Various types of Plywoods and their Usages
Plywood is one of the important building material , being used all over the world. Plywood can be used for both exterior and interior purposes. Before going into detail, we must know , What is plywood?
Plywood is thin form wood joined together by means of external bonding material called glue. In other words , thin layers of wood placed in a balanced way to create a plywood. The construction of plywood is always in odd number, to make it balanced way.
Since olden days , thin form of wood , joined together , with natural clay to starch to synthetic resins.
Various types of Plywood
Plywood is classified into two major types. One is Interior Grade Plywood and another one is Exterior Grade Plywood. All types of Plywood grades are based on the bonding material being used. All the exterior grade plywood can be used for external and internal purposes. But Internal grade is not recommended for exterior purposes.Depends on grade the price of the material may vary. But the price should not mislead you , while going for plywood purchase. To be precise, it is advisable to know , where we are going to use the plywood. And get the recommendations from the supplier and manufacturers.
As such , Depends on the grade the testing methods of national standards and international standards may vary. Understanding these things and opting for the right grade is important.Buying external grade one for internal purposes , will be costlier and opting internal grade for external grade will lead frequent change of plywood panel and also costlier affair.
How the Plywood Grades are Differentiated
As Explained above plywood grades are based on the bonding material used. There are two types of glue commonly used for making the plywood.One is thermo plastic type and another one is thermo - set type .
The thermo-plastic type glue used as bonding material the plywood can be exploited for internal grade only, due to the inferior quality of the bonding materials. Some of the thermo-set glue also resulting in inferior bonding quality, due to its characteristics.
The thermo-set type glue used as bonding material , the plywood can be used for external purposes.
Basically , when we talk about the inferior quality, we talk about the water resistant property of the bonding material and it imparts the same to the plywood, when it is subject to exterior purposes. Various test methods are used to determine the water resistance for external grade plywood.
This is applicable , from 3 to 4mm to 18 to 25mm of thickness of plywood. So there is no such thing that , only thinner plywood or thicker plywood can be made as exterior grade.
Exterior grade plywoods
The following grades of plywood called as exterior grade plywood and used for exterior purposes.
1. Marine grade.
2. Boiling water proof grade.
3. Phenolic resin bonded.
4. Tannin based glue used .
5. Resorcinol based glue used.
6. Combination of Phenolic to other glue used.
Interior grade plywood
1. Pvac glue based .
2. Urea formaldehyde glue based.
3. Starch based glue.
4. Casein based glue.