Wood Seasoning & Preservation Division

Introduction

       Research activities of this division are to find appropriate technologies for value addition to non-durable timbers from plantations and other secondary timbers. The detailed research activities of the division are as follows

Objectives

       In this division research in Wood Seasoning and Preservation has been directed to find appropriate technologies for value addition to non-durable timbers from plantations and other secondary timbers. These include techniques for over coming residual growth stresses in logs for obtaining maximum out-turn on conversion, finding appropriate seasoning techniques, improvement of dimensional stability, chemical modification of wood for specialised applications, studies on mechanism of weathering and its protection, development of wood polymer composites, development of suitable preservatives, their application techniques and above all to demonstrate the advantages to users.

Research Activities

Growth Stresses in Plantation Timber:

       High level of growth stresses inherent in fast growing plantation trees and their logs causes extensive warp/crook, non-uniformity in thickness during sawing and seasoning. A microprocessor based multi-channel instrument for measuring strain using "strain gauge" was designed and fabricated for assessment of strain in the timber logs by non-destructive methods. This helps in choosing appropriate sawing procedure to obtain optimum yield.

Modification in Solar timber seasoning kiln for increased energy efficiency:

       In view of the high investment cost of kiln, their operation and maintenance, very few saw millers are undertaking on commercial scale the job of processing wood for different end users. In the absence of kilns, which can be cost effective, large volume of wood is being utilised without proper processing. Solar timber seasoning kilns though appropriate to small requirement of furniture makers, handicraft industry etc., yet, are not being widely adopted in industry due to low energy efficiency. For rectification of these deficiencies studies were made and a single glass wall with blackened wire mesh for side walls has been recommended for significant gain in heat trap. Additional heat gain achieved in this design could be used for longer duration of operation of kiln after the sun set.

Wood Preservation:

       Data on durability of timbers from plantations and from natural forests under untreated as well as on treated with different preservatives have been tested and documented for use of wood users.

Although wood is versatile material for varieties of uses it is biodegradable and needs protection so as to enhance serviceability. Conventional method of treating wood material is by subjecting it to pressure treatment or by diffusion treatment which involve machinery and skilled labour. Since investment on these are expensive , many wood processing industries are reluctant to adopt the technology.

       A simple SAP DISPLACEMENT TECHNIQUE which does away with the elaborate plant and skilled man power and which can be carried out at felling sites obviating transportation of poles to a centralised pressure treatment plant has been standardised at this Institute. Species that can be treated with this technique are: Bamboo, Eucalyptus. Treatment enhance the life of material by 4-5 fold.

       Pre-weathering causes chemical and physical changes on wood surface due to photodegradation and weakens subsequently coated paint by developing crack/blister. This result in peeling of film coat and reduction of life span of coated paints. Also, refinishes are required for their protection which involve additional recurring cost. Treatment of substrate by ammonical copper chromate and chromic acid solution was observed to prevent above drawbacks effectively.

       Pterocarpus marsupium (bijasal), Shorea sp. (Red meranti) imported from Malaysia are used in house building construction for door, window frames and other joinery work. They possess considerable amount of water leachable extractives which reduces the quality of paint coatings when in contact with water. Simple brush coat of dilute aqueous solution of chromic acid before any finishing by paint or polish was found to be an effective reagent to check the process of leaching.

       Hevea brasiliensis (Rubber), Mangifera indica (Mango) and Acacia auriculaeformis are extensively used in furniture, door and window frames, black boards etc., They suffer from dimensional instability due to high shrinkage and swelling under varied atmospheric conditions. Chromic acid and acetic anhydride are found to impart good water repellency to wood even when used under short(repeated) cycles of wetting and drying.

Wood Polymer Composites:

       Specialised wood products such as textile accessories, parquet flooring, have stringent specifications such as dimensional stability hardness and toughness characteristics in wood. In view of shortage of such timber suitable for such end uses demand from industry for alternatives or substitutes is considerable. Maximum weight gain of 90% was achieved in wood of Hevea brasiliensis and Mangifera indica when impregnated with styrene and methyl metha acrylite (MMA) and polymerised in-situ by free radical polymerisation using a heat catalyst. Polymerised wood was found to possesses the desirable properties.

       Wood fibers of Eucalyptus were grafted with styrene using aqueous solution of Mn³⁺ ions at pH 6.0. to enhance compatibility between wood fibre and synthetic polymers by different coupling agents and grafting. Polymer loading as high as 200% and a maximum grafting efficiency of 90% was achieved. Composites from grafted wood fibers were prepared with polystyrene at 5,10,15 and 20% fiber loading, using a laboratory extruder. Wood fiber filled composites exhibited superior tensile strength and impact strength..

Services Rendered

Facilities and Equipments

       The division has the following facilities and expertise for rendering services to user industry and Government and non-government organisations:

• Xenotest weathero meter for accelerated weathering experiments.

• Timber seasoning kiln and expertise for setting up solar seasoning kiln.

• Pressure-treatment plant for preservative-treatment of timber.

• Workshop for processing wood samples for various experiments.

• Advice on simple, inexpensive wood-preservation techniques (sap displacement method).

• The division's laboratories are well equipped with (a) SpectroFLUORO meter.

Research Staff

1. Dr. Krishna Kumar Pandey, Scientist-F, Head of the Division

2. Mr. P. Narayanappa, Scientist-E

3. Mr. Ajay G. Karmarkar, Scientist-E

4. Mr. Pankaj Kumar Aggarwal, Scientist-E

5. Dr. Shakti Singh Chauhan, Scientist-D

6. Ms. D. Venmalar, Scientist-B

7. Ms. C.N. Vani, Research Assistant, Gr.-I

For further information, Please contact:

    The Head

    Wood Seasoning and Preservation Division

    Institute of Wood Science and Technology

    P.O. Malleswaram

    Bangalore-560 003 (India)

    E-Mail: wsp_iwst@icfre.org