KHOA HQC C 6 N G N G H |
IMGHIEIXI CIJU CAI THIEIM K H A MAIVG 51J DLJIMG IVGOAl TROI CLIA VAIM DAIM
BAIVIGGlAl P H A P BIEIV TilMH VOI
IVIELAIUIIV FOIVIAIMDEHYT
Tqnh Hiin Mai^
T6MTAT
Trdn the gidi da cd nhieu cong trinh nghidn cuu gd bidn tinh vdi nhira mdlamin fomandehyt, tuy nhidn, nghien cuu bien tinh van mdng bang nhya mdlamin fomandehyt dl san xudt van dan c6n rdt it va chua duoc dd cap den d Vidt Nam. Vdi myc dich ndng cao kha nSng sir dyng ngoai trdi cho van ddn san xuat tir van mong gd bd dd, da tien hanh ng^m tdm van mong ti-ong dung djch nhya mdlamin fomandehyt d cac cap nong do 10%, 15%, 20% dl tien hanh san xu§[t van dan bidn tinh. Qu^ tiinh da tu ciia nhira mdlamin fomandehyt dugc kdt hop cung vdi qud tiinh dp nhidt cCia van dan. Kit qua cho thiy: van ddn bid'n tinh vdi mdlamin fomandehyt d cac cdp ndng dd trdn it chju anh hudng ciia cdc ydu td mdi trudng ngodi trdi ddn chat lugng van hon cdc miu van ddi chung. Cu thd la: giam dp im va bidn dp thay doi dg im cua vdn, giam ty Id nam bidn mau d mat sau ciia vdn rO rdt, tang dp on dinh mau sac, giam muc dp nut trdn bd mat van, giam muc dp bong tach, bidn dang cho mSu van. Nong dp mdlamin fomandehyt tir 10-15% dam bao tdt kha nang chdng chiu cac ydu td cua m6i trudng ngoai ti-di ciia van dan bien tinh. Van dupe son phQ bd mat co kha chdng chiu moi trudng ngoai trdi tdt ban cac mSu van khong son phu bd mat.
Tu khda; Bong tach, bidn d^ng, mdlamin fomandehyt, ndm bii'n mau, nut hi mat, van dan hien tinh, yeu to ngoai troi.
LDATVANDE
Khi go vd cdc san pham tir gd dugc sir dung ngodi tidi, cdc san pham ndy chiu anh hudng ddng tiidi cda nhiiu yiu td mdi trudng nhir qua trinh quang hda gdy ra bdi dnh sdng mdt tidi; qud trinh tiiuy phdn, bdo mdn, truong nd vd co nit gdy ra bdi nude mua, suong, tuylt vd thay doi do am trong khdng khi; qud trinh biin mdu, phdn buy gdy ra bdi su xam nhdp ciia cdc loai nam... Tat ca nhirng dnh hudng tidn ldm giam khd nang vd tiidi gian sir dung ciia san pham gd (Trinh Hien Mai, 2009).
Cung nhu vdi gd nguydn, van ddn vd cdc loai san pham vdn nhdn tao dang tam khac chiu anh hudng nhanh chdng ciia cdc yiu to mdi trudng ngodi tidi.
Tuy nhien, vdn dan dd hi anh hudng bdi tiiay ddi do am mdi tiirdng hon go nguyen do moi lidn k i t bdng keo dan giira cdc ldp van mdng cd chilu tiid khde nhau. Ty Id co nit khde nhau giiia cdc ldp vdn mdng tao ndn ndi ung suat cho mdng keo, tdi mdt gidi han nhat dinh, mdng keo bj bong tdch, khi dd san pham van ddn hi phd huy (Williams, 2005).
Do dd, d l giam ede tac ddng ciia mdi trudng din gd vd cdc san pham tir gd sir dung ngodi ti-di, bidn phdp pho bien nhat la ngdn cdch b l mdt gd vdi mdi tiirdng nhu son phii b l mat. Ben canh dd, cdc giai
' Trudng D^i hgc Lam nghidp
NONG NGHIEP VA PHAT TRIEN NONG THON
phdp bien tinh gd, lam thay doi cau tiiic t l bad go, dd vd dang duge nghidn cuu, dd chi ra nhiiu kit qua kha quan cho vide ndng cao kha ndng chong chiu cdc dieu kidn mdi trudng cho gd vd cdc sdn pham tir gd bien tinh.
