JOURNAL OF MATERIALS SCIENCE LETTERS 19,2000,1267—1269

Deterioration of wood wastes-based molding materials by using several fungi

M.  H. ALMA

Department of Industrial Engineering of Forestry, Kahrmanmaraş  Sütçü Imam University, 46060 K. Maras-Turkey

E-mail:  alma@ksu.edu.tr  

M.  DIĞRAK

Department of Biology, Kahramanmara~ Sutcu Imam University, 46060 K.Maras-Turkey E-mail: mdigrak@hotmail.com

I.    BEKTAŞ

Department of Industrial Engineering of Forestry, Kahrmanmara~ Sütçä Imam University, 46060 K.Maras-Turkey

The phenolated wood and molding materials from it were prepared by conventional methods. The pheno­lated wood and commercial novolak resin-based mate­rials were incubated by using soil and broth methods along with various fungi and then biodegradabilities of the materials weie evaluated by taking weight loss into consideration as a function of various fungi and material types. The results showed that phenolated wood-based molding materials had much more weight loss per cent when compared with commercial novolak resin-based ones. Furthermore, it could be said that the broth test resulted in a much greater weight loss than the soil test and, except for Aspergillus candidus, all the other fungi (e.g., Fusarium equiseti, Byssochlamys fulves, Sordaria, fimicola, Penicilliumfrequentans) used were found to be effective in achieving a large weight loss.

The use of lignocellulosic wastes as replacement for synthetic materials and the recycling of the munici­pal wastes, consisting largely of wood-based materi­als, have become important issues recently because of scarcity and cost of petroleum resources and decreas­ing landfills, particularly, in industrialized countries. Therefore, recycling is the most acceptable disposal method in the long run and useful both for ecology and economy. Also, the processing cost of lignocel­lulosic wastes is very low in comparison to synthetic wastes [1].

Moreover, an urgent necessity to develop biodegrad­able, photodegradable, chemidegradable and envi­rodegradable polymeric products has been increasing from the ecology point of view, requiring that biomass should be incorporated into biodegradable materials

[1,2].

As yet, we have successfully done a variety of stud­ies on making wood-based molding material by us­ing phenol as solvent and acidic catalysts (e.g., hy­drochloric acid, phosphoric acid, sulfuric acid etc.) [2, 3]. However, no attempt has been made to evaluate the biodegradabilities of these materials systematically. In this study, we aimed primarily at measuring the biodegradability of the materials by using several Se­lected fungi and conventional methods (e.g., soil and broth methods) and comparing the obtained results with that of novolak-based ones.

Birch (Betula maximowicziana Regel) wood meal (20-80 mesh) was used as biomass waste. “Guaran­teed reagent grade” phenol and sulfuric acid (cata­lyst) were used for phenolation. In addition, “Commer­cial grade” hexamethylenetetramine (HMTA) (curing agent) (which was donated by Mitsubishi Chemical Co. Ltd, Japan), zinc stearate (lubricating agent), calcium hydroxide (accelerating agent), and wood flour (filler) components (which were donated by Hitachi Chemical Co. Ltd, Japan) were used as molding components. All the other chemicals used in this study were provided by Aldrich Chemical Co. In addition, commercial no­volak resin (Novolak, 700 NK), which was supplied by Hitachi Chemical Co. Ltd., Japan, was used as a refer­ence commercial product.

In this study Fusarium equiseti, Aspergillus can­didus, Sordaria fimicola, and Pen icillum frequentans, and Byssochlamys fulves fungi were used. The fungi used in this study were provided from the collection of Biology Department of Science & Literature Faculty of Uludag University in Bursa]Turkey. The fungi were kept in Malt-Extract Agar (MEA) medium at 4 ⁰C.

A mixture of a vacuum oven-dried wood meal, phe­nol, and sulfuric acid was heated in a three-necked round bottom flask at 150⁰C for 1 h. The result­ing mixture thus obtained was diluted with methanol and filtrated with a glass-fiber filter (Toyo GA-100). The methanol-insoluble parts, the so-called “wood residues”, were oven-dried for 24 h and weighed. The soluble parts were first evaporated at 50⁰C under vac­uum and then concentrated at 1 80⁰C under a reduced pressure of about 45 mm Hg for 1 h by removing the free phenol. The solid product so obtained will be called phenolated wood.

Ten grams of the phenolated wood obtained as above and commercial novolak resin were blended with 2.5 g of HMTA as a hardener, 13.1 g of wood flour as a filler, 0.64 g of Ca(OH)₂ as an accelerator and 0.3 g of zinc stearate as a lubricating agent. Five grams of the result­ing molding compound was molded into a specimen with dimensions of 4 x 10 x 80 mm at 190⁰C under 39.2 MPa for 5 mm.

The fungi were incubated for 7—14 days having been injected into MEA medium at 25⁰C [4, 5]. Then, 10 mL

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