BOARDS

 BOARDS

Boards are the sheet like material made of various materials used as building materials and they are of varying thickness. Boards are used for the manufacture of furniture, as insulation boards and for other various purposes. Boards are of various types which are described below:

1) PLYWOOD (BASED ON MARKET SURVEY)

OBJECTIVES

The objectives of the field visit are listed as follows:

i.                 To know manufacturing processes of construction material i.e. ply wood.

ii.                To know their importance in buildings and their design.

iii.              To know the process those are implemented for the maintaining the properties of the material.

iv.              To know the condition of the industries and the condition of the manpower and machinery those are being used in the industries.

v.               To know the uses and rate of ply wood in the market of Nepal since ply is one of the important building materials nowadays.

PROCEDURE:

We our self visited the industries sites and collect the information with the managing board representative and labors that are working at the industries. We direct observed the different process of manufacturing ply wood. We have interviewed some workers and local people where an industry lies. Following are the industries that we observed:

i.                 Bira Furniture

Patan Industrial Area – Patan, Lalitpur

INTRODUCTION TO PLY

Ply is the wood based product manufactured from different layer of wood. This is made by cementing together several layers of wood which may be thin veneers or thicker boards where Veneers are thin sheets or slices of wood of superior quality, having thickness varying from 0.4mm to 0.6mm or more.

Following are the different machineries that are being used in this industry:

1.               SPeeling machine

2.               Chopping machine

3.               Sawing machine

4.               Dryer machine

5.               Glue splitter machine

6.               Pressing machine

7.               Sanding machine

8.               Finishing machine

9.               Sticker roller machine

The raw material i.e. wood of different types such as Utise, Sisal, Chilaune, Sal, etc. are taken up to here from different forest of Sindhuplanchowk, Gorkha, Dolkha, etc. districts. Different raw materials are also bringing from different sources especially in this industry.

According to workers of this industry seasoning is most important process to make plywood. Seasoning is the process of drying timber or removing moisture or sap present in a  freshly felled timber, under more or less controlled condition. If timber is used without seasoning, it is liable to shrink, warp, cracked and may even decay. This ply industry used both natural and artificial seasoning.

In natural seasoning, the industry used Air drying or seasoning. In this process the veneer is arranged one upon another, leaving space of few cms between them for the circulation of air. It takes around 2 – 3 hours in sunny day and may take about 2 – 3 days in winter season.

In artificial methods they used kiln seasoning process. This is quick and moisture contain in the veneer can control, by maintaining the temperature of around 145⁰C. The venner is passed into the hot chamber continually, after some minute the venner comes out from other side. This whole system is in under control. The heat that is required for this drying process is obtained from firing of waste wood and timber.

PLYWOOD PRODUCTION

Plywood production requires a good log, called a peeler, generally straighter and larger in diameter than the required for processing by a saw mill. The log is peeled into sheets of veneer which are then cut to desired dimensions, dried, glued together to form the plywood panel. The panel can then be patched, resized, sanded or otherwise refinished, depending on the market it was intended to be sold to. 

RATE IN MARKET

The plies that are manufactured in this industry are specially sold in Kathmandu and Sindhuplanchowk district. The local price of the 4mm ply is Rs.17 per square feet. The price may be changed according to place due to transportation cost. The price will increase according to the thickness of the ply and their quality. The plywood is then graded and packaged for shipping. Although plywood sheet thickness varies, standard thickness begins at 0.64 cm (0.25 in). The standard width and length of plywood are 1.22 by 2.44 m (4 by 8 ft).

OBSERVATION OR FINDINGS:

The different types of outcome of industries are reused inside the industry for the different process. Around 300 peoples work inside the industry and they are paid according to the scheme of the Nepal Government. Every labor has the insurance of minimum 1 lakh. The industry use fire work and heat system also. We found the well water pipe system in case of accident. The industry in is somehow away from residential area but it will better if it is transferred some safe place after some time. The surrounding environment is being slowly deteriorating.

Sources: -Plywood is made by gluing together a number of thin veneers or plies of softwood or hardwood.

