Cdng nghiep rirng
ANH HU^OfNG CUA TY SUAT N^N DEN MOT SO
TINH CHAT CUA GO KEO LAI, T H 6 N G N H I T A VA BACH DAN URO XU^ LY B A N G PHUCfNG PHAP NHIET - CO
Pham Van Chuffng\ Vu Manh Tudug^, Nguyin Trong Kien^, Le Ngoc Phudc'*
'-^-^-^Truang Dai hgc Ldm nghiep TOMTAT
Xir ly g6 theo phuong phap nhiet - co nham cai thien mgt so tinh chdt vSt ly, c a hoc va dp ben tyr nhien cua go, Trong nghien cuu nay chiing toi da tiSn hanh xii ly 03 loai go rimg fr6ng ph6 bi^n a Viet Nam: Keo lai {Acacia mangium x Acacia auriculiformis), Bach dan Uro {Eucalyptus urophylla) va Thong nhira {Pinus merkusii). Cac mlu g6 dugc gia cong ven kich thuoc 400 (1) x 120 (w) x chieu day (t) mm. Qua trinh hoa deo va nen ep dugc thuc hien tren may ep nhiet BYD 113/4 vcri 5 mirc ty suit nen: 10%, 20%, 30%, 4 0 % va 50%. Kgt qua nghien ciiu cho thay: Vai cung mot ch£ dp nen ep, ty suat nen anh huang ro net den dp dan hoi tra lai cua go (dp dan h6i tro lai lan nhit d6i voi g6 Bach dan va nho nhat doi vai go Thong nhua); khoi luong the tich, do ben uon ttnh va mo dun dan h6i ciia go tang khi ty sudt nen tang. De dat dugc yeu cau ciia gB nhom III theo TCVN 1072-71, voi go Keo lai ty sudt nen phai Ion htm 30%, voi gS Bach dan ty suat nen Ion han 20% va vai go Thong nhita ty sudt nen lan han 40% mai dat yeu cau.
Tir khoa: Baich d a n , Keo lai, Thong nhijra, ty suat nen, x ^ ly nhiet - co'.
1. DAT VAN DE
Trong cong nghe nen go noi chung, ty suat nen (Compress Ratio - CR) la mpt dai luang duQfc tinh bang ti le phan tram (%) giija the tich/chieu day cua go bi giam di do nen so vai the tich/hoac chieu day cua go truac khi nen.
Trong cong nghe nen go, khi nen vai ty suat nen Ichac nhau se cho san pham go nen co chat lugng khac nhau. Tren the giai da co nhieu nghien cuu ve anh huang cua ty suat nen den chat luang go trong qua trinh xu ly.
Buan Anshari et al. (2010) da nghien cijru anh huang cua ty suat nen den tinh chat co hoc cua go Tung tuyet {Cryptomeria japonica D.
Don). Tac gia da thuc nghiem vai 4 miic ty suat nen 33%, 50%, 67%, va 70%. Cac mhx yeu cau khong c6 mat, khong khuyet tat va dugc nen theo phuang xuyen tam. Qua trinh nen ep dugc thuc hien theo 3 buac nhu sau:
- Lam nong truoc: Truoc khi nen ep cac mau dugc lam nong trong mat ban ep d^n nhiet dp mong muon la 130°C, trong khoang thai gian mpt gia.
- Nen ep: Mau dugc nen ep cho &ku khi dat dp day tuong ung vai cac muc ty suit nen.
Duy tri ap luc ep trong 30 phut truac khi giai doan lam mat.
- Lam mat: Mlu ep dupe lam mat bSng he thong tuan hoan nuac trong ban ep va tiip tuc duy tri ap suat va dp day muc tieu tren mau vat de giam nhiet dp xuong den nhiet dp phong.
Thai gian lam mat khoang tir 1,0 giof den 1,5 gia.
Tu ket qua nghien cuu, tac gia da dua ra mpt so ket luan sau:
Khoi lupng the tich ciia go nen tang voi su gia tang ty suat nen. Khoi lugng the tich trung binh tang ISn lugt la 25%, 75%, 175% va 261% tuong ling voi CR la 33%, 50%, 67% va 70% so voi mau doi chiing.
Ty suat nen anh huong khong ro net den do am ciia go sau khi nen. Vai cac miic 50%, 67%
va 70%), dp am thuc te sau khi ep la 5,2%, 5,4% va 4,2%.
Gia \x\ cua mo dun dan hoi theo huang dgc tho tang len dang ke vol su gia tang ty le nen.
