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HAMADA, Ryozo

MAKU, Takamaro

Kyoto University Research Information Repository

Title Studies on the chipboard : Part 2. Swelling properties ofchipboardAuthor(s)MAKU, Takamaro; HAMADA, RyozoCitation木材研究 : 京都大學木材研究所報告 (1955), 15: 53-59Issue Date1955-09URL http://hdl.handle.net/2433/52815RightType Departmental Bulletin PaperTextversionpublisherKyoto UniversityStudies 011 the chipboardPart 2. Swelling properties of chipboardby Takamaro MAKU and Ryozo HAMADAThis report is the results of investigations on the effects of manfacturingmethod 'on the swelling properties of chipboard.I Experemental methodThe size of chips used are· 20 "'" 30 mm long, 1.5 mm wide, and 0.2 mm or 1.0 mmthick. Preperation of panel is made in the same· way as in report I excepting that urea'resin added is diluted with water to the required density.Test pieces are 5 cm X 5 cm area and 4 "" 6 mm thick and they are immersed in wat~r! '. '~.for 20 hours after oven dried. Rate of water absorption and expansion in thickness\;iscalculated by following formulas.Rate of water Weight after immersion - Wi:;ight of oven dried 100absorption (%) = Weight of oven dried X~~~ o~ e:fick: = Thickness after immersion - Thickness of oven dried 100Thickness of oven dried' Xness (%)II. Experimental results and discussions1. Effect of binder on the swelling properties of chipboard. "First, experiments were done about the effect of curing conditions of urea and form-aldehyde on the sNelling properties of chipboard. Though the effect of catalyzer, valueof pH, heating temperature, heating time, and etc. on the swelling properties of panelwere not reina~kable, the good result was obtained. when the curing was proceeded incomparatively high temperature under the adjustment of pH between 7.5 to 5.4 with.NH40H and NazHP04 as catalyzer as shown in Table 1.The relation between lllol ratio of urea to formaldehyde awl the thickness recoveryof chipboard is' shown in Fig. 1 and according to this figure it seems that the stabilityof panel is increased at the small value of ratio and this value deviates slightly from- {)3 -WOOD RESEARCH NO. 15 (1955)Figi. Effect of mol ratio of urea ( U) and formaldehyde (F)on the rate of expansion in thickness.U:F""J:lltJ : 7.77: 2.07:253 5 6 7 8,.Resin content9 70 %Table 1. Curing condition of urea fromaldehyde resin\. Water l' heatin g \h.eating. temp. timepHI, lZ 7.5';"'5.41st Process 125 310 1 0 0 gooC 30'2nd // 25 0 3,5 0 0 6.8~6. 0 25 93°C 30'3nd '// 0 I 0 0 0 1.57.0 0 55°C 30'I ,reasonable one in preperation of urea resin adhesive. From this results the authers pre-sume that, in case of chipboard, amount of adhesive added is so little that adhesive musthave strong affinity to wood.The effect of viscosity or density of binder on the swelling properties of chipboardare presented in Fig. 2 '" 3.Fig. 2. Effect of density and viscosity of resin on water absorptIon andthickness recovery of panel. (thickness of chip: 0.2 mm)3230;:::28.t::l~ 26~2/,lC\l'ls 22~' 20~78767f/-RelativeDensity ViSCOSity6. •••- 50 % 40.6)( '--' 35 5.2• ----, 20 2.2%1';:90~~80 S<.1670 $l60~5 678Resin content9 70 . 77 %T. MAKU and R. HAMADA: Studieson the chipboardWhen the panel was made of thin chips, swelling properties of board were unaffectedby the density or vis:osity of urea resin (Fig. 2). On the contrary in case of thickchips, thickness recovery and water absorption of panel Increased by increasing -of densityor viscosity of resin (Fig. 3). For the reason of this phenomenon, the authors supposethat in case of low viscosity a part of the resin penetrates easily into the chips and ithinders the swelling properties of board, and when panel is .made of thick chips this anti-swelling efficiency appears markedly.901.0 "o 30••o. WOlter Thickness %Expi'inslon Absorption of Chips 700"'. 