Advantages: -There is always an odd number of veneers and each ply is at a right angle to the one below, this gives the material it's strength. The more veneers used, the stronger the plywood becomes. Both the type of glue and veneers determine the suitability of a sheet for a particular application. The finish quality of plywood varies considerably, some plywood have attractive grains while others can contain knots. Plywood may be used inside and outside. Plywood is graded for exterior or interior use depending upon the water resistance of the glue used to stick the plies together. Code letters shows this grading on each sheet.

Exterior grade plywood (WBP - Weather and Boil Proof). This type of plywood can be used outside. Water-resistant adhesives are used and can resist a certain amount of moisture.

Uses: -Sheds and cladding are made from this material.

Weather boiled proof plywood requires paint or varnish to protect the outer veneer from the elements.

Internal plywood does not contain water-resistant adhesive. The code used to represent this plywood is (In interior use only).

Uses: -It may be used for wall paneling, flooring and furniture.

Uses: -Shuttering boxes are made from shuttering plywood. Shuttering boxes are used in the construction industry to contain concrete while it sets. The material is water resistant to a certain extent. The surface of this material does not have a decorative veneer and is generally not suitable for use where an attractive quality finish is required.

Uses: -Marine Plywood is made with waterproof adhesive so that it can be used under water. The material should still be protected with paint or varnish.

Other codes used on the surface of plywood are: BR: -Boil Resistant, MR: -Moisture Resistant.

The smoothness of the surface and the number of defects in it grade plywood. Plywood can be nailed and screwed. Thin plywood is flexible and can be formed into curved shapes.

Sizes: -Plywood is sold in 2440 x 1220mm and 1525 x 1525mm sheets. The most common thicknesses are 4, 6, 9 and 12 mm. 

Plywood is used widely as a construction material because it is light, strong, durable, and inexpensive (the cost of producing plywood is often reduced by using less-costly wood for the inner layers). Plywood resists warping and cracking, and is moderately flexible because the grain direction of each layer is alternated.

Plywood is used to underlay floors, roofs, and walls in homes and buildings. It is used for making boats, truck campers, trailers, highway signs, pallets, bins, and other crating. Plywood is used to make concrete forms for basements, bridges, and other foundations. Plywood is also used for decorative applications inside the home, including furniture, cabinets, and interior wall panels.

While softwood plywood is typically used by the construction, transportation, and container industries, hardwood plywood is more commonly used for decorative applications. Most softwood plywood is made from Douglas fir and southern pine, while hardwood plywood is made from birch, oak, cottonwood, mahogany, and other tree species.

2) GYPSUM BOARD

Gypsum board, also known as plaster board or dry wall, is a panel made of gypsum plaster pressed between two thick sheets of paper. It is used to make interior walls and ceilings. Plasterboard panels are also known as wall board.

The sheets of the drywall can be made from fiberglass instead of paper to prevent mold growth. Mold growth is common when using paper-based plasterboard that has been exposed to water due to plumbing leaks or floods.

Drywall construction became prevalent as a speedier alternative to using plaster based interior finish techniques, which involved forcefully spreading a substrate of coarse plaster, known as the base (made up of the scratch coat and (optional) brown coat), onto the wall's lath-work before finally applying the smoother finish coat, each layer added in succession and all by hand. Drywall, by contrast to plaster, requires hand finishing only at the fasteners and joints. The drywall process requires less labor and drying time, lending its name to the panels used in the assembly.

Manufacture

A wallboard panel is made of a paper liner wrapped around an inner core made primarily from gypsum. The raw gypsum, CaSO₄·2 H₂O, (mined or obtained from flue gas desulfurization (FGD) must be calcined before use to produce the hemihydrate of calcium sulfate (CaSO₄·½ H₂O). This is done in kettle or flash calciners, typically using natural gas today. The plaster is mixed with fiber (typically paper and/or fiberglass), plasticizer, foaming agent, finely ground gypsum crystal as an accelerator, EDTA, starch or other chelate as a retarder, various additives that may increase mildew and/or fire resistance (fiberglass or vermiculite), wax emulsion or silanes for lower water absorption and water. This is then formed by sandwiching a core of wet gypsum between two sheets of heavy paper or fiberglass mats. When the core sets and is dried in a large drying chamber, the sandwich becomes rigid and strong enough for use as a building material.

