Nghiên cứu tính ổn định kích thước của gỗ trám trắng xử lý bởi DMDHEU

KHOA HOC CbNG NGHE

MGHIEIV Ciiu TilMH DIM DflMH KICH THIJOC CUA

GA TRAIVI TRAIMG X U LY BOI OMDHEU

T? Thj Phuong Hoa^

T6MTAT

Nghifen ctiu tinh dn dinh kich thudc ctia gd tram frdng xir ly bdi DMDHEU (dimetila dihydroxyt etylen

urea) nong d6 khac nhau: 10%. 20%, 30%, 35%, 40% frong hai trudng hpp gd c6 qua xti ly lupc d nhi^t dd 70°C

va khong xu ly lupc trudc khi tdm hoa chdt Khi xtr ly hoa chat vdi cac nong dp nhu frfen vdi 5.5% chat xtic

tac MgClz da lam tang tinh on djnh kich thudc ctia gd tram frang; dp tang khdi lupng dat tir 9,85% din

26.24%. chiing to hoa chat da tham vao gd. Khi nong do tang tir 10%-35% lirong boa chat vao gd s€ tang, tuy

nhifen sau do se hau nhu khong tang nua, frong khoang tir 35-40%. Khdi lupng thi tich kho kifit ctia mlu

trudc xu ly va mdu ddi chting la 0,537 g/cm', con ctia mau xii ly dat tir 0.569 den 0.637 g/cm', tang tir 5,96%

din 19,85% so vdi trudc xti ly. Cac chi tifeu vl dn dinh kich thirdc: dp tang khdi lupng (dac trung cho lupng

hoa chat vao go), dp tang khdi lupng thi tich ctia mau gd co xir ly lupc cao hon so voi mlu gd khong xOt ly

lupc trudc khi tdm hoa chat D6 am gd ctia mdu ddi chting ldn hon eda mau xti ly khi lim giir frong cimg

diiu ki$n moi trudng. 6 diiu ki6n moi truong vdi nhi?t dp (20t2)"C va dp am (65±3)% dp dm cua mau ddi

chting la 12.37%, trong khi do do am ctia mau xtr ly dat 9.68% din 8,40%. Ty 1$ dan nd ldn nhdt theo chiiu

tiep tuyen ctia mdu ddi chting la 6,81%, con chi ti6u nay cua mlu xir ly la 4,11% din 2,89%, tuong ting vdi h^

sd ASE dat 39,63% din 57,54 %. H? sd chdng dan nd ctia mlu khong qua xii ly lupc va qua xir ly lupc trudc

khi xii ly hoa chat khong ch6nh l$ch nhilu khi so sanh d cimg dp tang khdi lupng.

Tir khda: Tram tiing, ti'nh on dinh kich thudc, DMDHEU.

I. DAT VAN D^

Chat lupng gd dupe xdc dinh bdi nhilu ddc tinh

Uln quan din kha ndng su dung gd vd dupe ddnh gid

bdi mtic dp phii hpp vdi timg muc dich str dting cu

thi, mpt sd ddc tinh chii yeu ddc trung cho chat

lupng gd cd thi k l din la tinh dn djnh kich thudc, dp

bin sinh hpc, dp bin co hpc, kha ndng chdng chiu tia

tii ngoai (tia UV), kha ndng chdng chju tdc ddng ctia

mdi tiirdng frong diiu kiln hi nhiln (bao gdm tdc

dpng ciia dm, mua, ndng, sinh vat) [4,5].

Thdnh phdn hda hpc chinh ciia gd gdm

xenluloza, himixenluloza, linlin, frong phdn tiir ciia ca

ba tiianh phdn ndy diu chiia nhdm hydroxyl nin gd

cd kha ndng htit nha dm manh. Mdt khdc, gd cd cdu

tao mao dan, trong gd cd cdc mao dan ldn (rupt t l

bao vd khe hd giua cdc t l bdo) vd cdc vi mao dan

trong vdch tl bdo. Nudc ttr do tdn tai frong cdc mao

dan ldn vd sir thay ddi lupng nudc nay khdng lam

tiiay ddi kich tiiudc gd. Nude thdm ndm frong vdch tl

bdo vd loai nudc ndy anh hudng din mpi tinh chat gd,

kich tiiudc gd tiiay ddi khi lirpng nudc ndy thay ddi.

Ndi tdm lai, khi dp am mdi trudng tiiay ddi dp dm gd

tiiay ddi vd ddn di n tiiay ddi kich tiiudc go. Tinh dn

djnh kich tiiudc cua gd la chi tilu vat ly quan frpng

dl ddnh gid chat lupng vd kha ndng sir dung gd. Do

Trudng D^ii hpc Lam nghifp

vgy mdt frong nhiing bi|n phdp ndng cao tinh dn

djnh kich thudc ciia gd Id biin tinh hod hpc gd bdi

mdt sd loai hod chdt khi phdn iing vdi gd sfi tao ra

liln kit ngang giua cdc nhdm OH vd nhdm chtic ciia

hod chat xti ly, ddng thdi cd thi tao ra mdng polyme

d frong gd [4]. Trong nhirng ndm gdn ddy hod chat

DMDHEU - mdt loai hod chdt ciia ngdnh dlt may dd

dupc nhilu nudc nghiln ctiu thdnh cdng frong vile

ndng cao tinh dn djnh kich thudc vd nhilu chi tilu

chdt lupng gd nhu dp bin sinh hpc, kha ndng chdng

chju tdc ddng ciia mdi tnrdng frong diiu ki|n tti

nhiln [4,5]. Khi DMDHEU dupe tam vdo gd dudi tdc

ddng cua chat xtic tdc vd nhi|t dp, mdt phdn hda chdt

tham gia phdn ling vdi thdnh phan hda hpc ciia gd

tao liln kit ngang, ddng thdi xdy ra phdn iing triing

ngung (polime hda) ldm cho vdch tl bdo gd truong

nd va thi tich cua gd dat din miic ldn nhdt Kit qud

la tao ra mang polime vd ldm cho gd khdng cd khd

ndng quay frd lai kich thirdc ban ddu. Do dd tinh chdt

ciia gd dupc cdi thiin.

DMDHEU cd khd ndng phdn iing vdi 2 nhdm

hydroxyl gdn k l oxy vdi liln kit ddi. Trong phan irng

chinh, cac nhdm hydroxyl nay phan img vdi cdc

nhdm hydroxyl khdc vd tao nin cdc hln kit ete vd

nude thodt ra (Krause va ddng tdc gid, 2003). 6 ddy,

hda chdt tao liln kit ngang vdi xenlulo cd thi xay ra

vdi nhdm N-metiiylol vd vdi nhdm hydroxyt d vj tri 4

NONG NGHIEP VA PHAT TRIEN NONG TH6N - KY 1 THANG 9/2011 91