The influence of plasma treatment on the bonding of European beech (Fagus sylvatica L.) and Norway spruce (Picea abies Karst.) wood with a melamine-urea-formaldehyde (MUF) adhesive was investigated. Twelve three-layer beams were made: four of beech, four of spruce, and four hybrid, with the outer lamellae made of beech and the inner one of spruce. Half of the lamellae were plasma treated before gluing, the other half were not. It was found that plasma treatment did not significantly affect the shear strength of adhesive joints. Both control and plasma-treated specimens exhibited similar shear strength within each type of glulam beam (beech, spruce, and hybrid), and in most cases there was 100% wood failure. In two delamination test methods according to standard EN 14080 (B and C), a difference in the degree of delamination was observed between the control and plasma-treated beech specimens, where plasma treatment of the lamellae surfaces prior to bonding improved adhesion with MUF adhesive.
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