0.2 m7/JFffect of moisture conte.nt of chips onwater absorption and thikness recoveryof panel.242fT%Fig 4.Ii:: 22.~'f.i.20~78<Il't 76~~ 7472RelCitiveViscosity40.65.22.2Effect of density and viscosity ofresin on water absorption andthickness recovery of panel.(thickness of chip : 1.0 mm)Den$ityA 50 %B 3'>C 203540 ...----,------------....,%% 90Fig 3.;:0,'-.--J~:;-'--6+--~*"7 --S*"·--9-;;----,7~O--7~7%Resin content70 72 14 76 78 20 22 24 26 28 30 32 %Moisture content ofchips2. Effect of pressing conditions on swelling properties of chipboard.The moisture content of chips was found to have a pronounced effect on the swell-ing properties of chipboard and the data were presented in Fig. 4. From this figure,thickness recovery and water absorption of panel decrease in proportion to the increaseof moisture content.This result is unreasonable in the viewpoint of mechanism of adhesion, but it may beconsequent on the increase of plasticity of the wet chips.Fig. 5 and 6 show the relation between applying pressure, thickness recovery andwater absorption of chipboard in each resin content. In these cases the rate of waterabsorption decrease uniformly with increase of pressure, while the rate of expansion inthickness shows the curves which are maximum at the pressure of 15 or 20 kg/cm2•The relations of specific gravity with the rate of water absorption and thickness reco-very of panel are presented in Fig. 7 - 8.According to these figures, plots of the rates of water 'absorptions and specific gravities- 55-WOOD RESEARCH NO. 15 (1955)Effect of applyingpressure on waterabsorption andthickness recovery ofpanel. (thickness ofchip: 0.2 mm)Fig 5.%10072076%32 ~09\ /'.30 '6~i':'28 \\>~, /x ,'" 08 "./i" x626 /\0 " 0~24 '~y~0/?:''~:~ . -;I".",., "'~~~.~~:-t::::20 '0.~)(. ... ...... ",/K 06.1:. - , -', ·",o-._5.!:.~n_~'bntent52% 878 Ao#x 110 " ••_ 0 '-----••::-_ •':'" Water "'" 6""=.:----';_0__ 8 ----------0..~I Absorption ··-'b.__~~~------------__ 0".. ·----)~--9.-5- .. z .,e=t--~~--:!:--*,"-~---~!:- * "';;~~_*....I20, 'i 10 75 20 30 40 k'jlcm> 60Applying pressure39 09%%760 !':.~741) 'it~, 72C .:Q'I;)lC'() ~""80~6020lCl(lC----~-:::: ......~--.79 ~35 o,B-(otC,o'(I'IJ.'1\\ '(-,,,,-,,1/=31 47 \0, "\0'\, '~ \ '",''' )( JC~ :>: 6, ' eo",/e "Bo ~ ..." .....---.------ _;;;l 21 06 <tr q, ra ><:;:.. -.: i.{ \~~-"~~,, "V1 "'- ,."/"-0-0 'a'- .!<s 0'Il &j "b., ....... -- .§,23,.\2 /J! --' _ 0 --. ':... :-.fr- ----0-~ e /./"" ' -••-.6-- ..__" 9.5-----• Water absorption --------..:---_. 0toX , •Xl(Effect of applyingpressure on thewater absorptionand thickness reco-very of panel.(thickness of chip: 1.0 mm)Fig 6.70 20 30Applyin9 pressure40,Fig 7. Relation of specific gravity:towater absorption and thicknessrecovery of panel. (thickness ofchip: 0.2 mm)0.90.5 0.6 0.7 0.8Specific ~vity,of panelFig 8. Relation of specific gravity to waterabsorption and' thickessrecQvery ofpanel. (thickness of chip: ~.O mm)%72010_~ ~_~~_--;:~_--!~_~:-'as Q6 0.7 0.8 0.9 1.0.SpecifiC ~TQvity, (If prmel30%~,~75- 56-T. MAKU and R HAMADA : Studieson the chipboardof chpboard fall on a straight line, on the other hand the relation of the rate of expan-sion to the specific gravity is shown as the curves as in the case of Fig. 5 and 6. Howe-ver, these data vary greatly depending on the moisture content of the chips before press-ing, and Fig. 9 shows an example about the relation between moisture, content, applyingpressure and thickness recovery of chip. As the results of these figures, in case of highmoisture content, not only the rate of expansion becomes small but also applying pre-ssure wh;ch shows the maximum thickness recovery removes to the side of low pressure.Fig 9. Effect of applying pressure and moisture content on thethickness recovery of panel.