Gia tri mo dun dan hoi cao nhat dat toi 33 GPa theo huang dgc tha vai CR bang 70% va MC bing 12%. Gia tri mo dun dan hoi huang tiep tuyen tang dang ke khi tang ty suat nen va gia tri lan nhat la 3000 MPa a CR bang 70%. Tuy nhien, gia tri mo dun dan hoi huong xuyen tam cua g6 nen tuang iing vai CR la 33, 50 va 67%
thap ban so vai go khong bi nen ep, tni truong hgp vai CR b3ng 70% (Buan Anshari et ai.
(2010).
Youke Zhao et al. (2015) da nghien ciiu anh huang cua ty suat nen den do im cua g6 sau khi nen. Tac gia da nghien ciiu vai 02 loai g6 la Duong {Populus tomentosa) va Sa moc {Cunninghamia lanceolata); cac mau co kich thuoc 100 mm x 50 mm x 30 mm. Cac miic ty TAP CHI KHOA HOC vA CONG NGHE LAM NGHIEP SO 1 - 2019
Cong nghigp rirng suat nen la: 10, 20, 40, 50 va 60%.
Dp am truac va sau nen a ti le nen khac nhau cua g6 Duong giam tu 173 xuong 65% va Sa mpc giam tu 244 xuong 68%. Tac gia ciing chi ra rang su khac biet dp am giiia truac va sau khi nen tang dan dan vai su gia tang ty le nen. Ty le nen cao lam giam thS tich cua Imnen Ion han, noi hau bet nuac dugc giir trong g6.
Ap suat da trof thanh dpng luc day nuac ra khoi go. Doi vai cay Duong, nuac tu do chu yeu dugc luu trir trong lumen cua mach go. Doi vai cay Sa mpc, nuoc tu do chii yeu dugc luu trii trong cac quan bao. Su tham nhap cua nuac xay ra chii yeu a cac kenh dan dpc theo chieu dpc sgi go. Viec thoat nuac co xu huong lam giam su chenh lech ap suat giiia nuac trong g6 ben trong va nuac xung quanh, trong khi nen lien tuc lam tang su khac biet nay. Do d6, vai sir gia tang ty suat nen lam cho dp am gd cang giam.
Meng Gong et al. (2006) da nghien ctru ty suat nen toi da doi vai go Thong trang {Pinus strobes) va go Linh sam {Abies balsamea).Tac gia da nit ra mot so ket luan sau: (1) Ty le nen anh huang lan han den tinh chat cua go Thong va Linh sam so vdi anh huong ciia nhiet dp. (2) Nhiet dp CO anh huang dang ke nhat den tai trpng khi gia tai trong qua trinh nen. (3) Dp dan hoi tro lai cua go nen tang len theo ty suat nen va nhiet dp. (4) Nhiet dp cao ho trg lam mem go nhanh ban. (5) Cac vet mit gay va vet mit xuat hien trong mau nen, tham chi a ca ti suat nen la 5% va a nhiet dp thuang. (6) Ty le nen toi da cua go Thong trang va go Linh sam khoang 60% a dieu kien bao hoa nuac va nhiet dp ep len tai 90°C.
Kristiina Laine et al. (2013) da nghien ciiu anh huong cua ty suat nen va thai gian nen ep den dp Cling tinh, dp dan hoi tro lai va cau tnic cua go Thong (Pinus sylvestris L.).Tac gia da ket luan: (1) Ty suat nen va thai gian ep sau nen (khi nen a nhiet dp HO^C) anh huong ro ret den cau tao va tinh chat cua go Thong. (2) Khi ty suat nen va thai gian xu ly tang, ton that khoi lupng cua go tang. (3) Dp dan hoi tra lai cua go giam khi tang ty suat nen va vai cimg mpt ty suat nen dp dan hoi tro lai cua go giam khi tang thai gian xu ly sau ep. (4) Dp ciing tinh cua go tang khi tang ty suit nen, dp ciing
tinh ctia go Thong dat trj so cao khi nen ep go a miic ty suit nen 50 - 60% va thai gian xu ly la 4 gia.