Trdn till gidi, nhieu cdng trinh nghidn cuu dd chung td uu diem ciia san pham gd biin tinh vdi nhua mdlamin fomandehyt nhin ndng cao kha ndng chiu nude, chiu am vd tinh dn dinh kich thudc (Inoue et al., 1993), cudng do co hgc ciia gd (MCE, MOR, do cung, ...) ciing dugc cai thidn ddng k l (Deka and Saikia, 2000). Ngodi ra, gd biin tinh vdi mdlamin fomandehyt cd khd ndng lam giam su phd buy ciia cdc loai nam muc vd nam bien mdu (Lukowsky etal., 1999; Rapp and Peek, 1996), cung nhu tdng kha ndng chdng chiu cdc diiu kidn mdi tiirdng (Kloser et al., 2009; Trinh Hien Mai, 2009). NhCmg nghidn cuu hien dai da chi ra rdng cdc phdn tir mdlamin fomandehyt cd khd ndng di chuyin vdo sdu ti-ong cau tnic gd, lidn k i t vdi nhau tao tiidnh mang khdng gian 3D tich tii tiong rudt vd vdch t l bdo (Rapp et al., 1999;
Lukowsky, 1999), ddy Id ly do cho sir cdi tiiidn cdc tinh chat ciia go biin tinh vdi nhua mdlamin fomandehyt.
Gd bd de (Styrax tonkinensii) Id loai go rimg tiong, cd phdn bd rdng d Viet Nam, vdi ddc dilm tiidn tiidng, tidn, gd mem, dd gia cdng ndn chu yeu duge sir dung d l bdc van mdng cho san xuat van dan.
KY1 -THANG 10/2011 91
KHOA HQC C b N G N G H | Tuy nhien, do go bd di dd bi sau nam i)ha hoai, dl
bi bien mau, niit ne khi de ngoai trdi, ndn vdn ddn tir gd bd dl chii yiu su dung cho dd mdc ndi thdt thdng dung. Trong khi nhu cdu sir dung go vd cdc san pham van nhan tao cho san xuat do mgc ngodi trdi d nude ta ngay cang gia tdng. Vdi muc dich nang cao kha nSng sir dung ngoai triri cho van dan tir gd bd dd, da tidn hanh ngam t;"im van mdng gd h6 de vdi dung dich mdlamin formandehyt d cdc cdp ndng dd khac nhau dl san xuat van dan bidn tinh vd danh gia cac tinh chat ciia van dan bien tinh khi su dung ngoai tidi.
D. NGUYEN L i u VA PHUONG PHAP NGHIEN CUU
1. Nguydn hdu
Gd bd de (10 tudi) sau khi xu ly nhidt, dugc bdc thanh nhung tam vdn mdng cd chilu day 1,5 mm, chieu dai 1,2 m, chieu rdng 0,6 m, vcri sai sd chilu day va kliuyet tat ciia van mdng deu ndm trong pham vi cho phep de san xuat van dan. Sau dd dugc cdt thdnh nhung tam van mdng cd kich thudc 600 x 600 X 1,5 mm\ do am 8-10%.
Hda chat bidn tinh cho vdn mdng la nhua mdlamin formandehyt (Prefere 4865) cua Cdng ty Dynea d dang bdt mau tidng, do nhdt va do pH tiong dung dich vdi nude (ty Id 1:1, d 25"C) lan lugt Id 30-40 mPa.s vd 9,4.
Chat ket dinh duge su dung de san xuat vdn dan la keo phenol formandehyt (Dynosol WG 6111) ciia Cdng ty Dynea. Do nhdt d 30°C Id 70-110 mPa.s vd dg pHd25«C la 12,9-13,2.
2. Phuong phdp nghidn cuu
Nghidn cim duge tien hanh theo phuong phap thuc nghidm, bao gom 2 ndi dung chinh: (1) san xudt van dan biin tinh vd van dan doi chimg, (2) kilm tra cdc tinh chat ciia van dan biin tinh vd vdn dan doi chimg khi sir dung ngodi tidi.
a. Trinh tu vi cic thdng sd cua qui trinh san xuat vin din biin tinh vi vin din ddi chirng
Van mdng gd bd dl dugc ngdm d diiu kidn thudng tiong dung dich mdlamin formandehyt (MF) vdi cdc cap nong do khde nhau 10%, 15%, 20%, trong thdi gian 4 ngay. Vdn mdng ngdm tiong nude (nong do MF 0%) dugc su dung dl san xuat vdn ddn doi chung. Qua trinh cdng nghd san xudt van ddn biin tinh vd van dan doi chimg sau giai doan ngdm tam tuong tu nhau.
- Sau 4 ngdy, vdt vdn mdng ra, lau sach hda chdt bdm tidn bl mdt vdn mdng, sdy vdn mdng d nhi^t dO 40''C tiong 32 gid, din khi dg dm cua vdn dat 8 -10%.
