(13)合板に關する研究(其之一)

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We will describe on the microscopical research about cracks of plywood and penetrate conditions of glue substances. I Materials Species of tree of three-plywood used in this research were as follows. [table] These plywoods were made of 1.3mm thick veneers. Glue substances were mixed with"Rakuto No. 2"100 parts, milk-casein 10 parts, caustic soda 1 part and water 275 parts by weight, and were spread over the surface of core about 50 gr per 1 ft^2. Pressure was 10〜20kg per 1 cm^2. Plywood was 4.0mm thick and it's size was 3×3ft. II Manufactures of Preparations and Photomicrographs. Size of wood piece was 1 cm in width and 2 cm in length. We got good results in defending the separaration of glue part merely by immerging wood pieces into the water at about 10℃. Immerging time of A plywood piece was from 30 minutes to 1 hour, B was 10〜30 minutes, C was about 2 hours, D was about 1 hour and E was abont 3 hours. Immerging time of wood piece, which has cross section of the face sheet and the back on longitudinal surface of the wood piece, can be cut short a little. Settling of wood piece must be practised in parallel with glue line in order to decrease separation. Good sections were made in case that the reverse side of two sheets among face, core and back sheet had faced to cutting direction. Sections were cu by Miehe's microtome, and the moderate direction angle of sword was 22〜33° and required it's enlarging in the order of A<E<B<C<D. Enlarging the direction angle of sword is required according to increase in specific gravity of plywood. Sections were 15μ thick, coloured in safranine, dehydrated in alcohol, treated in Oylol, and enclosed in Canada balsam. On all above treatments, carefulness was required in order to defend separation. Then, we made the microscopical study of preparations, and examined the photomicrographs of preparations. III Results and Considerations. 1 On cracks. The number and the length of plywood cracks, contained in glue line, per 1 cm in length on the cross surface at right angle to wood fiber of face, core and back sheet were as follows. [table] In this table, the cracks reaching over 1/2 of the sheet thickness from glue line are Large, 1/2〜1/4 are Middle, and within 1/4 are Small. Grain is the angle of annual ring with glue line. a. Cracks invade, in common, from reverse side of wood. b. Number of cracks is most great in ring-porous wood consisted of large vessels (Kalopanax r. and Quercus c.), and is next in diffuse-porous wood consisted of mepium vessels (Beturo r.), aud is smallin Diffuse-porus wood consisted of swall vessels (Tilia j. and Fagus c.). c. In case of the large angle of annual ring with glue line, cracks are many in number and laoge in length. d. Cracks in diffuse-porous wood consisted of small vessels are often straight along by ray. e. Cracks in diffuse-porous wood consisted of mediu msize vessels are narrower than those consisted of small vessels and many cracks connect vessel and vessel. f. Cracks in ring-porous wood consisted of large vessels often begin from vessel and end to vessel. g. We could not get numeral results about the width of cracks, but cracks of Fagus c. are the widest (there was a crack 100μ wide) and become swaller in the order of Tilia j., Quercus c., Kalopanax r., and Betula n. 2. On penetrate conditions of glue substances. a. Penetrate conditions in cracks. The longest glue penetrate length in the cracks adjacent to the glue line is 345μ, the largest distance from glue line is 234μ and the smallest in width is 9μ. b. Penetrate conditions in vessels. The smallest diameter of glue penetrate vessels connecting not with cracks is 40μ and the distance from this vessel to glue line is 50μ. The largest distance from the glue line to the glue penetrate vessel is 250μ, and the diameter of this vessel is 205μ. c. Penetrate conditions in case of cracks connecting with vessels. The longest penetrate length is 692μ and the largest distance from glue
日本森林学会の論文
1949-02-28

(13)合板に關する研究(其之一)

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