Pham Van Chuang va cpng su (2014) da nghien ciiu anh huong ciia ty suat nen den mpt so tinh chat ca, vat ly chii yeu cua go Tong qua sii {Alnus nepalensis). Tac gia da ket luan: (1) Anh huang ciia ty suat nen den khoi lupng the tich quan he theo ty le thuan. Khi so sanh vai tieu chuan phan loai go Viet Nam theo tinh chit CO ly (TCVN-1072-71), ty suit nen 35%
go CO khoi luong the tich hrang duong go nhora 111. Khi ty suat nen 45% go dat khoi lupng the tich g6 nhom II; (2) Dp ciing be mat, mo dun dan hoi uon tmh, dp ben uon ttnh, dp ben nen dpc tha ty le thuan vai ty suat nen va khoi lupng the tich go sau nen. Ty suat nen 25% dp Cling be mat 76,5 MPa; mo dun dan hoi uon tTnh 6,90 GPa; dp ben uon tinh 78,7 MPa, dp ben nen dpc tho 38,4 MPa. Khi ty suat nen 35%, dp ciing be mat 82,0 MPa; mo dun dan hoi uon tinh 7,26 GPa; dp ben uon tmh 88,3 MPa, dp b^n nen dpc tha 42,3 MPa.
Khi ty suat nen cao nhat 45% dp cung be mat 84,7 MPa; mo dun dan hoi uon tinh 7,79 GPa;
dp ben uon tinh 93,4 MPa va dp ben nen dpc tha 44,4 MPa.
Nguyen Minh Hung (2016), da nghien ciiu anh huang ciia nhiet dp va thai gian ciia giai doan on dinh kich thuac den tinh chat ciia go nen chinh hinh. Ket qua nghien ciiu da khang dinh; Khi nhiet dp tang, dp dan hoi tro lai cua go giam va kha nang chong truong no (ASE) tang. Dieu do co nghia la dp on djnh kich thuoc tang khi thai gian xu ly tang. Qua trinh thay doi cac tri so ciia ham muc tieu dugc xac dinh ro net trong giai doan xu ly tii 0,5 - 4,5 gia. Khi thai gian xii ly lan hon 7,0 gio, kh6i luong the tich cua go giam dang ke. Khi nhiet dp xu ly dat toi 200*'C, dp on dinh kich thuac la toi uu nhat. Khi tang nhiet dp, khoi lugng the tich ciia go giam va mot so tinh chat co hpc ciia go Cling giam, tuy nhien tri so dp ben co hpc van cao ban so voi go khong xir ly. Dp ben nen ngang tha giam ro net nhat trong giai doan xir ly tir 0,5 - 2,5 gio; sau 2,5 gia anh huang nay khong ro net va dat gia tri on djnh trong khoang thai gian 6,5 - 8,5 gio.
Tir cac ket qua nghien cim trong va ngoai T^P CHI KHOA HOC VA C 6 N G NGHE L A M NGHIEP SO 1 - 2019
Cdng nghiep rimg
nuoc ve anh huang cua ty suat nen den chat lupng go nen, cho thay: (1) Chua co cong trinh nao nghien cim ve anh huang cua ty suat nen den chat lugng go Keo lai, Bach dan uro va go Thong nhua; (2) Xir ly go bang phuang phap nhiet - ca de nang cao dp ben co hpc ciia go la mpt giai phap khong sit dung hoa chat; (3) Ty suat nen anh huang den cau tao va tat ca cac tinh chit ciia g6, do do, tuy thupc vao muc dich su dung san pham de lira chpn miic ty suat nen phu hgp; (4) Nhiet dp go nen va dp am go anh huang ro net toi miic dp tang ty suat nen va tai mirc dp gia tai khi nen ep; (5) Xii ly nhiet cho go sau khi nen (thuc hien tai ban ep) c6 tac dung lam giam sir dan hoi tro lai cua go sau khi nen.
Trong nghien cim nay, can cii vao loai go, muc dich sir dung san pham (lam do mpc va van san chat lugng cao), chung toi tien hanh thuc nghiem vai cac miic ty suat nen la: 10%;
20%; 30%; 40% va 50%.
2. PHlTONG P H A P NGHIEN CUU 2.1. Vat lieu va thiet hi
Logi go:
Keo lai {Acacia mangium x Acacia auriculiformis): 8 tuoi, khai thac tai huyen Yen Thuy, tinh Hoa Binh.
- Bach dan {Eucalyptus urophylla): 8 tuoi.
khai thac tai huyen Thanh San, tinh Phii Thp.
- Thong nhua (Pinus merkusii): 25 hioi, khai thac tai huyen Yen Th8, tinh Sic Giang.
Chudn bi mdu go thi nghiem
Mau go thi nghiem diing cho nghien cuu dupe chuan bi qua cac buac sau day:
1) Tinh toan chpn du s6 lugng mau can thiet de chpn van xe, van sau khi chpn song duac say hong phai tu nhien dk dat dp am 35±5%.
