DETERMINING OF THE ADHESION PERFORMANCES OF SOME WOOD GLUES IN MASIVES AND PANELS

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1 DETERMINING OF THE ADHESION PERFORMANCES OF SOME WOOD GLUES IN MASIVES AND PANELS Mustafa ALTUNOK, Tuğçe DEMİREZEN, Murat YILMAZ Gazi University, Technology Faculty, Wood Products Industrial Engineering Department, Ankara, Turkey. Key words Polyviniyl acetate, kleiberit 569, desmodur-vtka, Oriental beech, Scotch pine, chipboard, covered chipboard, MDF, adhesive strength, axional tensile test. Abstract In this study, adhesion performances of the glues which are used commonly in wood industry as polyvinylacetat (PVA c ), Kleiberit 569 (K 569 ) ve Desmodur-VTKA on woods such as Scotch pine (Pinus sylvestris Lipsky) and Oriental beech (Fagus orientalis Lipsky, on wood panel such as chipboard (Cb), coated chipboard (Cb c ), and medium density fiberboard (MDF) have been researched. For this purpose, with applying pure tension test to prepared test subjects according to the basis of TS EN 205, ASTM D 1037 and ISO 6237, subject matter of the survey which is adhesion strengths on the wood and wood-based material has been determined. According to the test results, in terms of materials, the highest adhesion strength is obtained from beech of the wood subjects, MDF of the panels, Kleiberit 569 of the glues, in the terms of interaction between material and glue beech glued with PVAc and Kleiberit-569 and MDF glued with Kleiberit 569. Corresponding author: altinok@gazi.edu.tr, Mustafa Altunok, Gazi University, Technology Faculty, Wood Products Industrial Engineering Department, Ankara, Turkey. 1. INTRODUCTION Furniture is a whole system composed of multiple elements. Especially, glue ensures that joints of wood furniture stay stable. With these strains, depending on the intensity of the force, it occurs deformations like loosening on joints of the furniture parts, bending on elements, cracking or breakings (Altınok, 1995). Because of glue, joints of furniture become rigid. Besides, with helping to make multiple panels, it contributes variety in furniture, economically and flexibility in design (Kurtoğlu, at al.,1993). That s why wood adhesives are very important in furniture industry (Bircan, 2000). The adhesives are the items that bonds the material to another with the features of superficial holding (adhesion) and internal resistance (cohesion) and don t change structure of the glued material so importantly ( Having been bonded with Desmodur-VTKA glue, Yellow pine wood (Pinus sylvestris L.) impregnated according to Tanalit CBC filled cell method was subjected to tensile strength test. A decrease in the adhesive strength of the glues in the impregnated samples has been reported (Özen, at al.,1997). The samples from Oriental beech, Yellowpine and Sessile oak woods prepared by using Desmodur-VTKA glue were subjected to tensile strength and shearing resistance tests after the processes of climatization, holding in cold and hot water, boiling and alternating boiling.

2 Results showed that they can be used in dry or damp internal and external settings (Özçifçi at al., 1997, Goetze at al.1987, Ors at al. 1998). Plain, rabbeted and 45 angled edge joints have been done on 19 mm thick particleboards by using UF (Urea formaldehyde) and PVAc (polyvinylacetate) glues. The tensile strength values measured at the bonding points were the highest for the one done with UV glue and rabbeted butt joint (16,1 N/mm2), average for the 45 angled edge joint (12,2 N/mm2), and the lowest for the butt joints(10,6 N/mm2) (Poblete-Wilson, 1988). Page 378 The highest tensile strength in the woods from Oriental beech, yellow pine, and sessile oak which were glued with Klebit 303, kleiberit 305 and super-lackleim 308 was obtained in Oriental beech glued with klebit 303 as (8,9 N/mm 2 ) (Ors at al.1999). In this study, adhesive strengths in the different reference surfaces (radial, tangential and transversal surfaces) of Oriental beech (Fagus orientalis Lipsky), sessile oak (Quercus petraea spp.), Yellow pine (Pinus sylvestris L.) and Taurus cedar (Cedrus libani A.Rich) bonded with commonly used glues in the industry K 303 ve K 305 and with no other auxiliary elements have been compared. K 303; can be used hot or cold in woodwork, wooden screens, multi-layered solid wood, slip joints. The producing company informs us that its density is 1,22 0,01 g/cm 3, its ph is around 7, viscosity mpa s at 20 C and it hardens under % 65 relative moisture and 20 C temperature conditions in 20 minutes (Ors at al.1999). In this study, it is aimed to determine the performances of adhesion of PVAc, Kleiberit 569 and Desmodur-VTKA glues on scotch pine and oriental beech, chipboard, melamine coated chipboard and MDF in accordance with basis of TS EN 205, ASTM D 1037 and ISO Adhesion Theory Adhesion occurs with adhesion bond which is the mutual gravity force of molecules and atoms of two different objects on their surfaces completely conflicted to each other Wood Adhesive line Wood Cohesion bond Adhesion bond Cohesion bond Figure 1. Adhesion and cohesion bonds in adhesion theory (Altınok,1998).