Trdng keo phenol formandehyt Idn bl mdt vdn mdng vdi lugng keo trdng 150 g/m^ dl rdo khoang 10 phut sau dd tiln hdnh ep vdn.
lip vdn vdi chi dd dp nhu sau: nhidt dd dp t = WO, dp sudt dp P = 1,2 MPa; tiidi gian Ip T =10 phiit Qud tiinh da til aia nhua MF dugc kit hgp vdi qud tiinh dp vdn.
b. Kii'm tra cic tinh chit cua vin din bidn tinh
vi vin din ddi chung khi su dicing ngoii trdi ^ San phdm vdn ddn biin tinh vd vdn dan dii chirng
dugc dl 6n djnh 4 ngdy cho do dm vdn gdn vdi di} am tiidng bdng roi gia cdng mdu theo tidu chudn EN 927-3
(2006) vdi kich thude mau: ddi x rgng x ddy = 375 x 100 X 6 (mm^). Vdi mdi cap ndng do ciia vdn dan bidn tinh va van dan ddi chimg, ta tidn hdnh phun son Idn bl mdt trude cua mau vdn: 3 mau cd bl mdt son mau trdng, 3 mau cd bl mat phii vecny mdu vdng, 3 mdu cd bl mdt dl trdng khdng son, canh ciia cdc mau van cung dugc son mdu ghi (son cua Cdng ty TNHH Duy Dat). Mdt sau cua tat ca cac mau vdn diu dl tiong, khdng son.
Sau dd tiln hdnh gdn mau Idn gia de ngoai tidi, gid nghidng mgt gdc 45° vd quay vl hudng Ddng Nam, dia dilm ddt gia dl mau tai Trudng Dai hoc Ldm nghidp tiidi gian tir 1/11/2010 din 1/5/2011
(hinh 1).
Hinh 1. Mdu vdn ddn d l ngodi trdi sau 6 thdng ^ (til trai sang phai: miu khong son be mat, mh r son bS mit mau trdng, mdu phu vecny mau vang) i^
Cdc mau vdn ddn d l ngodi trdi duge tien hanh kilm tra 1 thdng/ldn va ddnh gid tiieo ede tinh chat sau: dg dm cua mau, do thay doi mdu sdc d mdt tiudc cua mau, ty Id nam biin mau b mdt sau ciia mdu,, mire do nut b l mdt d mdt trude ciia mau, miic d^;
bong tdch, biin dang ciia mau.
KHOA HQC C Q N G NGHfi
+ Ddam cua miu vinr. duge ddnh gia tiong sudt qua tiinh phoi. Trude khi phoi mau, tien hanh do do am vd can mdu, tir dd xac dinh dugc khdi lugng khd kiet ciia mdu. Sau mdi mdt chu ky (1 thang/ lan) lai tien hanh cdn khdi lugng cua mau ngay khi vira lay xudng khdi gia, rdi tinh ra do am cua mdu, tir dd danh gid duge sir thay ddi do am cua mau tiong qua tiinh phoi ngodi tidi.
+ Do thay ddi miu sic d mit tivdc cua miu.
hang thdng, mdu dugc lay xudng khdi gia, sau khi can mdu de xac dinh do am, mdu duge de tiong bi vi khi hdu (nhidt do 20°C, dd am tuong ddi 65%) vai ngay cho do am dat tdi dd am tiiSng bdng rdi kiem tia can tiidn (scan) cd mdt trude vd mdt sau cua mau.
Dl danh gid miie do anh hudng ciia mdi trudng ngodi tidi tdi mau sdc bl mdt trude cua mau van (mdt tiep xiic true tiep vdi dnh sang mat tidi), ta danh gia qua thang do CIE L, a, b hinh anh ndi soi cat ldp mat tiirdc cua mau van bdng phan mem Photoshop 7.0.
Trong dd, L: Chi do mdu tir den den tidng theo tfiang do tir 0-256.
Tinh gid tri L* (chi sd do sang cua mau) theo thang do tir 0-100 qua cdng thiic chuyen doi:
L
V=
2.56 Delta L dugc tinh theo cdng thu:c:
Delta L = Lo*-Li*
Trong dd: LQ* Id chi sd do sang ciia mau d thdi diem bdt dau phoi mau;
Lj* la chi sd do sang ciia mau d tiidi dilm sau khi phoi mau 1 tiiang, 2 tiiang...
+ Tyle nam biin miu omit sau cua miu vin:. su dung phan mim xir ly anh GIMP dl danh gid hinh anh ndi soi cat ldp mat sau cua mau, mdu cua mau van se chuyin sang hai mdu den vd tidng nhu hinh 2.
Ty Id nam bien mau chinh Id ty Id dilm den tidn todn bd mat sau ciia mau van.