2) Kich thuac phoi: 400 (dpc tha) x 120 (tiep tuyen) x t (xuyen tam), (mm). Chieu day (t) se tinh toan dua tren ti suat nen va chieu day san pham go nen (chieu day san pham g6 nen la 20 mm). Vai ti suat nen danh nghTa chpn truac la 10%, 20%, 30%, 40% va 50%, tinh duoc chieu day phoi danh nghia ciia mau tuong ling la 22,2 mm, 25,0 mm, 28,6mm, 33,3 mm, 40,0 mm.
Mdy ep:
May ep nhiet thi nghiem BYD 113/4 co nhiet dp ep Ion nhat la 300''C dugc gia nhiet bang dien, ap suat dau max 2400 kgf, kich thuoc ban ep 80 x 80 cm^, dugc dat tai Xuang thuc banh, Trung tam Thi nghiem va Phat triin cong nghe, Vien Cong nghiep go.
Trong qua trinh ep da sir dung thanh cu sat vuong dac c6 chieu day 20 mm de khdng che chieu day go nen.
,y^n xe xuy6n tam
Gia cSng vSn - Kich thuoc: 420 x 120 x day (mm)
- e § a m : 1 2 %
NSnSp - Nhiet (30: 140° C -ThM gian : 3 philt/ mm chl^u diy
- Ap suit: 3Mi=a
H6a deo gA -NhiOtaO: 160" C -Th&i gian : 0,6 phiit/ mm chi^u day
Cit va ki4m tra tinh chit g6 n^n:
-Ty suit nSn thi/c ti -Khii luang thi tich -04 aan h6i tro l$i
-BO bin u6n tTnh -OO ti^n n6n dpc
Hinh 1. Sff dS thi nghiem tao mSu g5 nen bing phirffng phap nhiet - cff TAP CHI KHOA HOC VA C 6 N G NGHE L A M NGHIEP SO 1 - 2019
Cdng nghiep rimg 1.1. PhvoTig phap nghien ciru
2.2.1. Tgo mau thi nghiem
Sa do thi nghiem tao mau go nen dugc the hien nhu hinh 1.
Birdc I: Hoa deo va xa am
- Xir ly hoa deo tren may ep: Nhiet dp ban ep 150 C, thai gian hoa deo: 0,6 phiit/mm chieu day mau.
- Nen so bp va xa am: Khi nhiet dp tam g6 dat 70*^C tien hanh nen ep sa bp voi ap suit 2,0 MPa; thai gian nen so bp 0,25 phiit/mm chi^u day, tien hanh giam ap de xa am. Qua trinh giam ap xa am dugc thuc hien voi 2 lin.
Bud'c 2: Nen ep
- Sau khi xa am lan 2 tien hanh nen ep voi ap luc 3,0 MPa t6i khi mirc dp nen dat 40%, nhiet dp ep 140'^C tai khi miic dp nen dat 40%).
Duy tri ap suat va nhiet dp do trong khoang thai gian tuang iing la 3,0 phut/mm chieu day.
- Giii van trong may ep: Giam ap luc ep xu6ng 1,2 MPa, nhiet dp I00°C, thai gian 120 phiit, sau do do van va de on dinh van.
Buffc 3: On dinh van sau xir ly
Van go sau khi xu ly nhiet - co duoc chuyen sang khu vuc on dinh nhiet, am trong dieu kien moi truang tu nhien. Nhiet dp 30±3''C, dp am tuang doi 70±5%, thai gian 7 ngay.
222. Phuffng phdp xdc dinh cdc chi tieu chdt luffng gd nen
Tinh tisudt nen thtrc te (CRu):
Ty suat nen dupe tinh theo cong thiic (1):
CR= t2Zh xWQ(%) (1)
to
Trong do:
to - chieu day mau truac khi nen ep, mm;
tl - chieu day mau sau khi nen ep, mm.
Kiem tra khoi luo'ng the tich cua go nen (y):
- Tieu chuin kiim tra: TCVN 8048-2:2009.
- Mau go: Mau go co binh dang hinh hop chii nhat vai kich thuac 20 x 20 x 20 mm; 10 mau/serie thi nghiem.
- Xac dinh khoi lupng the tich d dp am thang bang.
+ D^ mau go on dinh trong buong duong mau (Jeiotech TH-G180) diSu chinh nhiet dp 20°C, dp im tuang d6i 65%, thoi gian di 6n dinh la 20 ngay. Tien hanh can miu dS kiim tra sao cho mau go c6 khoi lugng khong d6i
hoac chenh lech khong qua 0,01 g sau 2 lan can lien tiep, luc nay mau da a trang thai can bang.
