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Welcome to CP Adhesives' Blog

We will be discussing a wide variety of adhesive and wood related topics.  Check back frequently as we hope to update this daily.  If there's a topic you'd like addressed be sure to send us an e-mail.


All Things Adhesive Related


February 5, 2008
Bleed Through Prevention

Occasionally, I receive calls from manufacturers experiencing "bleed through" when laying up veneers.  Bleed through is the result of moisture in the adhesive carrying glue solids through the pores of the veneer to the surface.  This usually results in finishing problems.  Bleed through normally occurs when using porous species such as oak but can occur with any veneer.  The major cause is a heavy glue spread.  By minimizing the spread you can lessen the bleed through.  Additionally, allowing some open time after the adhesive has been applied to the substrate will result in less bleed through.  Finally, the use of a "filled" adhesive can help prevent bleed through by clogging the pores of the wood.


February 5, 2008
PVA VS. Urea Resin in Panel Manufacturing
 
A high percentage of panels are glued with urea formaldehyde resin and because it is a thermosetting, non-reversible adhesive it has no practical limitation on heat resistance.  In other words, urea formaldehyde resin glue lines will not soften at any temperature.  A small proportion of your panels are glued with polyvinyl acetate adhesives (PVA) and this glue line will begin to soften at around 160F with danger of bond failure at 200F plus or minus 10 degrees.  This is normal for all PVA whether cross linking or not, and there really is no way this can be significantly increased.  However, it should be understood that glueline softening is also a function of time and glue line depth as well as temperature. In a finishing operation the time under a high temperature of perhaps 300F,  probably will not be long enough to significantly soften a PVA glue line, especially given that your panels will have 3/4 inch of glue line and the depth of heat penetration will be quite small even with exposure of a minute or two. 



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