PLYWOOD

FWT - KU

In 1797 Samuel Bentham applied for patents covering several machines to produce veneers.

About fifty years later Immanuel Nobel, father of Alfred Nobel, realized that several thinner layers of wood bonded together would be stronger than one single thick layer of wood.

plywood manufacture was an established process in France in the 1860s.

Plywood was introduced into the United States in 1865.

In 1928, the first standard-sized 4 ft by 8 ft (1.2 m by 2.4 m) was produced

History of Plywood

Panels comprising of at least three layers of thin wood bonded together with an adhesive.

Each ply is usually orientated at a right angle to the adjacent layer in order to improve strength and reduce the probability of shrinkage.

Plywood is a manufactured wood equally panel from thin sheet of wood veneer. It is one of the mostly used wood products.

Definition

“Face & back” are commonly preferred for outer Layer of ply and graded according to their quality. The inner or intermediate layer are collectively known as “core”.

Plywood is flexible, inexpensive, workable & re-usable and usually can be manufactured locally, resistance to cracking, splitting, shrinkage, twisting and has high strength.

Definition (Cont’d)

These are thin sheets or slices of wood of superior quality.

Dimension:Usually 0.5 to 1.0 mm in thickness. Sometimes up to about 10mm.

Veneer

All species may be used for production for production of veneer.

Softwood and hardwood species with a uniform texture without large differences between early wood and latewood are used.

Tropical woods are extensively used due to absent of pronounced growth rings.

Sources of Veneer

Should have straight and round log

Should be defect free on log surface

Should have a centered pith, uniform color and growth rate

Should be free from mineral deposit.

Criteria of Veneer Trees

Decorative Veneer: It is used for surface furniture, interior plywood paneling and related products.

Utility veneer: It is used for partitions of furniture and cabinets and other structural uses or in products coated with paint or other materials.

Veneer Types

1. Sizing of veneer logs

2. Storage of veneer logs

3. Debarking

4. Pretreatment

5. Veneer cutting

6. Veneer handling and green clipping

7. Veneer Drying

Preparation of Veneer

Preparation of Veneer (Cont’d)

Step 1: Preparation of veneer

Step 2: Veneer Drying

Step 3: Jointing and Splicing of dry veneer

Step 4: Mixing and spreading of adhesive

Step 5: Pressing of Plywood

Step 6: Conditioning & finishing

Manufacturing Process of Plywood

Manufacturing Process of Plywood (Cont’d)

Manufacturing Process Flow Chart

Urea formaldehyde(UF)

Phenol Formaldehyde(PF)

Melamine formaldehyde(MF)

Isocyanides

Plywood Sizes and Thickness

General dimensions are 8x4, 8x3, 7x4, 7x3, 6x4 and 6x3 sq. feet.

The general thickness ranges are 1/4", 3/8", 1/2", 5/8", 3/4", 1" and sometimes higher.

Adhesives Used and Plywood Dimensions

Commercial plywood

Waterproof plywood

Marine plywood

Softwood plywood

Hardwood plywood

Tropical plywood

Flexo plywood

Aircraft plywood

Decorative plywood

Types of Plywood

•It is an interior grade plywood for indoor Use

•It has light colour shades.

Commercial Plywood

• Waterproof ply is mostly used• It has black collared shades• Due to chemical used in it , it don’ t get affected

by termite• Black colour is also due to chemicals used.

Waterproof Plywood

• It is flexible and is used for making curved

parts

• All the grains go in one direction.

Flexo Plywood

• It is a form of plywood that has been constructed using waterproof veneer to make it suitable for use in wet environments including a home built boat , and other structures.

• It may serve as underlayment of boat, deck cover, the wall and compartment overhead panels of boat.

Marine Plywood

• Softwood panel is usually made either of cedar , pine , redwood , and is used for construction and industrial purpose

• The most common dimension is 1.2 m x 2.4 m or large imperial 4’ x 8’

• Thickness is from 1.4 mm – 4.3 mm.

Softwood Plywood

• It is made from angiosperms trees and is used for demanding end uses

• Especially suitable for heavy duty floor and wall structures

• It has excellent surface hardness , damage and wear resistance.

Hardwood Plywood

• Tropical plywood is made from species of tropical wood• Originally from the Asian region , it is now also

manufactured in African and south American countries• Tropical plywood is superior to softwood plywood due

to its strength , density and high quality• Tropical plywood is used widely in UK, Japan, US,

Taiwan, Dubai and other countries.

Tropical Plywood

• High strength plywood is also known as aircraft plywood

• It is made from birch and mahogany and uses adhesive with increased resistance to heat and humidity

• It was used for several world war 2 fighter aircraft• Although the british built mosquito bomber nicknamed

“the wooden wonder”, it was constructed using plywood having indiviual veneers of birch, balsa.

Aircraft Plywood

• Usually faced with hardwood including ash, oak, red oak, birch, maple, mahogany, rose wood, teak and large number of other woods

• This plywood is lot easier to dye and draw on than any other plywood.

Decorative Plywood

• BWR : boiling water resistant

• BWP : boiling water proof

This grade is mostly used in kitchens.

• MR : moisture resistant

Plywood Grades

Dimensional stability

Uniform strength in along & across the board

Resistance to warping , cracking & twisting

Economical & affective utilization of wood

Use of fast growing & non durable species

Solid wood is 20 times stronger along the grain

than across. Plywood over 10mm thick is almost

equal in strength in both directions

Plywood can be formed or bent to make a curve.

Advantages of Plywood

Veneer Checking

Discoloration of plywood

The layering effect in plywood makes it porous and susceptible to water damage if exposed over time. Plywood becomes heavy when wet

Because plywood is fibrous, it will easily absorb water and water vapor, causing it to bubble or delaminate.

Disadvantages of Plywood

Floors, walls and roofs in house constructions

Furniture Structure panel Vehicle internal body

work Packages and boxes Fencing Floor base Container flooring

Uses of Plywood

Playground equipment Musical instruments Sports equipment High-end loud speakers Fences for demanding

outdoor advertising

Uses of Plywood (Cont’d)

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