+ Do kich thuoc mau go a dp am thang bang tinh Vtb (cm^).
+ say mau go den trang thai kho kiet, can mau dugc khoi lugng mtb (g).
+ Tinh khoi luong the tich theo cong thiic:
y=~>-^ (2) Trong do:
y - khoi lupng the tich go, g/cm ; m,b - khoi lugng go kho kiet, g;
Vtb" the tich go a dp am thang bang, cm . Tinh do ddn hoi tra lgi:
Dp dan hoi tra lai cua go nen la mpt chi tieu quan trpng de danh gia cong nghe nen go. Co nhieu phuang phap xac dinh dp dan hoi tra lai nbu: ngam nuac, lupc, de trong khong khi.
Trong nghien ciiu nay, dp dan hoi tra lai ciia go nen dugc xac dinh sau khi mau go nen de on dinh trong buong duong mau (Jeiotech TH- G180) CO nhiet dp 20°C, dp im Urang d6i 65%, thai gian de on dinh la 20 ngay.
Dp dan hoi tra lai dugc tinh theo cong thiic sau (Seborg, R.M; Millet, M.; Stamm, A.J, 1945 va Stamm, A.; Millet, M., 1948):
RS = ^ X 100 (%) (3) Trong do:
RS - dp dan hoi tro lai, %;
to - chieu day mau kho kiet truac khi nen, mm;
tl - chieu day mau sau khi nen, mm;
t2 - chieu day mau sau khi de on dinh, mm.
Xdc dinh do ben udn tinh (MOR) Tieu chuan kiem tra: theo tieu chuan qu6c ti ISO 3133:1975 va ISO 3349:1975 (TCVN 8048-3:2009).
Kich thuac mlu: 20 x 20 x 300 mm.
Dung lupng mau: 30 mau/serie/loai g6.
Dung cu kiem tra: Thuoc kep dp chinh xac 0,01 mm, may thir tinh chit ca ly QTEST25.
Quy trinh kiem tra: Mau sau khi gia cong xong xu ly mau den dp am can bang voi moi truang khong khi thuang (12%). Khi mau da xu ly ve dp am thang bang tien hanh do kich thuac mau sau do tien hanh xac dinh giai han ben nen dpc dugc thuc hien tren may thir ca hpc QTEST25.
Cdng nghiep rimg
Cong thirc xac dinh dp ben uon tTnh:
MOR = ^ ^ ^ , MPa (4) Trong do;
Pmax - lyc pha hoai mau, N;
1 - khoang each goi, mm;
w, t - chieu rpng va chieu cao mau, mm.
Xdc djnh do ben nen dgc tha (CS):
Tieu chuan kiem tra: tieu chuan quoc te ISO 3132-1975.
Kich thuoc mau: 20 x 20 x 30 mm.
Dung luong man: 30 mau/serie/loai go.
Dung cu kiem tra: Thuac kep dp chinh xac 0,01mm, may thir tinh chat co hpc QTEST 25.
Quy trinh kiem tra: Mau sau khi gia cong xong xii ly mau den dp am can bang vai moi truang khong khi thuong (12%). Khi mau da xir ly ve dp am thang bang tien hanh do kich thuac mau sau do tien hanh xac dinh giai ban ben nen dpc dugc thuc hien tren may thir ca
^ Bang 1. Ket qua kiem
hpc QTEST 25.
Cong thiic xac dinh:
CS= -^,MPa (5) axb
Trong do:
P - lire pha buy mau, N;
a - chieu rpng cua mau, mm;
b - chieu rpng mau, mm.
2.2.3. Phuffng phdp xir ly sd lieu
Trong nghien ciiu sii dung phan mem Microsoft Excel de tinh toan gia tri trung bmh m i u va dp lech chuan.
3. KET QUA VA T H A O LUAN 3.1. Ti s u i t nen thye te va ti suat nen thi^t ke cua go nen
Cac m i u go dugc nen vai ty suat khac nhau sau khi de on dinh dugc tien hanh kiem tra ty suat nen thuc te so vai ty suat nen thiet ke. Ket qua dugc the hien nhu bang 1.
tra ty suat nen thuc te TT Ty suat nen
thiit ki (%)
Ti suat nen thuc te (%)
Keo lai Bach dan Thong nhua
TB Sd
1 2 3 4 5
10 20 30 40 50
8,3 18,9 28,2 37,4 46,2
1,3 0,7 0,9 1,2 2,3
6,6 16,0 24,3 34,6 43,5
1,2 1,0 0,7 1,6 1,9
9,3 19,1 27,7 39,1 48,3
0,6 0,6 0,9 0,3 1,1 Ghi chii: TB - Gid tri trung binh: Sd - Do lech chudn.