Drying chambers typically use natural gas today. To dry 1 MSF (1,000 square feet) of wallboard, between 1.75 and 2.49 million BTU is required. Organic dispersants/plasticisers are used mainly to reduce the amount of water, hence reduce the eventual drying time, needed to produce gypsum slurry flow during wallboard manufacture.

3) FIBRE BOARD

Fiberboard is a type of engineered wood product that is made out of wood fibers. Types of fiberboard (in order of increasing density) include particle board, medium-density fiberboard, and hardboard. Fiberboard is sometimes used as a synonym for particle board, but particle board usually refers to low-density fiberboard. Plywood is not a type of fiberboard, as it is made of thin sheets of wood, not wood fibers or particles. Fiberboard, particularly medium-density fiberboard (MDF), is heavily used in the furniture industry. For pieces that will be visible, a veneer of wood is often glued onto fiberboard to give it the appearance of conventional wood.

Fiberboard is also used in the auto industry to create free-form shapes such as dashboards, rear parcel shelves, and inner door shells. These pieces are usually covered with a skin, foil, or fabric such as cloth, suede, leather, or polyvinyl chloride.

Urea-formaldehyde (UF) resins are dominantly used in the medium density fiberboard (MDF) industry because of their low cost and fast curing characteristics. However, pressures on the use of UF resins are mounting steadily due to potential problems associated with formaldehyde emission. On the other hand, phenol-formaldehyde (PF) resins are more durable and do not emit formaldehyde after cure. But the Industry has traditionally shied away from using PF resins due primarily to their higher cost and much slower curing rate than UF resins. However, the press times PF-bonded fiberboard can be substantially reduced by manipulating the fiber mat temperatures, molecular weight distribution of PE resins and pressing parameters. As a result, the press times for PF-bonded fiberboard can be made comparable to those for UF-bonded fiberboard. Also, the resin content required for PF-bonded fiberboard is less than 5% to achieve a good board quickly. This is considerably lower than that required for UF-bonded fiberboard.

Certain types of fiberboard can be considered "green" building products. Consisting of bio-based, secondary raw materials (wood chip or sugarcane fibers) recovered from within 100 miles (160 km) of manufacturing facilities, the binding agent used in this type of fiberboard is an all-natural product, consisting of vegetable starch containing no added formaldehydes.

 Different uses and applications:

• sound proofing/deadening,
• structural sheathing,
• low-slope roofing,
• sound deadening flooring underlayment

4) PAPER BOARD

Paperboard is a thick paper based material. While there is no rigid differentiation between paper and paperboard, paperboard is generally thicker (usually over 0.25 mm/0.010 in or 10 points) than paper. According to ISO standards, paperboard is a paper with a basis weight (grammage) above 224 g/m², but there are exceptions. Paperboard can be single or multi-ply. Paperboard can be easily cut and formed, is lightweight, and because it's strong, it's used in packaging. Another end-use would be graphic printing, such as book and magazine covers or postcards. Sometimes it is referred to as cardboard, which is a generic, lay term used to refer to any heavy paper pulp based board.

Different types of Paper board:

·       Boxbord or cartonboard – paperboard for folding cartons and rigid set-up boxes

·        Folding boxboard (FBB) – a bending grade capable of being scored and bending without fractu

·        Chipboard – all recycled, low quality board

·        Kraft board – a strong virgin fiber board often used for beverage carriers. Often clay coated for printing

·        Laminated board – a lamination of paperboards and other materials, for example Liquid packaging board

·        Solid Bleached Board (SBB) or Solid Bleached Sulphate {SBS) – clean white board used for foods etc

·        Solid unbleached board (SUB) – board made from unbleached chemical pulp

·        White lined chipboard (WLC) – a white, often clay coated, chipboard

·        Containerboard – a type of paperboard manufactured for the production of corrugated fiberboard

• Corrugated medium – the inner fluted portion of corrugated fiberboard
• Linerboard – a strong stiff board for one or both sides oh the medium
• Other
• Binder's board – a paperboard used in bookbinding for making hardcovers.