Hinh 2. Hinh anh bl mat phia sau ciia mdt mau vdn trude vd sau khi xu ly bang phan mim GIMP dl
ddnh gid ty Id nam biin mdu
+ Muc do nut be mat: Danh gia mire do nut bl mat bang mdt thudng va kinh lup xlO d mat trude cua timg mau van tiieo tidu chuan ISO 4628-4 (2003).
+ Muc do bong tach, bien dang, danh gid sd lugng mdu van bi bien dang (cong, vdnh, van, xodn...), vd bong tdch tidn canh van bdng mdt thudng.
UI. KET QUA VATHAO LUAN
1. Dd am cua mau Ban^
Loai mdu Mdu khdng
son b l mat
Mau son b l mdt mdu
tidng Mdu phii b l
mat vecny mau vdng
j l . T o n g h g p d d Ndng do MF
Ddi chirng MF 10%
MF15%
MF20%
Doi chimg MF10%
MF 15%
MF20%
Doi chimg MF 10%
MF 15%
MF20%
am (%) a i a n Thang 1
29,96 26,33 24,57 23,90 28,55 24,00 22,93 21,73 27,17 24,50 22,73 20,97
idu vdn ddn Thang2
32,60 28,53 25,20 24,17 30,07 27,70 23,93 19,50 28,03 27,77 23,73 20,90
tiong qud tri Thang3
26,27 23,27 22,77 21,13 24,80 21,90 20,70 20,17 24,27 22,30 20,47 20,23
nh 6 thdng p Thang 4
40,83 30,37 27,83 25,37 34,33 28,93 25,47 22,33 33,47 28,37 25,43 22,33
hoi ngodi tidi Thang 5
24,47 22,47 21,27 19,40 22,97 20,40 21,23 18,63 22,93 20,70 21,33 19,97
Thdng 6 35,37 30,70 27,97 25,50 33,83 28,07 25,27 22,50 32,20 28,83 24,60 22,53 Ta tiiay, d cimg mdt thdi dilm, do am cua mdu Khi nong do MF tdng tir 10% den 20%, dd am cua van van dan ddi chung ludn cao hon do am cua mdu vdn dan biin tinh giam dan. Diiu nay dugc giai tiiich do:
dan biin tinh d ca mau son vd khdng son phu bl mat. cdc phan tir MF tich tu tiong nhtmg khoang rdng cua
NONG NGHIEP VA PHAT TRIEN NONG THON - KY 1 - THANG 10/2011 93
KHOA HQC C 6 N G N G H £
cau tnic gd (rudt, vdch tl bao, khoang tidng giiia cdc so vdi vdn ddn ddi chirng. Vi vdy, vdn dan biin tinh te bao gd,..) va trong cac vet nirt tl vi (microscopic) vdi MF cd thi ban chi duge sir anh hudng do thay tien bl mat van mdng da tao tiidnh rao can ban ehl ddi dg dm ciia mdi trudng din chat lugng vdn khi sir sir xam nhap cua nude va do dm trong mdi tmmig tu dung ngodi trdi.
nhidn vao cac lap van. Khi ndng dd MP^ tAng, mire do tich tu cua MF tiong go tdng, do dd hieu qua ldm giam do am ciia van cdng tdng.
Do dm cua van ddn khdng son phu bl mat cao hon do am cua vdn dan son phu bl mdt mgt it do tdc dung ngdn cdch sir tiip xiic true tiip vdi mdi trudng ngoai tidi cua ldp son phii bl mdt.
2. Ty Id ndm biin mdu
Vl gid phoi mdu duge dat tidn nIn ddt ngoai tidi, ndn mat sau cua mdu vdn khdng dugc son phii sd nhanh chdng bj thay ddi mau bdi loai nam biin m^
(tdn klioa hgc Id Aureobasidium pullulans). Loai nam nay khdng phd hiiy cau tiiic gd, chi lam cho ldp go bl mdt cd cdc dom mdu xanh den. Bang 2 la kit qud d ^ Ngoai ra, trong qua tiinh dl ngoai trdi, bien dg gid ty Id ndm biin mdu tidn bl mdt sau cua mdu v^
dao ddng do am cua van dan biin tinh cung thap hon ddn bdng phdn mim GIMP sau 6 thdng dl ngodi tidi.
