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Title: The impact of log heating on veneer quality and plywood performance

Source: In: Proceedings, international scientific conference on hardwood processing. Lathi, Finland: 184-190.

Author(s)Rohumaa, Anti; Hunt, Christopher G.; Frihart, Charles R.; Kers, Jaan; Denaud, Louis; Hughes, Mark

Publication Year: 2017  View PDF »

Category: Conference Proceedings
Associated Research Project(s):   FPL-4707-1B

Abstract: In veneer-based products manufacture, logs are commonly heated to soften the wood material prior to peeling. At a higher heating temperature, veneer properties like lathe checking and surface roughness generally decrease, but the literature has shown no clear effect of these changes on bond quality. One of the reasons could be that the evaluation methods used for roughness are not able to detect the depth of lathe checks or the integrity of the surface, which probably have a significant effect on bonding quality. In the present study silver birch (Betula pendula Roth) logs were used to prepare the veneer and a liquid phenol-formaldehyde (PF) resin was used in the bonding process. Lathe check depth, surface roughness, surface integrity and plywood bond strength were evaluated. This study indicated that the heating of the logs not only softened the wood during peeling, but also causes irreversible changes in the wood material which subsequently effects plywood bond strength development. During plywood bond testing according to SFS-EN 314, deep lathe checks in veneer significantly reduced the shear strength of PF bonded plywood, even though these checks are not mentioned in the standard. These findings not only confirm the importance of minimizing the depth of lathe checks for product quality, but also demonstrate how check depth could influence a test (SFS-EN 314) which was designed mainly for testing adhesive properties and evaluate adhesive cure.

Keywords: Lathe checks; veneer; plywood; bond strength; roughness

Publication Review Process: Non-Refereed (Other)

File size: 745 kb(s)

Date posted: 10/05/2017
RITS Product ID: 88091
Current FPL Scientists associated with this product (listed alphabetically)
Frihart, Charles R.
Research Chemist
Hunt, Christopher G.
Research Chemist
 

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