Ket qua nghien ciiu a bang 1 cho thiy, ty suat nen thuc te cua tat ca cac che dp deu nho ban ty so nen thiet. Nguyen nhan ciia hien tupng nay; Trong qua trinh nen ep, go a trang thai dan deo, the tich cac vung rong trong g6 giam. Ket thiic qua frinh nen ep, lupng khong khi trong go dang 6 trang thai ap suat cao se thoat ra ngoai lam cho g6 bi gian na. Vai g6 Thong nhua thi ti suat nen thu dugc la cao han Bang 2. Khoi luffng the tich cua mau
so vdi hai loai go con lai. Go Bach dan co ti suat nen thu dugc thSp hon. Hay noi each khac, hieu qua thu dugc theo thiet ke cua go Thong nhua la tot nhat.
3.2. Anh huo^g cua ti suat nen den khoi lutfng the tich cua go nen
Khoi lupng the tich cua go nen a dp am 12% vai ti suat nen thiet ke khac nhau the hi?n trong bang 2.
gh vol ti suit nen thiit ke khac nhau _ TT Ti suit nen
thiet ki (%)
Khoi lugmg the tich, do im 12% (g/cm^)
Keo lai Bach dan Thong nhua
TB Sd
1 2 3 4 5
10 20 30 40 50
0,601 0,660 0,712 0,763 0,811
0,022 0,012 0,015 0,020 0,038
0,673 0,732 0,784 0,849 0,905
0,023 0,019 0,013 0,030 0,036
0,656 0,715 0,766 0,835 0,890
0,011 0,011 0,016 0,014 0,020 92 TAP CHi KHOA HOC VA C 6 N G NGHE L A M NGHIEP SO 1 - 2019
Cdng nghiep rirng Go sau khi nen vai ti suit nen tu 10 - 50%
CO khoi lugng t h i tich b i i n dpng rit lan va theo quy luat rat ro ret. Khi ti suat nen tang len, khoi lugng the tich cua go nen tang len. Kit qua nay hoan toan phu hgp, do go sau khi nen CO mat do vat chat cao, dp rong giam xu6ng
M^ch g6 b| n6n
nen khdi lugng the tich tang len. Tuy nhien, vai 3 loai g6 thi nghiem, ket qua khoi lugng t h i tich cua g6 tang khong gidng nhau, do cac loai go khac nhau co dp dan hoi tra lai sau khi nen khac nhau nhu da phan tich o tren.
Jnx(TC khi ndn
Mat cat ngang cua go Keo
Sau Mil nto (Ti sudt n6n 40%)
nen Vong nam go Thong nhua truac va sau khi nen Hinh 2. Mat cat ngang cua go nen
Voi go Thong va go Bach dan, do ban than go CO khoi lugng the tich cao nen khi nen vai ti suat nen 20 - 30% da co ban dat dugc khoi lupng the tich cua go nhom HI theo TCVN 1072-71. Tuy nhien, day mai la mpt cbi tieu, do do chua the khang dinh go da dat tieu chuan go nhom III theo each phan loai nay.
3.3. Anh h u o n g ti s u i t nen d§n dp dan hoi trd' lai cua go nen
Khi nen ep go a trang thai dan deo, ket thiic qua trinh nen ep ben trong go van ton tai mpt lugng am va mpt lugng khong khi d trang thai ap suat cao do do mau go luon co xu huang trd lai trang thai ban dau (nguyen trang). Dp dan hdi trd lai ciia gd phu thupc vao loai go, ty suat nen, che dp nen ep, dp am go... Dp dan hdi trd lai cua gd vdi cac miic ty suat nen khac nhau dugc the hien nhu bang 3.