Bang 2. Tdng hgp ty Id ndm biin mdu (%) b mdt sau ciia mdu vdn ddn trong qud trinh 6 thdng phoi ngodi tidi Loai mdu
Mau khdng son be mdt
Mau son b l mdt mdu
tidng Mau phu b l
mat vecny mau vang
Nong dg MF Ddi chimg
MF 10%
MF15%
MF20%
Doi chung MF10%
MF15%
MF20%
Ddi chimg MF10%
MF 15%
MF 20%
Tiiang 1 5,77 0,27 0,40 0,53 2,30 0,57 0,23 0,73 1,47 1.17 0,80 1,00
n i d n g 2 38,70
10,40 8,90 8,63 31,40
7,30 5,30 3,70 32,90
6,70 6,37 3,87
Thdng3 43,47 13,27 10.63 9,73 40,43
12,17 9,47 8.53 39,27
10,63 8,77 6,43
Thdng 4 48,23 14,77 13,27 12.20 43,37 13,30 11,13 11,97 41,50 12,23 11,07 10,33
Thdng 5 55,37 23,20 20,80 17,80 47,50 20,23 16,90 15,50 46,50 22,00 18,33 16,23
Thdng 6 71,03 29,53 26,07 23,47 58,50 27,77 24,77 23,60 55,63 25.13 20,70 18,50 Theo cdc sd hdu thu duge sau 6 thdng cho thay:
van ddn ddi chirng cd ty Id nam biin mdu Idn hon hdn cdc mau van dan biin tinh vdi MF b cdc cdp nong do 10, 15, 20%. Ty Id nam biin mdu giam dan khi nong do MF tdng Idn.
Vdn khdng son phu bl mdt cd ty Id nam biin mdu cao hon so vdi vdn cd son phii bl mdt mdu tidng hodc vecny mdu vdng. Ty Id nam gay biin mdu cho van tdng theo thdi gian vdn dl ngodi trdi.
Nhiiu cdng tiinh nghidn cuu tidn till gidi da chung td gd biin tinh vdi mdlamin fomanddhyt cd kha ndng khdng cdc loai nam rat tdt. Hai tiong sd cdc CO chi khdng nam ciia go biin tinh vdi mdlamin fomandehyt la do am ciia go biin tinh thap, khdng du diiu kien cho nam phdt triin vd mdlamin fomanddhyt tich tu tiong vdch tl bdo, rudt tl bdo ngdn chdn sir phat triin cua cdc sgi nam (Lukowsky et al., 1999;
Rapp and Peek, 1996).
3. Mue dd nut b l m$t
Ty Id nut bl mdt phia trude cua van nhiiu hon hdn bl m$t phia sau do b l mdt phia truoc tiip xiic trvrc tiip vdi dnh sdng m$t trdi, bj anh hudng ciia qud tiinh quang hda, phd hiiy thdnh phan lignin ciia lop go phia tidn, khi gdp tidi mua, ldp Imhui phd hiiy niy bj xdi mdn, thiic day qua trinh nut, tach cua ldp v^
bl mdt phia trude.
Tuy nhidn, hidn tugng nirt bl mdt vdn xay ra chu yiu do sir thay doi do am trong van, ddc bidt ciia lop vdn ngodi cimg. Trong qud trinh dl mdu vdn dan ngodi tidi, vdn trai qua cdc chu ki hiit dm, nha dm, gdy ndn hidn tugng co nit, ddn nd, tao ra ndi ung su^t cho timg ldp van, khi ndi ung suat nay vugt qua gioi han bin klo ngang cua van, van se bi nut Hon th^
nira doi vdi vdn ddn, san pham dugc tao thanh tir cac ldp vdn mdng bdc, trong qud trinh bdc, tao ndn cac vit nut tl vi trdn b l mdt vdn; cdc chu ki hiit am, nha dm tiong van se ldm tdng ehilu sdu vd do rdng ciia cdc vit nut tl vi ndy.
KHOA HQC C 6 N G N G H I
Kit qua ddnh gid mire do nut bl mdt ciia vdn dan sau 6 thdng dl mau ngoai trdi dugc till hidn tidn bang 3.
Bang 3. Ddnh gid muc dd nut b l mdt trude aia cdc mdu vdn sau 6 thdng dl ngodi brdi
(tl Nong doMF
Doi chung MF10%
MF15%
MF20%
leo tidu chuan ISO 46284, (2003) Mau khong
son bd mat 3 2 2 2
Mau son mau trdng
2 1 1 1
Mdu phu vecny mau vang
2 1 1 1
Ghi chii: 0: khdng nut; 1: nut rat it; 2: nut it; 3:
mit trung binh; 4: nut nhidu; 5: nut rit nhieu.
Mdu dl tidn gid d ngodi tidi, sau 6 thdng, cho thay tidn bl mdt ciia mdu ddi chumg xuat hidn nhiiu vet mit hon cdc mau bidn tinh vdi MF d cdc cap ndng do 10%, 15%, 20%. Diiu ndy duge giai thich do: cdc
nut tl vj tidn bl mdt vdn dd lam giam do am cua mau, lam giam ty Id co nit dan nd, do dd lam giam tan sd vdt nut vd chilu sdu vit nut tien bl mdt van bidn tinh so vdi van ddi chung sau qua tiinh dl ngoai trdi.
