Canadian Plywood:
Why is it so Tough, Durable
and Reliable?
Plywood is the Original Engineered Wood Product
Plywood's cross-laminated construction capitalizes on the more desirable physical and mechanical properties of wood.
Benefits include:
- Superior dimensional stability
- Exceptional two-way strength
- Highly resistant to damage from impact
Plywood is engineered to be stronger...Naturally.
Glue Bond History
Canadian plywood was first manufactured in British Columbia in 1913, but
it was not until the 1930's that the discovery of a waterproof glue, that
the story of modern plywood really began.
Dr. Leo H. Baekeland, discovered that a mixture of phenol (carbolic acid), formaldehyde and alkali under controlled heat produced a synthetic resin with amazing properties!
Not only could it be moulded into any shape (like a telephone), it could also be used as a tough waterproof adhesive.
This is because the alkali acted as a catalyst, causing the phenol and formaldehyde to undergo remarkable chemical changes when heated. The molecules of these two chemicals combine to form a new compound - phenol formaldehyde.
3 Stages of Chemical Reaction:
A Stage
During the first reaction stage, the molecules of the newly-formed resin
compound can be dissolved with water.
B Stage
As more heat is applied molecules combine to form still larger molecules.
C Stage
The compound is no longer affected by water and can still be dissloved
by alcohol, but as still more heat is applied.
The molecules are fully developed because all their chemical combining capacity has been used. Chemists now say the material has polymerised - meaning "set" or "cured" There is now no way to break the molecular links or bond.
Hot press bonding of plywood with this new glue, a phenol formaldehyde resin, sparked a technological revolution in the manufacture and use of plywood. A new world of exterior applications opened up for plywood because of its waterproof glueline. A glueline unaffected by extremes of moisture, heat or cold.
Today this same phenol formaldehyde adhesive is used to bond together individual plies, forming waterpoofed-glued CANPLY plywood!
Read the Tech Note about our permanent, waterproof gluebond TN02-2003.
Plywood Technical Data
Plywood Engineering Properties and Design Values
The Plywood Manufacturing Process
| Step 1 : Log Processing | |||
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The log emerges from the barker after having been stripped of its bark. | ||
| Step 2 : Log Conditioning | |||
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The logs are conditioned using steam or hot water to improve peel quality. | ||
| Step 3 : Lathing | |||
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At the lathe, a sharp blade peels the log, now called a block, into a continuous sheet of veneer. | ||
| Step 4 : Veneer Application | |||
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Green veneer is dried in steam or gas heated ovens. | ||
| Step 5 : Veneer Coating | |||
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Veneers are coated with waterproof glue and laid up into sandwiches. | ||
| Step 6 : Curing | |||
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The veneer sandwiches are subjected to heat and pressure in the hot press until the glue is cured. | ||
| Step 7 : Grade Selection | |||
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After pressing, the plywood panels are trimmed, squared and selected for grade. | ||
| Step 8 : Inspection | |||
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Finished plywood panels are carefully inspected and graded. | ||
| Step 9 : Quality Control | |||
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CANPLY Quality Control inspectors check finished plywood panels in inventory. | ||
| Step 10 : CANPLY Testing | |||
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Plywood samples, selected at random, are tested in CANPLY's laboratory. | ||
| Step 11 : Boiling Tests | |||
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Other samples are subjected to the boiling test specified by the CSA. | ||
| Step 12 : Pressure Tests | |||
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Some samples are subjected to vacuum-pressure tests. | ||
| Step 13 : Shear Tests | |||
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Samples are shear tested to determine the strength of the glue bond. | ||
| Step 14 : Test Results are Compiled and Reports are Circulated |
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The CANPLY "Mark of Excellence" is an assurance to consumers that our plywood meets the high quality standards established by the industry and that it will perform in a satisfactory and predictable manner. Only plywood manufactured by member companies of CANPLY are licensed to use this stamp.
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| More
information on the plywood manufacturing process is available through
our "On-line Seminars" in the Literature & Media
section (click here). |
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