Joint project: Sustainable utilisation potentials for pine heartwood
Subprojects 5 and 6: Identification and development of products
The "KiefernStolz" project, which is funded by the Agency for Renewable Resources (Facha-gentur Nachwachsende Rohstoffe e.V., FNR) within the framework of the Forest Climate Fund, is a joint project of the Fraunhofer Institute for Wood Research (WKI), Northwest German Forest Research Institute (NW-FVA) and the Georg-August-University of Goettingen. The aim is to make sustainable and efficient use of the increasing proportion of higher-quality pine logs in the future and to fully exploit the potential of pine wood as a raw material. With this in mind, new processing techniques and possible applications for the use of pine logs are to be developed and validated.
The Scots pine (Pinus sylvestris, L.) is one of the most important tree species in Germany, especially in north-eastern Germany, in terms of the proportion of forested land. Inventory data for pine show an increase in the supply of high-grade pine timber in the coming decades. This results in the demand for the development of new technical fields of application and concepts for their end use.
The focus of the project is on the development of high-quality sawn products and multilayer composites based on pine heartwood. The investigations concentrate on an inventory, the elaboration and development of new utilisation strategies for pine heartwood as well as on the consideration and optimisation of influencing parameters during the manufacturing process of the identified pine products.
Subproject 5: Bondability of veneer-based composites based on pine heartwood - Devel-opment of a 1-component adhesive system based on MDI prepolymers and special urethane polymers, respectively.
Against this background, this sub-project deals with the development of a 1-component adhe-sive system based on MDI prepolymers or special urethane polymers. Compared to PF, MUF or epoxy resin adhesives, MDI-based adhesives show a higher reactivity and a lower wetting angle, which allows a faster penetration and curing of the adhesive and consequently shorter pressing times. Further advantages of MDI-based adhesives are the higher bond strength and the lower brittleness of the bonded joint. Moreover, there is no need to worry about permanent formaldehyde emissions during use. MDI-based adhesives, however, tend to "overpentrate" the adhesive due to their greater penetration into the wood surface, which can result in "starved" glue joints.
The aim of the project is to develop an adhesive system based on MDI prepolymers, which is adapted to the specific wood properties of pine wood and can be adapted for permanent use under the knowledge of optimal manufacturing parameters. In this context, important controllable process parameters are to be investigated and evaluated. With regard to the pine wood used, the influence of growth characteristics and peeling cracks as well as the influence of heartwood and sapwood veneers on bonding will be investigated. In a further step, the use of metallic substrates and the incorporation of organic as well as mineral reinforcing fibres into the wood layer composite will be carried out so that the resulting synergy effects can be demonstrated and better understood. Based on this, a modification of the substrate surfaces by means of primers will be tested in order to achieve a higher adhesive strength between adhesive and substrate surface. It is of central importance that the manufactured materials/components show statistically validated properties in order to be able to establish the de-velopment of innovative products on the basis of pine wood on the market.
Subproject 6: Identification and development of products from pine heartwood
This subproject is divided into the work packages solid wood products and veneer based products. In the work package for solid wood products, the material quality of pine heartwood is determined and information on the processing possibilities in the currently operating pine sawmills is collected. The main focus is on the identification of products made from pine heartwood, new sales markets and property tests. The focus is on products that are made possible by the large diameters and partly intensive silvicultural treatment of pine. Among other things, it will be examined whether the strong pines can be divided into pure sapwood and heartwood assortments for different products and applications (such as windows, doors, fa-cades, decking, timber construction products, modified wood products). Furthermore, the suitability of different wood modification systems for pine will be tested. This work package is being carried out in close cooperation with the Northwest German Forest Research Institute (NW-FVA), the Department of Forest Economics at the University of Goettingen and with the support of the German Sawmill and Timber Industry Association (DeSH).
The work package for veneer based products provides for property tests on modified and bonded veneers in order to establish a property profile for the later applications of veneer products based on pine heartwood. In addition, industrial production processes will be tested within this framework. The veneer based products are produced and tested in cooperation with the Fraunhofer Institute for Wood Research (WKI).