Thay ddi ciia ndng do MF khdng dnh hudng nhiiu din muc do nirt tien bl mdt cua vdn ddn biin tinh.
Cdc mau van khdng son phu bl mdt cd ty Id nirt bl mat Idn hon ban cac mdu dugc son phii bl mdt mdu tidng hodc vecny mau vdng, do cac ldp son phii dd tao ndn ldp rao can bao vd bl mdt gd khdi sir phd buy ciia anh sang mat tidi vd ban ehl mdt phan thay ddi do am trong gd.
4. Muc do bong tdch, biin d ^ g
Van dan dd bi anh hudng bdi thay ddi do am cua mdi trudng hon gd nguydn do mdi lidn kdt bang keo dan giua cdc ldp vdn mdng cd chilu thd khac nhau.
Ty Id CO nit khde nhau giua cdc ldp van mdng tao ndn ngi ling suat cho mdng keo, tdi mdt gidi ban nhat dinh, mdng keo bi bong tdch, khi dd san pham vdn dan bj biin dang vd phd buy.
phan tir MF tich tu trong cdu tnic gd vd tiong cdc vit
Bang 4. Ddnh gid s6 lugng mdu vdn ddn cd hidn tugng bong tdch d canh vdn/tdng sd 3 mdu vdn/muc thi nghidm (ki hidu * la cd hidn tugng bien dang cua mau van)
Loai mdu Mau khdng son b l mdt
Mdu son b l mat mdu trdng
Mdu phii b l mdt vecny mdu vdng
Thdi gian DC MF10%
MF15%
MF20%
DC MF10%
MF15%
MF20%
DC MF10%
MF15%
MF20%
Thang 1 0 0 0 0 0 0 0 0 0 0 0 0
Thang2 0 0 0 0 0 0 0 0 0 0 0 0
Thang 3 0*
0 0 0 0 0 0 0 0 0 0 0
Thang4 1*
0 0 0 0 0 0 0 1 0 0 0
Thang 5 1*
0 0 0 1*
0 0 0 1*
0 0 0
Thang6 2*
0 0 1 1*
0 0 1 1*
0 0 0 Quan sat mau hang thdng cho thay: Hidn tugng
bong tdch tien canh ciia mau van chi xay ra d cdc mau ddi chiing sau tiiang thir 4, 5 vd 6. Cdc mau vdn dan biin tinh vdi MF cr cap nong do 10%, 15% hodn toan khdng xay ra hidn tugng bong tdch tiong 6 thang dl ngodi trdi. O nong do 20% cd xuat hien hidn tirgng bong tach van d mdu son mdu trdng vd khdng son bl mat vdo tiidng thu 6. Bong tach canh vdn d ty Id MF 20% cd till duge giai thich do nong do MF cao, tao ndn ldp mdng keo MF trdn bl mat van mdng, ldm giam tinh tham udt ciia bl mat, do dd lam giam chat lugng dan dinh cua mang keo.
Bidn dang cua mau van chu yiu Id mau vdn bj cong hinh cung. Vdi mdu van ddi chung, hidn tugng biin dang xuat hien tir thang thu 3 cho mau khdng son bl mat vd tir thdng thu 5 cho mau son phu bl mdt. Trong khoang thdi gian dl ngodi tidi 6 thdng, mau van biin tinh d cdc cap ndng dd MF khde nhau, kl ca loai cd son phii bl mdt vd khdng son phii bl mdt diu khdng bj bien dang, cong vdnh. Diiu ndy duge giai thich do tinh dn djnh kich thudc vd hidu qua lam giam do am mau ciia biin tinh vdi MF dem lai cho san phdm van dan.
