This article explains what plywood exterior and interior grades are, how each one is made and compares the two based on a number of factors.
As the name implies, interior
grade plywood is very suitable for indoor use in homes and offices. The plywood
furniture we use in our home is actually made from this type of plywood.
Exterior quality plywood is an
excellent material and is considered ideal for outdoor use such as garden
tables and chairs that are placed outside with natural elements.
Manufacturing differences
between Exterior grade Plywood and Interior grade plywood:
Plywood is made from separate
layers (pieces of wood veneer) that are glued together using adhesives/resins. To obtain thin
pieces of wood, a separate wood veneer is obtained by rotating the logs obtained
from the trees. These pieces (veneers/plies) are then stacked one on top of
the other and glue is spread over their surface, and these veneers are
pressed together using a hot-pressure machine to form plywood sheets.
In interior grade plywood, urea-formaldehyde glue (known as UF in the industry) is used to
bond the most common types of adhesives, while in exterior grade plywood, phenol-formaldehyde (also known as phenolic
resin) is used as the best quality glue.
Strength Comparison between Exterior Grade Plywood and Interior
Grade Plywood:
External grade plywood is stronger (better glue shear
strength) compared to interior grade plywood.
Differences in Cost:
Exterior grade plywood is also known as BWR (Boiling water
resistant) plywood is costlier than interior grade plywood (which is known
as Commercial ply).
Resistance to water:
The phenolic adhesive used on
exterior plywood is actually a plastic adhesive. Phenol is a material used to
make plastics. This adhesive provides excellent water-resistant properties to
the plywood. External plywood quality tests often involve immersing the plywood
in boiling water for up to 4 hours and then taking it out to test its strength
and other properties.
For all practical purposes, this
type of plywood is considered sufficiently water-resistant, so it can be used
outdoors or in the manufacture of kitchen cabinets and more.
UF resin, on the other hand,
is not as good as phenolic resins, so the interior quality plywood can be
damaged if exposed to water. This is the reason it was used indoors (away from
the rain).
The best way to improve the
water-resistance of indoor plywood is to use decorative laminates. These laminates
are made using papers impregnated with phenolic and melamine resins, so they
have good resistance to water.
Also Read: Flexible Plywood | Standard Sizes And Thickness | Uses - Lceted
Also
Read: Teak Wood Furniture - Benefits
And Drawbacks | Lceted
Also
Read: How To Identify Good Teak Wood
For Your Furniture? - Lceted
No comments:
Post a Comment