3 2. MATERIALS AND METHOD Wooden Material Experiment materials, which commonly used in woodworking Industry, Oriental beech (Fagus orientalis Lipsky), Scotch pine (Pinus silvestris L.), chipboard, covered chipboard and Medium Density of Fiberboard have been randomly selected and obtained from timber businesses Siteler Ankara in accordance with the principles specified in TS Page 379 Technical properties of glues The adhesives used in the experiment which emerged in the market in recent years and used mostly in assemblies and which do not contain solvents. Kleiberit 569 (K 569 ):Basis; Polyurethane, specific gravity at 20 C; approx. 1,05 g/cm³, colour; transparent opaque, consistency; pasty, thyrotrophic, application Temperature; from +5 C, application; beads, dots or spread over the surface, open time; approx. Polyvinyl acetate (PVA c ):Viscosity cp (20 0 C), ph ı 5 (20 0 C),specific gravity at 20 C; approx g/cm 3, press time; approx. 1 hour at 20 C with pressure of approx. 0.6 N/mm²,application; beads, dots or spread over the surface. Desmodur VTKA (Polimarin): It is named as Polimarin in the market. It is glue which is resistant to moist areas, lack of solvent, unifactorial and essential polyurethane (anonymous). Preparation of Experimental Samples The wood samples prepared in the dimensions of 10x20x150 mm, board samples of 18x50x50 mm and they were kept in acclimatization chamber under relative moisture conditions of 65 3 and a temperature of 20 2 C until a balance of moisture was achieved. Thus, initial differences of moisture were eliminated and average moisture of %12 was maintained. After the surfaces were glued, bonding was realized with a cold pressing pressure of 0,2 N/mm 2 and a pressing period of 60 minutes. Examples of wood and board are shown in Figure 2. Figure 2. Experimental samples of wood and board

4 Tensile test Samples of wood and board experiments of tensile strength were performed in compliance with the principles of specified in TS EN 205, ASTM D 1037 and ISO 6237 in a 4000 kp Universal test machine with a loading speed of 2 mm/min which was a steadily increasing static loading. Loading was applied until test samples were separated from adherence surfaces F max F max or broke and tensile strengths were measured from the equation N/mm 2 A ( axb) with the help of the maximum force (Fmax) measured during loading and adherence surface areas. Here; a = width of adherence surface (mm), b = length of adherence surface (mm) Page 380 Assessment of Data Separate multiple variance analyses were performed between the groups in order to determine the difference between adhesion strengths on joint (bonding) surfaces of test samples. The least significant difference LSD between the groups was determined with the Duncan test in order to see if the difference was significant. 3. FINDINGS It has been given the averages of adhesion strength calculated with the help of tensile forces belonged to every one of the samples glued with every one of the glues which are gathered in the tests at Table 1. Tablo 1. Average of adhesion strength on the materials and adhesives Adhesives and Adhesion strength (N/mm 2 ) Material types PVAc Kleiberit-569 D-VTKA Beech 14,32 14,33 11,88 Pine 12,34 12,38 12,47 Chipboard (Cb) 2,06 1,94 2,52 Covered Chipboard (Cbc) 0,26 3,47 2,91 MDF 3,16 3,56 3,15 According to results showed at Table 1; the highest adhesion strenght in terms of material has been obtained from beech of the wood samples, MDF of the panels. The diagram about this result has been given in Figure 3.

5 Adhesion strength (N/mm2) Adhesion strength (N/mm2) Adhesion strength (N/mm2) Proceedings of the 27 th International Conference 15 13,6 12, ,9 2,2 2,4 0 Beech Pine Cb Cbc Mdf Materials Figure 3. Graphic of adhesion strength on the wood and board materials Page 381 In terms of glue types, the highest adhesion strength has been found in glue of Kleiberit 569. PVAc and Desmodur-VTKA have almost the same results. The diagram about this result has been given in Figure 4. 7,4 7,2 7 6,8 6,6 6,4 6,2 6 Adhesive types 7,18 6,59 6,43 PVAc K-569 D-VTKA Figure 4.Graphic of adhesion strength on the Adhesive types According to the results of dual interaction between material and glue type, the highest adhesion strength has been found in beech of the wood samples glued with PVAc and Kleiberit-569 glues, MDF of the panels glued with the glue of Kleiberit 569. The weakest adhesion strength has been seen in coated chipboard glued with PVAc glue. The diagram about this result has been given in Figure PVAc K- 569 D-VTKA Beech Pine Cb Cbc MDF Material and adhesive types Figure 5. Graphic of adhesion strength on the adhesives and materials type