NONG NGHIEP VA PHAT TRIEN NONG THON - KY 1 - THANG 10/2011
95KHOA HQC CdNG NGHt
5. Sir thay ddi mdu sdc ciia gd
Sir tiiay doi mdu sdc cua vdn duge ddnh gid b bl mdt phia tiude, phia tiip xuc tryc tiip vdi dnh sdng mdt tidi. Khi go/san phdin tir gb di ra ngodi mdi tiirdng tir nhidn, tiidnh phdn linhin Id tiidnh phdn hda hgc chu yiu nhdt cua go bj phd hiiy bdi dnh sdng mdt tidi (tia UV. tia sdng nhin thdy dugc...). Vi linhin cd mau ndu ndn khi ldp linhin phd buy bj rira tidi, go trd ndn b^ic mau. Tuy nhidn, bl mdt gd/vdn cung nhanh chdng bj xam chilm bdi cdc loai ndm bidn mdu. Do dd mdu sdc cua gd/vdn ldp bl mdt bj thay doi. Dl danh gid su thay ddi mdu cua van ldp bl mdt, dd
diing tiiang do CIE L, a, b. Vi tiidi gian phoi mdu c6 h^n (6 tiidng), cdc gid ti-j a (chi sd do dd mdu tir xanh Id cdy sang dd), b (chi s6 do dd mdu tir xanh lam sang vdng) ciia mdu vdn it thay dii, ndn ti-ong nghidn ciru ndy chi xdc djnh sir tiiay dii cua gid ti-j L* (chi sd do dd mdu tir tidng sang den; 0-100). Dl ddnh gid su thay dii dd sdng ciia mdu so vdi ban ddu, dd diing djii lugng delta L*
Kit qud sir thay doi ciia gid trj L* vd delta L*
tiong 6 thdng dl mdu vdn ddn ngodi trdi nhu sau:
Mdu khdng son phii b l mdt
ihung I Ihung2 thung3 Ihfing4 t h a n g )
—•—4fc\i chung - » - 10% A l$% — • — 2 0 H Ihang6
Hmh 3. Su tiiay doi ciia chi sd L* vd delta L* b m$t trude ciia mdu khdng son phii b l mdt trong 6 thdng dl ngodi trdi
Trong trudng hgp mau khdng son phu b l mdt, ehl so dd sang L* cua ca mau vdn doi chung vd mau van biin tinh giam di nhanh chdng, nhat la trong 3 thdng dau. Gid tri delta L* chi sir thay doi ciia chi sd do sang L* cua mau vdn doi chung cao hon ciia mau vdn biin tinh. Khi nong do MF tdng Idn tir 10%, 15%
din 20% thi delta L* giam dan, tuy khdng cd su khde nhau rd rdt giira nong dg MF 15% vd 20%. Nhu vdy
vdn ddn biin tinh vdi MF cd tac dung lam tdng dp on djnh mdu cho mdu van. Mdu ciia cac mdu van bj sam di chu yiu la do ndm biin mdu xdm nhdp Idn bl m$t van, ddc bidt qua cac vet mit Vdn doi chung bj nin xdm h ^ nhiiu nhat ndn mau bj tdi di nhat, vi vdy delta L* thay doi nhiiu nhdt
lAhs. son b l m^t mdu tdbg
n i l d a u thanRl thanH2
• dAi chirng — • lhanH3 - 10%
lhanH4 15% -
thanu^
• — 2(1%
t h a n g 6 thang 1 t h a n g 2 thang 3
— d6i chirng — • — 10%
t h a n g 4 15%
t h a n g 3
- 2 0 %
m
Hinh 4. Sir thay doi ciia ehi s i L* vd delta L* b mdt trude ciia m&u son phii b l mdt mdu trdng trong 6 thdng d^
ngodi trdi
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Mdu phii bl mdt vecny mdu vdng
Hinh 5. Sir thay doi ciia chi sd L* vd delta L* b mdt trude ciia mdu phii bl mdt vecny mdu vdng tiong 6 tiidng dl ngodi trdi
Chi sd L* vd delta L* cua mau vdn dan biin tinh dugc son phii khdng thay ddi nhiiu trong sudt qud trinh dl mau d ngodi trdi, do bl mdt vdn rat it bj nut ndn cdc loai nam biin mdu khd xdm nhdp dugc vdo bdn tiong vdn qua ldp son phu. Nguge lai, vdi vdn ddi chimg, chi sd L* vd delta L* thay ddi rd rdt tiong qud tiinh phoi mdu do bl mdt van bj nirt nhiiu hon vdn bien tinh, cdc loai nam biin mdu xdm nhdp vdo bl mat bdn tiong ciia vdn xuydn qua ldp son mdu tidng hoac phii vecny mdu vdng. Vi vdy, mdu sdc ciia van dan biin tinh it thay ddi hon vdn dan ddi chiing.
Ndng do ciia hda chat bien tinh anh hudng khdng ro ret din muc do thay ddi mdu sdc cua van dugc son phu bl mat.