Bang 3. Do dan hoi tru lai ciia mau go voi ti suit nen thiet ke khac nhau TT
1 2 3 4 5
Tl suat nen thiet ki (%) -
10 20 30 40 50
TB 1,7 1,1 1,7 2,5 3,6
Keo lai Sd 0,5 0,1 0,2 0,2 0,3
D6 dan hSi trff tai (%) Bach dan TB 3,2 3,8 5,4 5,1 6,2
Sd 0,3 0,4 0,7 0,5 0,4
Thong nhua TB Sd 0,7 0,1 0,9 0,1 1,2 0,4 1,9 0,3 2,6 0,5 Vdi ty le dan hdi trd lai khi kiem tra ddi vdi
3 loai gd nen cho thay, ti le dan hdi trd lai sau khi de dn dinh la rat thap, chi dudi 4% vdi go Keo lai va go Thdng, con dudi 7% vdi gd Bach dan uro. Dieu nay cho thay, viec nen gd Bach dan se khd ban so vdi hai loai gd cdn lai. Su khac nhau v i ty le dan hdi trd lai cd the do su khac biet ve cau tao giiia cac loai gd gay ra.
Ciing tir k i t qua nghien ciiu cd t h i thiy, khi tinh toan thiit ke thi nghiem hoac san xuit gd nen tir cac loai go khac nhau se can xac dinh ti
suat nen danh nghia va chieu day phoi danh nghia khac nhau de thu dupe go co ti suat nen va chieu day san pham theo yeu cau.
Sd lieu thi nghiem c6 the lam can cii de tinh toan lugng du chieu day can thiet khi tinh chieu day phdi ep.
3.4. Anh h u o n g cua ti suat nen den do ben uon ttnh ciia go nen
Dp ben udn tmh cua gd d cac miic ty suat nen khac nhau dugc the hien nhu bang 4.
Cong nghiep rung
Bang 4. Bo ben uon tTnh cua mau g6 vol ti suit nen thiit ke khac nhau Ti suat nen
thiet ke (%)
D6 ben uon tinh (MPa)
Thong nhua Sd 1
2 3 4 5
10 20 30 40 50
83 92 99 106 113
7 4 5 6 5
94 102 109 118 126
6 5 4 4 5
68 74 79 86 92
3 3 4 2 5 Dp b i n CO hpc cua gd tang khi khdi lugng
thi tich (mat dp ciia go) tang; khi tang ty suat nen da lam cho the tich cac khoang trong trong go giam va neu vach te bao sgi gd khdng bi tdn thuang la nguyen nhan tang dp ben ca hpc
Tir ket qua thi nghiem cho thay, vdi go Keo lai va gd Bach dan uro cd the chi cSn nen vdi ti suit nen tir 20% da dat dp ben udn tinh cua gd nhdm III theo TCVN 1072-71, my nhien, vdi gd Thdng nhua, phai nen vdi ti suat nen khoang 50% mdi dat yeu cau.
Day se la can cir quan trpng trong viec lira chpn thdng sd cdng nghe tdng quat de dua vao thuc tien san xuat vdi yeu cau san pham dau ra cho timg loai san pham go nen tit cac loai go khac nhau.
3.5. Anh h u ^ g ciia ti s u i t nen den do ben nen doc cua go nen
De ben nen dpc thd la mdt chi tieu quan trpng danh gia chat lugng gd, ket qua ve anh hudng ciia ty suat nen den dp ben nen dpc tho cua cac loai gd dupe the hien nhu bang 5.
Bang 5. D6 bin nen doc cua mJu g5 vol ti suit nen thiet kg khac nhau TT
1 2 3 4 5
Ti suat nen thiStlt6(%) -
10 20 30 40 50
TB 43 48 51 55 58
Keo lai Sd
5 3 4 5 4
Do ben nen doc thff (MPa) TB
53 58 62 67 72
$ach dan Sd
4 4 3 3 3
Thong nhira TB Sd 32 3 35 3 37 4 40 2 43 5 Tuong tu vdi dp ben udn tTnh, dp ben nen
dpc thd gd cua 3 loai gd nen chiu anh hudng dang ke bdi ti suat nen thiet ke. Khi ti suat nen tang len thi dp ben nen dpc thd tang theo.
So sanh vdi yeu ciu trong TCVN 1072-71 ta thay, gd Keo lai va Bach dan chi cin nen vai ti suat nen khoang 20% da dat yeu ciu, nhung vdi gd Thdng nhua thi phai nen vdi ti suit nen 50% mdi dat yeu cau.
4. K E T LUAN
Ti suat nen thiet ke cd anh hudng ro ret d i n tinh chat cua san pham gd nen tir 3 loai go lua chpn. Khi ti suat nen thiet k i cao thi ti suit nen thuc te thu dugc dat miic dp cao ban so vdi ti
suat nen thiet ke thap, do miic dp dan hoi trd lai ciia gd nen vdi ti suat nen cao thap ban.
