Blockboard
is a kind of engineered compound plywood board where softwood strips are joined
sideways and machined together, often a sandwich structure, with hardwood
between them. Block board is usually found in various sizes and thicknesses.
The common size of a block board is 2440 x 1220 x 30 mm.
According to I.S Code: 1659, the thickness of the blockboard can be 12 mm, 15 mm, 19 mm, 25 mm, 30 mm, 35 mm, 40 mm, 45 mm or 50 mm.
Standard sizes of the block boards available in the market are given below:
|
in mm |
in feet |
|
2440 x 1220 |
8′ x 4′ |
|
2140 x 1220 |
7′ x 4′ |
|
2140 x 920 |
7′ x 3′ |
|
1830 x 1220 |
6′ x 4′ |
|
1830 x 920 |
6′ x 3′ |
The price of blockboard is always calculated per square foot. The price range of blockboards may vary depending on the type, size, and sheet thickness of the inner core wood species (softwood or hardwood).
Prices range from 90 to
150 rupees / sq.ft for commercial blockboard and 120 to 200 rupees / sq.ft for
water proof blockboard.
Types of Blockboard:
The classification of
block boards depends on various properties such as quality, usage, raw wood.
Following are the types of blockboards:
A. Depending on quality
and usage:
1. Interior grade
blockboard
2. Exterior grade
blockboard
B. Depending on the raw
wood used in the core:
1. Softwood Blockboard
2. Hardwood Blockboard
Various
aspects of these types are briefly discussed below:
Interior grade blockboard
These grades are
designed for indoor use which are resistant to moisture and are known as MR
(moisture resistant).Examples are: Furniture, door, window shutter.
Exterior grade blockboard
This variety of blockboard is manufactured for outdoor use. These are termed as BWP (Boiling Water Proof) or BWR (Boiling Water Resistant). They have high quality of resistance because the adhesives used here are also good in quality.
Softwood block board
Wooden solid blocks are
used to make each blockboard sheet that is joined together using glue. The
sheets are termed as strips or battens. The surface is covered with hardwood
veneer.
Hardwood block board
Hardwood is dense,
heavy, expensive, strong. The coating is also characterized by hardwood.
Technical
Properties of Blockboard:
Density
Bending strength
Cross bending strength
Formaldehyde emission
Modulus of elasticity (long)
Modulus of elasticity (cross)
Fire Protection Range
Thickness tolerance
Length and width
tolerance
Blockboard processing
The following are the
steps of blockboard processing:
1. Slicing
The logs of wood have
been pre-sliced to make the blocks raw. The strips can be 25 mm.
2. Rotary Cutting
For the outer layer,
the log is cut by rotary cutting. Thus veneer is obtained for coating.
3. Gluing
Slices are add with
glue or adhesives. For example: Urea formaldehyde, phenol formaldehyde called
plastic resin. The outer grade block board requires phenol formaldehyde. Gluing
is done under high pressure.
4. Drying
The blocks are dried to
reduce moisture and also the amount of water that is left inside the blocks.
Blocks are placed before the sun for drying. The moisture content decreases to
10–12%. After proper drying, they are ready to make a sandwich.
5. Attaching
The blocks are joined
together using either the softwood or hardwood required for internal or
external grades.
6. Finishing
A coating is done,
giving the final finishing lamination.
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