Unit 2B: PLYWOOD

Objectives By the end of this lesson, students must be able to: • understand types of plywood • understand plywood uses and applications • describe the methods of manufacturing plywood • describe the advantages of using plywood for work • describe the limitations of the use of plywood

LESSON: TWO B

TOPIC: PLYWOOD

Objectives
By the end of this lesson, students must be able to:
• understand types of plywood
• understand plywood uses and applications
• describe the methods of manufacturing plywood
• describe the advantages of using plywood for work
• describe the limitations of the use of plywood

Practice Questions
1. Describe 5 types of plywood
2. Explain the steps involved in the manufacture of plywood
3. Explain 5 uses and applications of plywood
4. Describe 4 advantages of using plywood for work
5. Describe 3 limitations of the use of plywood

Plywood (Author – Shanta Urmila Mou)
What is Plywood?

Plywood is an engineered wood sheet material made up of fine layers or flimsy strands of wood veneers attached together placing wood grains 90 degrees to one another. It is one type of manufactured board which can be described as a mixture of Medium Density Fibreboard (MDF) and Chip Board (Particle Board). It is a complex material and attaches resin and fiber sheets of wood.
Plywood has become popular through this decade because it’s relatively low moisture content which makes various tasks easy to perform with this. Mostly for outdoor uses plywood has become very important to use. The renowned British powerboatcompany uses plywood for the construction of Motor Torpedo Boats and Motor Gun Boats.

Types of Plywood
Following are the different types of Plywood.
• Softwood Plywood
• Hardwood Plywood
• Tropical Plywood
• Aircraft Plywood
• Decorative Plywood
• Flexible Plywood
• Marine Plywood
A brief description of these types of plywood is given below
Softwood Plywood
Softwood Plywood which is also known as spruce-pine-fir or SPF because it’s from spruce, pine, and fir. Though it can be made from cedar (Cedrus sp), douglas fir (Pseudotsugan menziesii). If made from spruce (Picea sp) the prominent grains are coated by a system so that this kind of plywood becomes more effective as hard as concrete and used for shuttering strands and construction.
Read More: What is Softwood Plywood? Uses of Softwood Plywood

Hardwood Plywood
Hardwood Plywood is made from angiosperms. This type of plywood is identified by its firmness, hardness on surface, inflexibility, resistance quality. This can be used to bear heavy weight.
Read More: What is Hardwood Plywood? Uses of Hardwood Plywood

Tropical Plywood
Different types of timbers of tropical area are mixed to make this type of plywood. Though previously it was only collected from the Asian region, now also from Africa and America it is collected. Tropical plywood popular for some special qualities like
• Strength
• Density
• Evenness
• Inflexibility
• Resistance quality
• Thickness
South Asia being tropical region manufactures plywood most. Countries like Japan, Thailand, Taiwan, Korea, Dubai and even in America, England this type is used. The bad impact of this type is that for extreme production of this type deforestration is becoming a great problem to some countries like Malaysia, Philippines, Indonesia because these countries export plywood worldwide. Especially Malaysian plywood is known as Malaysian board in Bangladesh and huge popular among Bangladeshies because of its higher thickness.
Read More: What is Tropical Plywood? Uses of Tropical Plywood
Aircraft Plywood
Woods from Mahogany (Swietenia Macrophylla), Spruce (Picea sp.), Birch (Betula sp.) are used to make Aircraft Plywood. The African mahogany gives usable structural aircraft plywood. Among birch trees European birch is good. This type is famous for strength. This type is also made from Mahogany, Spruce, Birch but the special quality is that this is resistant to heat.
Read More: What is Aircraft Plywood? Uses of Aircraft Plywood

Decorative Plywood
Decorative plywood is also called overlaid plywood. Usually made from woods of ash ( Fraxinus sp), oak (Quercus sp.), Red oak (Quercus rubra), birch, Maple (Acer sp), mahogany, Philippine mahogany also called seraya, rosewood ( Dalbergia sisso).

