical and is still in its infancy. Possible recycling concepts and advantages are therefore to be investigated.

Tasks of the Fraunhofer WKI

The primary tasks of the Fraunhofer WKI in the project (in addition to the coordination of the joint project) are:

Production and supply of wood particles
Investigation of various lignocellulosic materials and bioplastics with regard to bonding ability/adhesion to one another
Handling and mixing of wood fibers and other lignocellulose-based particles with polymer fibers
Production of reinforcing components for the manufacture of hybrid molded parts for furniture construction
Characterization of hybrid materials for the application areas of thermal insulation and furniture construction
Investigation of recyclability:
- Production of wood-based materials such as particle board or MDF using the shredded hybrid material
- Tests on the separability of the components

For lightweight-construction applications with stringent mechanical requirements and, at the same time, good heat-insulating properties, petrochemical-based products have been primarily used up to now - for example, fiber-reinforced PU foams. In order to change this, we are developing a universal bio-based material and processing concept with adjustable properties for the industrial manufacture of diverse products (large-scale production).

Lightweight wood-based materials could then be produced with short cycle times (in the range of seconds) in any complex – even undercut – three-dimensional geometry and with a variety of surfaces. Such an efficient production technology has not yet been available for the manufacture of wood-based materials.

With this project, we are providing a contribution towards environmental and climate protection, and are enhancing Germany as a business location:

Outstanding eco-balance of the products:
- CO₂-neutral, renewable and, in many places, regionally available raw materials
- Utilization of wood sources that are underutilized or of inferior wood quality, such as wood from thinning and landscape management, as well as agricultural residues
- Low raw-material input
- No additional adhesive or bonding agent required
- Low transport energy for raw material and product transport due to short transport distances and low weight
- High-quality recyclability with materially usable end products
Safeguarding of existing jobs and creation of new jobs in Germany:
- Utilization of domestic agricultural and forestry products
- The process should be easy to integrate into existing industrial processes without significant effort or cost, and is even suitable for decentralized manufacturing.

Furthermore, natural insulation materials offer technical advantages for the users:

Pleasant living climate: good compensation for fluctuations in temperature and humidity, improvement in summer heat protection
Good sound insulation
Low to no pollutant load: suitable for applications in indoor areas

Economic advantages

Upon successful completion of the project, a process solution will be available for the energy-efficient, large-scale production of bio-based, multifunctional molded parts for lightweight-construction applications in the construction industry and for furniture manufacture. Furthermore, the technology could also be of interest to the automotive industry - for example in the production of lightweight, crash-resistant vehicle parts with simultaneous thermal protection and/or sound insulation.

Diverse companies are thereby provided with a further possibility for improving the eco-balance and, consequently, the competitiveness of their products. At the same time, the extremely light construction and the utilization of raw materials available regionally or throughout Europe could have a positive impact on supply chains and manufacturing costs:

Greater independence from foreign raw-material suppliers
Low logistics costs
Very low material input
Low-cost, permanently available raw materials
Decentralized production possible

Automated molding machines are modified in such a way that the hybrid materials described are produced according to the same principle as particle-foam materials. In an ideal case, the required plant modification is even possible on existing equipment (for EPS or EPP). In this case, the outlay for implementation in current industrial plants and processes would be very low.

The envisaged manufacturing technology offers promising potential with regard to the realization of the multifunctionality and flexibility required by users at a simultaneously low cost:

Extremely fast production
Elimination of the process step “bonding” due to adhesive-free molecular-based bonding between wood and bioplastic
Enhancement of mechanical properties such as higher bending and shear strength through fiber-oriented inserts and coatings
Stable connection points made from bio-based inserts, for attaching fasteners such as screws
Customized environmentally-friendly special solutions in terms of shape, weight and stability (complex, material-efficient geometries)

Project partners

Joint project coordination: Fraunhofer WKI
University of Göttingen | Institute for Wood Biology and Wood Technology
Kurtz GmbH
Innolation GmbH
Sto SE & Co. KGaA
Wilkhahn Wilkening+Hahne GmbH+Co.KG

Funding

Official project title: Verbundvorhaben: Formteilautomaten zur energieeffizienten Herstellung komplex geformter, leichter Holzprodukte
(Joint project: Automated molding machines for the energy-efficient production of complex-shaped, lightweight wooden products)

Sub-project 1 (Fraunhofer WKI): Mischung, Verklebung und Prüfung verschiedenster Hybridwerkstoffe
(Mixing, bonding and testing of widely differing hybrid materials)
Sub-project 2 (Georg-August-Universität Göttingen): Funktionalisierung und Optimierung der Hybridwerkstoffe
(Functionalization and optimization of hybrid materials)
Sub-project 3 (Kurtz GmbH): Entwicklung und Bau eines Formteilautomaten zur Herstellung von Bauteilen aus nachwachsenden Rohstoffen
(Development and construction of an automatic molding machine for the production of components from renewable raw materials)
Sub-project 4 (Sto SE & Co. KGaA): Verwendung der projektspezifischen leichten Holzprodukte als Fassadendämmung z. B. in Wärmedämm-Verbundsystemen
(Use of the project-specific lightweight wood products as facade insulation, e.g. in external thermal insulation composite systems ETICS)

Funding body: German Federal Ministry of Food and Agriculture (BMEL)

Project management: Fachagentur Nachwachsende Rohstoffe e. V. (FNR)

Funding reference: 2220HV041A, 2220HV041B, 2220HV041C, 2220HV041D

Duration: 1.10.2022 to 30.9.2025