Lightweight particleboards made from annual and perennial plants or based on foamed adhesives
The objective of two projects carried out by Fraunhofer WKI as well as research and industrial partners is to develop lightweight particleboards (target density varying from 300 kg/m³ to 500 kg/m³) for the furniture industry. The first project is a joint European project called DIPP (Development of Innovative Particleboard Panels for a better mechanical Performance and a lower environmental impact) in which lightweight particleboards made from annual and perennial plants such as hemp, sunflower, topinambur, maize and miscanthus are produced. As the stalks of sunflower (Helianthus annuus), topinambur (Helianthus tuberosus) and maize (Zea maize) are filled with light parenchyma cells, they are particularly suitable for the production of lightweight particleboards. Different conventional and natural adhesives like urea- or tannin-formaldehyde resin and PMDI were used, and the properties of the boards produced were compared with reference particleboards made from wood particles. In the second project, funded by the German Ministry for Education and Research (BMBF), a lightweight particleboard based on foamed adhesives is developed. Within this project, three strategies are pursued: · Foaming of urea-formaldehyde adhesive using air and surfactants; · Mixing of expandable, gas-filled microspheres and polystyrene into UF adhesive; · Use of formaldehyde-free, foam-generating polyurethane adhesives. Physical and mechanical properties of particleboards were tested and presented in detail at the symposium.