Flexible Plywood
As the name goes Flexible Plywood is used for making flexible furniture or structures. The furniture of eighteen century were mostly of curved structures. These are made from Baltic Birch (Betula sp).
Read More: What is Flexible Plywood? Uses of Flexible Plywood

Marine Plywood
The type of plywood which can be used in moisture, humid, wet environment is called marine plywood. Even it can be used in moisture for long period. The layers of marine plywood bear too small core gap to feel that doesn’t permit the wood to fix water inside the gaps. It is also fungal resistant.

Plywood Uses and Applications
Plywood is an engineered wood sheet material made up of fine layers or flimsy strands of wood veneers attached together placing wood grains 90 degrees to one another. It is one type of manufactured board which can be described as a mixture of Medium Density Fibreboard (MDF) and Chip Board (Particle Board). It is a complex material and attaches resin and fiber sheets of wood.
Followings are the uses and applications of plywood:
• If anywhere firm, strong material is needed then it is necessary.
• It is used as a high-quality layered wood material.
• Resistance to bend, split, break, crack, twist, warping made it important for construction and furniture making.
• For outdoor uses.
• For space shipping, aviation since 1939.
• Low moisture plywood used for different purposes like ship making.
• For making surfaces shaped curved, u, or folded plywood is used as the grains of plywood is easy to make bend than normal wood.
• To make the interior surface of skating ground this is used.
• Used for different interior games stadium.
• For ship construction.
• For space or aviation parts making

Plywood Manufacturing Process – Step by Step
Following are the main steps of plywood manufacturing process.
A. Selection of Log
B. Layer Formation
C. Exposure to Heat
D. Gluing
E. Baking
F. Finishing
A brief description of these steps is discussed below.
Selection of Log
The first step is the selection of a good log from selected tree wood according to the demand of the type of plywood to be manufactured. This log is known as peeler. Peeler is straight and has a good diameter as large number of layers are expected to make from it.
Layer Formation
The large blade is used for the processing of thin layers inside sawmill and made sheets of veneers. A horizontal placement of log under blade is maintained to get a better result. Continuously blade is pressed and several layers are cut into pieces.
Exposure to Heat
The sheets are then exposed to heat for removing water content from those. A good dehydration of sheets is confirmed before next step.
Gluing
After drying the sheets those are glued together maintaining the system of a different type of plywood. In this step, caution is maintained to get the best result. After patching and grading this gluing takes place. urea formaldehyde and phenol formaldehyde is used for gluing. And Furmecyclox is used for fungal resistance quality.
Baking
The glued plywood primary sheets are sent for baking and pressing at required temperature and pressure. The minimum temperature is 140 degree Celsius and pressure is 1.9 Mega Pascal.

Finishing
Finally, defects of manufactured plywood sheets are solved. Holes, pits or any unfinished edges are given finishing. Also resizing, reshaping takes place. Plywood is an engineered wood sheet material made up of fine layers or flimsy strands of wood veneers attached together placing wood grains 90 degrees to one another. It is one type of manufactured board which can be described as a mixture of Medium Density Fibreboard (MDF) and Chip Board (Particle Board).

Advantages of Plywood
Followings are the advantages of Plywood:
1. An alternation of the grains is done inside plywood which is called cross graining. It bears importance for some reason which increases the facility of plywood. Such as
o Cross grainging in plywood helps to avoid the possibility to split while the edges are nailed.
o It increases the strength of the material.
o It helps to bind the grains more tightly.
o Unnecessary expansion and wood shrinkage are avoidable for cross graining.
o Gives enriched spatial stability.
o Board consistency remains firm to all direction due to this.
2. Plywood has a reduced possibility to bend because odd numbers of plies are attached maintaining balance inside plywood.
3. The stiffness of plywood has made it hard to bend and inflexible.
4. Plywood helps to contribute to the economy.
5. While solid wood is heavy, furniture made from plywood are comparatively lighter to transfer.
6. Plywood has an ecological importance.

Disadvantages & Limitation of Plywood
Followings are the disadvantages of Plywood:
1. Urea and phenol formaldehyde used for gluing causes cancer.
2. Plywood is in many aspects weaker than wood.
3. Not durable like wood.
4. Not always easy to sculpture on this.
5. Lighter than normal wood.
6. Without some special resistance method maximum after long-term get attacked by insects.
7. Plywood cannot be exposed to wet or moisture weather for a long period of time.
8. The surface of plywood if not painted well can be peeled off.

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