6 4. RESULT, DISCUSSION AND SUGGESTIONS According to type of material; the highest adhesion strength has been found on beech wood (13,6 N/mm 2 ), then on scotch pine (12,4 N/mm 2 ), and the lowest on flake board(2,176 N/mm 2 ) and coated chipboard (2,217 N/mm 2 ). The reason higher adhesion strength oriental beech has than scotch pine might have been resulted from oriental beech has more density and it doesn t involve resin in its wood form like pine. And the same result that has been seen in MDF of the panels might have been resulted from it s got a very straight surface and high internal adhesion strength. Number of 6 and 9 sources support this idea. Page 382 According to glue type the highest adhesion strength has been found in Kleiberit 569 (7,18 N/mm 2 ) and Desmodur-VTKA(6,59 N/mm 2 ), the lowest adhesion strength has been found in the glue of Polyvinylacetat (6,43 N/mm 2 ). It may resulted from Kleiberit-569 and Desmodur- VTKA have more cohesion force in their glue solutions. According to dual interaction between wood material and glue the highest adhesion strength have been found in samples of Kleiberit 569+oriental beech (14,34 N/mm 2 ) and samples of Polyvinylacetat + oriental beech (14,32 N/mm 2 ); the lowest adhesion strength have been found in samples of Polyvinylacetat + coated chipboard (0,2640 N/mm 2 ). It might has been gotten a high adhesion strength because of the cohesion force of Kleiberit-569 and high density of oriental beech. The highest adhesion strength in unnatural panels has been found in the samples of MDF glued by Kleiberit-569 glue (3,56 N/mm 2 ). It may has been resulted from MDF has higher adhesion strength than the others, its surface is very straight and because of low viscosity, Kleiberit-569 glue cannot go into inner surfaces of the panel. In oriental beech, adhesion strength of PVAc glue is higher than Desmodur VTKA glue. In wet environments the result is on the contrary. In literature, it has been stated Desmodur- VTKA glue can be used in dry or moist indoors or outer spaces. In this case, it can be said that Kleiberit 569 glue has high adhesion strength on the materials have been tested References Altınok, M. (1995), Sizing of durability elements according to stress analysis in chair design, doctoral thesis, Gazi University, Institute of Science and Technology, Ankara. Altınok, M. (1998), Effects of the Surface Bonding By Basic Woodworking machines Processed Wood Polytechnic Journal Volume 1, Issue 1-2, pp Bircan, M. C. (2000), Determination of Adhesion Performance Section Direction of some wood species with different glues without element, MS Thesis, Gazi University, Institute of Science.

7 Goetze, H., Schultze-Devitz, G. (1987), The Influence of Fillers and other Additional Subtances on the Bonding Strength of Adhesives with Solid Wood/Particleboard Joints, Drevorsky-Vyskum, n 114, p 41-46, 7 ref, Slowakian-Russion. Kurtoğlu, A., Kahvecı, M., Dilik, T., (1993), The Joining Shapes Used in the Production of Wood Furniture and Building Materials, publication no: B-40-3, p: 39-57, ISSN: , İstanbul. Ors, Y., Atar, M., Özçifç, A. (1998), Different Types of Wood with Chip and Fiber Sheets PVA or Desmodur VTKA Glue applied using dowel in the Tensile Strength, Turkish Journal of Agriculture and Forestry (In Press), Ankara-Turkey. Ors, Y., Atar, M., Özçifç, A. (1999), Bonding strength of the Klebit 303, 308 Lackleim KLEIBERIT and super-glue, Journal of Agriculture and Forestry, v. 23, n.3, Ankara, Turkey. Özen, R., Sönmez, A., Altınok, M. (1997), The Effect of Impregnation Wood Tanalit-CBC to the Bond strength, Communıgue XI. World Forestry Congress, p 55, Antalya-Turkey. Özçifçi, A., at al. (1997), Determine of Strength Joint of Polimarin Adhesive in Boiling, Cold and Hot Water Conditions of Wooden Materials, Proceeding of the XI. World Forestery Congress, Poblete-Wilson, H. (1988), Instituto de Tecnologia de Productos Forestales Ciencia-e- Investigacion-Forestal, Univesidat Austural de Chile, n 3, p 81-89, 6 ref, Valdivia- Chile. TS 2470 (1976), Wood Sampling for Physical and Mechanical Tests Medot and general features, TSE, Ankara. Page 383 Corresponding author: Mustafa Altunok, Gazi University, Technology Faculty, Wood Products Industrial Engineering Department, Ankara, Turkey. altinok@gazi.edu.tr, Author(s) This article is published under Creative Commons Attribution (CC BY) license.