Khi ti suat nen tang len, khdi lugng the tich va dp ben c a hpc ciia gd tang theo. Vdi khoi lugng the tich, quy luat bien ddi ca ban theo ti le thuan, tuy nhien vdi dp ben udn tinh va do b i n nen dpc thd thi cd the tang theo mot quy luat khac. Miic dp tang cham ban so vdi khoi lugng the tich cua gd nen.
Khi nen gd Keo lai de dat dugc dp bin ca hpc tuang iing vdi gd Nhdm III trong TC1072- 71 thi cin nen vdi ti suit nen Idn hon 30%, ty suit nen vdi gd Bach dan Idn ban 2 0 % va vcfi gd Thdng can ty suit nen Idn hon 40%.
94 T A P C H I K H O A H O C VA C 6 N G N G H E L A M N G H I E P SO 1 - 2019
Cdng nghiep rung
TAI LIEU THAM K H A O 4. Kristiina Laine, Knstoffer Segerholm, Magnus 1. Pham Van Chuang, Vu Manh Tuong (2014). Anh Walinder, Lauri Rautkari, Graham Ormondroyd, Mark hudng cua nhiet do nen ep d6n mot s6 linh chat vat ly, Hughes, Dennis Jones (2013). Micromorphological CO hoc cua go T6ng qua sii {Alnus nepalensis). Tap chi studies of surface densified wood. Journal of Materials Nong nghiip vd PTNT, 22:12-16. Science, 49. 2027-2034.
2. Nguyin Minh Hiing (2016) Anh huong ciia nhiet 5. L. Li, M. Gong, N Yuan, D Li (2012). Recovery do va thdi gian xii ly 6n djnh kich thudc ddn tinh chk of Mechanically Induced Residual Stresses in Densified ciia gd nen chinh hinh. Tap chi Khoa hoc vd CSng nghe Softwoods Created During a Densification Process.
Ldm nghiep, 5: 110-120. Journal of Wood and Fiber Science, 44{4) 365-373.
3 Buan Anshari, Akihisa Kitamori, Kiho Jung, Tvon 6. Youke Zhao, Zhihui Wang, Ikuho Iida, Rongfeng Hassel, Kohei Komatsu and Zhongwei Guan (2010). Huang, Jianxiong Lu, Jinghui Jiang (2015). Studies on Mechanical properties of compressed wood with various pre-treatment by compression for wood drying L effects compression ratios. Conference. Internation Symposium of compression ratio, compression direction and of Indonesian Wood Research Society, At Denpasar, compression speed on the reduction of moisture content Bali, Indonesis, V o l . 2 m.-WQod. Journal of Wood Science, 6l{2): 113-119.
EFFECT OF COMPRESSION RATIOS ON SOME PROPERTIES OF DENSIFIED ACACIA HYBRID, EUCALYTUS UROPHYLLA
AND PINUS MERKUSII WOOD BY THERMO-MECHANICAL TREATMENT METHOD
Pham Van Chuong', Vu Manh Tuong^, Nguyen Trong Kien^ Le Ngoc Phuoc'*
'•-•^•''Vietnam National University of Forestry
SUMJMARY
Thermo-mechanical treatment is a method to improving durability and physical-mechanical properties of wood.
In this study, effect of compression ratios (CR) on quality of densified Acacia hybrid {Acacia mangium x Acacia auriculiformis), Eucalytus urophylla and Pinus merkusu were investigated. The samples were initially subjected to natural drying to approximately 35±5% moisture content, and then cut to the dimensions of 400 (1) X 120 (w) X different thicknesses (t) mm. The softening and compression process was performed on the heat press BYD 113/4, andthe samples were densified with compression ratios of 10%, 20%, 30%, 40% and 50%.
According to the results of this study, compression ratio clearly affects the recovery set (RS) of the wood (the largest RS for Eucalyptus and the smallest for Pinus); density, static bending strength and elastic modulus of wood increase as the compression ratio increases. To meet the requirements of group III timber according to TCVN 1072-71, with Acacia hybrid wood, the compression ratio must be greater than 30%, with Eucalyptus wood the compression ratio is greater than 20% and with the Pinus wood the compression ratio is greater than 40%.
Keywords: Acacia mangium x Acacia auriculiformis, compression ratio. Eucalyptus urophylla, Pinus merkusii, thermo-mechanical treatment.
Ngay nhan bai Ngay p h a n bien Ngay quyet dinh d a n g
24/12/2018 29/01/2019 11/02/2019