•0.2--0-.Noistilleconte,lt Thickness ofCIIlps-~ ~~D % 7,Omm-e- 0.2.•_~. 21 % 7,0,/t>-_~"" -'-:-"o~lIll:::''---- --:--A" ....-A-- 6- ~ _l, ,..0...., rt# "',,- '",0' 0 " ..................... 00--__•------~---._-._----.....----0702872~ 24-',C>.~~20Cl)'t~ 76&!10 .20 30 40 50 60, Applyini) ' pressure70The similar experiment was ,made for the relation between applying presure,rate ofcompression and thickness recovery of Japanese cypress (HINOKI) sliced veneer. (Fig. 10,....., 11)Fig 10. Relation between applying pressure and therate of compression in thickness of Japanesecypress (HINOKI) sliced v~neer.10 20 '30 40 50 60 70 80 ks/cm2 lQOApplyin:J pressureIn these cases the curves of, thickness recovery of veneer resemble well to the curves- 57-WOOD RESEARCH NO. 15 (1955)Fig 11 Relation of applying pressure the thickness recovery and waterabsorption of Japanese cypress (HINOKI) sliced veneer.%r----:------......--....:..--'----------,1009080~70~ .~~ 6070of compression, and are also affected markedly by the moisture content.From these results, the authors suppose that the swelling properties of chipboard areconsequent on the thickness recovery of the chips which are compressed greately in hotpressing.III. SummaryThe experiments on the effect of binder and pressing conditions on the swelling pro-perties of chipboard were performed, and the results are as follows;1. Effect of curing method of urea formaldehyde resin on the swelling properties ofchipboard was nbt remarkable, but good result ·was obtained when urea resin hadmuch methylol group.2. The density or vis:::osity of urea resin before spraying was found to have no effecton the swelling properties of panel when it was made of thin chips, on the contraryincase of thick chips thickness recovery and water absorption of panel increased byincreasing of viscosity or density ·of resin.3. Moisture content of chips was found· to have a pronounced effect on the swelling. properties of panel, that is, with increasing of moisture content of chips the dimen-sional stability of chipboard increased.4. Thikness recovery and water absorption of chipboard are greatly influenced by apply-ing presure or specific gravity of panel, and these inclinations are resemble to thethickness recovery of Japanese cypress sliced veneer when it is compressed by hotpress.~ 58-T.MAXUandR.HAMADA :Studiesonthechipboard摘 要尿素樹脂を結合剤としてチップ ･ボードを製造し､樹脂の製法と添加時に於ける濃度及び粘度,削片の含水率,圧締九 比重等が′その吸水性,膨潤性に与える影響について実験を行い大略次の如き結果を得た｡1. チップ･ボ-ドに於いてはチップ表面に於ける結合剤添加量が極めて少量であるために結合剤は出来るだけ木材に対する親和性の大な畠ことを必要とする｡ 例えば尿素樹脂の縮合に際して使用するホルムアルデヒドは尿素 1モルに対して2乃至2.5モル程度が良く,2モル以下のモル比に於いては樹脂添加量に関係なくチップ･ボードは常に大なる膨潤率を示した (第 1図)｡2. 樹脂液の濃度及び粘度がチップボードのスクビリティーに与える影響は顕著ではないが厚さの大なるチップを原料とするチップ･ボードにおいては低濃度の樹脂液を庭用した場合∴スクビリティ-が増加することを認めた (粛 2,3図)3. チップの含水率とチップ･ボードの吸水膨潤率の関係は内部膨れを生ぜしめない範囲内に於いては略々直線的関係にあり含水率の増加に伴い吸水率,膨潤率はともに減少する (第 4図)｡ かかる傾向は接着に於ける好適含水率に相反することであり,この原因は前述の低濃度樹脂に於けると同様チップの可塑性の増加及び尿素樹脂の7.ンティ子ウェ リング ･エフイシェ-/シイに基 くものと考えられるが更に検討を必要とする｡4. 成板時に於ける圧締力叉はチップ･.ボードの比重とその吸水,膨潤率は常に直線或は曲線的関係を示し (第 5-8図), 両もこの傾向はチップ含水率の増減によって著しく変化した (第 9図)｡ 亦,同様の測定をヒノキ単校について行いその膨潤率と圧縮率が同様の傾向示し,且つ著しく含水率の影響を受けることを認めた(舜10-11図)｡これらの結果よりチップ･ボードの厚さ方向に於ける膨潤性は圧縮されたチップの復元性に起因するものと考えられる｡-一･59Lr

Studies on the chipboard : Part 2. Swelling properties of chipboard

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Studies on the chipboard : Part 2. Swelling properties of chipboard

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