IV. KET LUAN
Vdn mdng gd bd dl duge ngam tam d diiu kidn thudng tiong dung djch MF d cdc cap ndng do 10%, 15%, 20%, sau dd qud trinh da tu cua nhua MF dugc ket hgp ciing vdi qua trmh dp nhidt de san xuat van dan bidn tinh. Trong qud trinh phoi mau van ngodi tidi, cdc tinh chat cua van ddn biin tinh duge cdi thidn rd ret so vdi vdn ddn doi chiing. Khi nong dg MF tang Idn tir 10% din 20%, do am vd bidn do tiiay ddi do am cua van ddn biin tinh giam, ty Id nam bidn mau d mdt sau cua vdn cung giam, do on dinh mdu sac d mat trude cua mau vdn khdng son phu bl mdt tang Idn, tuy nhidn, do dn djnh mdu sdc d mdt trude ciia mdu van cd son phii bl mdt thay ddi khdng nhiiu. Thay ddi cua nong do MF khdng anh hudng dang kl den muc dd nut bl mdt cua cdc mdu vdn bien tinh, mac dii van dan biin tinh cd muc do nirt bl mdt tiiap hon hdn so vdi van dan doi chiing. Nong do MF 20% khdng dem lai hieu qua chong bong tach canh van tit hon so vdi nong do MF 10% vd 15%. Do
<J6, ngdm tam vdn mdng d nong dd MF tir 10-15% la dam bao tot kha nang chdng chiu cdc yiu to cua mdi
trudng ngodi tidi cho van dan biin tinh. Van duge son phu bl mdt cd kha chdng chiu mdi tiudng ngodi tidi tdt hon cdc mau vdn khdng son phu bl mdt.
TAI L P THAM KHAO
1. Deka M. and Saikia C. N. (2000). Chemical modification of wood with thermosetting resin: effect on dimensional stability and strength property.
Bioresource Technology, 73(2): 179-181.
2. EN 927-3 (2006). Paints and varnishes Coating materials and coating systems for exterior wood - Part 3: Natural weathering test.
3. Inoue M., Ogata S., Nishikawa M., Otsuka Y., Kawai S. and Norimoto M. (1993). Dimensional stability, mechanical-properties, and color changes of a low-molecular-weight milamin fomandihyt resin impregnated wood. Mokuzai Gakkaishi, 39(2): 181-189.
4. ISO 46284 (2003). Pamts and varnishes Evaluation of degradation of coatings Designation of quantity and size of defects, and of intensity of uniform changes in appearance - Part 4: Assessment of degree of cracking.
5. Kloser L, Trinh H. M., Hauptmarm M., MiUtz H. and Mai C. (2009^. Chemical modiffcation of
veneers to produce plywood for outdoor application.
In: Proceedings of the 4th International Symposium on Veneers Processing and Products, Espoo, Finland.
6. Lukowsky D. (1999). Holzschutz mit Melaminharzen. PhD Thesis, University of Hamburg, Germany.
7. Rapp A. 0. and Peek R. D. (1996). Melamine resins as preservatives - Results of biological testing.
NONG NGHIEP VA PHAT TRIEN NONG THON - KY 1 - THANG 10/2011
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Proceedings of the International Research Croup on 9. Trjnh Hiin Mai (2009) Veneer modification Wood Preservation. Document No: IRG/WP 96- for the production of exterior plywood. Ph.D Thesis, 40061. University of Goettingen, Germany.
8. Rapp A. 0 . Bestgen H., Adam W. and Peek R. 10. Williams R. S. (2005). Weathering of D. (1999). Electi-onenergylossspcctivscopy (EELS) wood. In: R. M. Rowell (Editor), Handbook of for quantification of cell-wall penetration of a wood chemistry and wood composites. CRC milamin resin Holzforschung, 53(2): 111-117. Press. 139-211.
RESEARCH TO IMPROVE THE NATURAL WEATHERING USABILriT OF PLYWOOD BY MELAMINE FORMALDEHYDE MODIFICATION
Trinh Hien Mai Summary
There have been many studies on wood modification with melamine formaldehyde in the world; however, the modification of wood veneer by melamine fonnaldehyde has been newly and never been studied in Vietnam. To enhance the quality of plywood when used outdoor, in this study, the veneers were impregnated in the melamine formaldehyde solutions at the concentraUons of 10%, 15%, and 20%; and then, the modified plywood was produced as usual. The condensation (curing) of melamine formaldehyde resin was combined with die hotpress process. The results revealed that the melamine fonnaldehyde modified plywood was less affected by natural weathering factors than the control plywood, such as: reduced moisture content and reduced fluctuation of moisture content between wet and dry periods, decreased proportion of blue stain on the reverse sides, enhanced color stability, reduced cracking on the front sides, decreased delamination and deformation of the plywood panels. The melamine formaldehyde concentration from 10-15% is reasonable to produce modified plywood for natural weathering use. The coated plywood showed better outside properties than the uncoated plywood.
Keywords: Blue stain, cracking, delamination, deformation, melamine formaldehyde, modided plywood, natural weathering factors.
Ngudi phan bidn: GS.TS. Hd Chu Chir
