Three Adhesive Recipes Based on Magnesium Lignosulfonate, Used to Manufacture Particleboards with Low Formaldehyde Emissions and Good Mechanical Properties

Adhesives represent an important part in the wood-based composite production, and taking into account their impact on the environment and human health, it is a challenge to find suitable natural adhesives. Starting from the current concerns of finding bio-adhesives, this paper aims to use magnesium lignosulfonate in three adhesive recipes for particleboard manufacturing. First, the adhesive recipes were established, using oxygenated water to oxidize magnesium lignosulfonate (Recipe 1) and adding 3% polymeric diphenylmethane diisocyanate (pMDI) crosslinker (Recipe 2) and a mixture of 2% polymeric diphenylmethane diisocyanate with 15% glucose (Recipe 3). The particleboard manufacturing technology included operations for sorting particles and adhesive recipes, pressing the mats, and testing the mechanical strengths and formaldehyde emissions. The standardized testing methodology for formaldehyde emissions used in the research was the method of gas analysis. Tests to determine the resistance to static bending and internal cohesion for all types of boards and recipes were also conducted. The average values of static bending strengths of 0.1 N/mm(2), 0.38 N/mm(2), and 0.41 N/mm(2) were obtained for the particleboard manufacturing with the three adhesive recipes and were compared with the minimal value of 0.35 N/mm(2) required by the European standard in the field. Measuring the formaldehyde emissions, it was found that the three manufacturing recipes fell into emission classes E1 and E0. Recipes 2 and 3 were associated with good mechanical performances of particleboards, situated in the required limits of the European standards. As a main conclusion of the paper, it can be stated that the particleboards made with magnesium-lignosulphonate-based adhesive, with or without crosslinkers, can provide low formaldehyde emissions and also good mechanical strengths when crosslinkers such as pMDI and glucose are added. In this way magnesium lignosulfonate is really proving to be a good bio-adhesive.