Production

Fibrous material is turned into pulp and bleached, to create one or more layers of board, which can be optionally coated for a better surface and/or improved visual appearance. Paperboard are produced on paper machines that can handle higher grammages and several plies.

Raw Materials

The above mentioned fibrous material can either come from fresh (virgin) sources (e.g. wood) or from recycled waste paper. Around 90% of virgin paper is made from wood pulp. Today paperboard packaging in general, and especially products from certified sustainable sources, are receiving new attention, as manufacturers dealing with environmental, health, and regulatory issues look to renewable resources to meet increasing demand. It is now mandatory in many countries for paper-based packaging to be manufactured wholly or partially from recycled material.

Raw materials include:

• Hardwood: Ca .05 inches (1.3 mm) (length) e.g. Birch which has short fibres. It is generally more difficult to work with; however, it does provide higher tensile strength, but lower tear and other strength properties. Although its fibres are not as long and strong as those in softwood, they make for a stiffer product defined by some stifness tests. Hardwood fibres fill the sheet better and therefore make a smoother paper that is more opaque and better for printing. Hardwood makes an excellent corrugating medium.

• Softwood: Ca .13 inches (3.3 mm) (length) e.g. Pine and spruce which have typically long fibres and make superior paperboard in services where strength is important. Softwood makes excellent linerboard.

• Recycled: Used paper is collected and sorted and usually mixed with virgin fibres in order to make new material. This is necessary as the recycled fibre often loses strength when reused; the added virgin fibres enhance strength. Mixed waste paper is not usually deinked (skipping the deinking stage) for paperboard manufacture and hence the pulp may contain traces of inks, adhesives, and other residues which together give it a grey colour. Products made of recycled board usually have a less predictable composition and poorer functional properties than virgin fibre-based boards.

Multi-ply paperboard generally has higher creasing and folding performance than single-ply as a result of layering different types of pulp into a single product. In cases where the same kind of pulp is being used in several layers, each separate layer is treated and shaped individually in order to create the highest possible quality. The benefits of multi ply paperboard are for example its higher creasing and folding performance.

5) Hard board

Hardboard, also called high-density fiberboard, not to be confused with 'hardwood', is a type of fiberboard, which is an engineered wood product.

It is similar to particle board and medium-density fiberboard, but is denser and much stronger and harder because it is made out of exploded wood fibers that have been highly compressed. Consequently, the density of hardboard is 31 lbs. or more per cubic foot (500 kg/m³)[1] and is usually about 50-65 lbs. per cubic foot (800-1040 kg/m³). It differs from particle board in that the bonding of the wood fibers requires no additional materials,[2] although resin is often added. Unlike particle board, it will not split or crack. It is used in construction and furniture. Hardboard is produced in either a wet or dry process. The wet process leaves only one smooth side and dry processed hardboard is smooth on both sides.

Uses

A product resembling hardboard was first made in England can be glued onto it to give the appearance of solid wood. Other overlays include formica, laminated papers and vinyl. It has many uses, such as a substrate. It is used in construction, flooring, furnit home appliances, automobiles and cabinetry, and is popular among acrylic and oil painters as a painting surface due to its economical price (though it must be coated with gesso or canvas before use). It is also used as the final layer in many skateboard ramps and the half-pipe.

Tempered hardboard is hardboard that has been coated with a thin film of linseed oil and then baked; this gives it more water resistance, impact resistance, hardness, rigidity and tensile strength. An earlier tempering process involved immersing the board in linseed oil or tung oil until it was 5 to 6 percent saturated, and heating to 170° C (340° F).[4] Tempered hardboard is used in construction siding.

Perforated hardboard, also called pegboard, is tempered hardboard that has rows and columns of 1/8" or 1/4" holes in it, into which hooks can be placed for hanging tools