TAP CHi HOA HOC T. 52(1)101-106 THANG 2 NAM 2014
NGHIEN c u u TINH CHAT CO LY VA CAU TRUC CUA VAT LIEU COMPOZIT NHUA N^N POLYPROPYLEN VA HAT GYPSUM
BieN TI'NH NATRI DODECYL SUNPHAT
Nguyen Vu Giang'*, Do Quang Trung^, Tran Hiru Trung', Mai Dire Huynh', Nguyen Quang Minh' ' Viin Ky thudt nhiit ddi, Vien Hdn ldm Khoa hpc vd Cdng nghi Viit Nam
^Khoa Hda hpc, Trudng Dgi hpc Khoa hpc fu nhiin. Dgi hoc Qudc gia Hd Ndi
^Khoa Khoa hpc tu nhiin, Trudng Dgi hpe Hdi Phdng Din Tda soan 14-10-2013
Abstract
In this study, the composite materials based on polypropylene (PP) and waste gypsum (Gyp) was prepared by melt mixmg method in a Haake mixer (Germany). Original Gyp (OGyp) was modified by surfactant as sodium dodecyl sulfate (SDS) (abbreviated as MGyp). Analysis of Fourrier transform infrared specttoscopy (FT-IR) demonsttated that the SDS was grafted onto the surface of Gyp particles Besides, the results of thennogravimetric analysis (TGA) revealed the decorr^josition peak of SDS at the temperature around 580-660 "C. Melt Theological properties of con^osite materials showed the increase in the relative viscosity of the modified Gyp composite. In other hand, investigatation of mechanical properties of composites also showed that the MGyp increased the tensile sttength and Young's modulus of PP/MGyp up to 8.23 % and 43.78 % in comparison with the pure PP, respectively. Field emission scanning electron microscopy (FESEM) images desmonttated the dispersibility of MGyp on PP matnx was better than thatoftheOgyp.
Keywords: Gypsum, polypropylene, sodium dodecyl sunfate, polymer composite, mechanical properties.
1. MODAU
Vat li?u polyme compozit vdi pha phan tin sir dyng cac hat vd ca ddng vai trd chat ddn hoic chat gia cudng ca tinh da nhgn dugc sy quan tam nghien ciiu cua nhilu nha khoa hgc trong nudc va qudc te vi chiing CO the cii thi|n dang kl cic tinh chit ca ly.
nhiet, va giam gii thanh sin xuit. Cic vat lieu vd ca pho biin la CaCOj. bdt talc, hot than den, hgt clay, bentonit.... Tuy nhien gii ban ciia nhimg nguyen lipu nay khi cao [1-3]. Hgt gypsum (Gyp) la sin pham phy ciia qua frinh sin xuat axit photphonc. Cic axit photphoric thu dugc bing cich hda tan qugng phosphate trong dung djch axit sunfuric. Cdng ty DAP Vinachem Viet Nam da chl tao cac axit photphoric theo each niy dl sin xuit phan bdn cd chira photphat. Lugng khi ldn hgt Gyp thu dugc yong qui hinh san xuit nay dugc luu giu frong cic bii thai chilm dien tich ldn. Vi viy, viec su dung hat Gyp phi thii chl tao vgt lipu polyme compozit khdng chi gdp phin giii quyet vin de d nhiem mdi trudng ma cdn la mgt giii phip khoa hpc hChi ich, cai thi^n dp ben ciia vgt H$u compozit.
Tuy nhien, do be mat hgt Gyp (CaS04.2H20) ed khi nSng hip thu nudc cao din tdi sy tuong tic mgnh giira cac hgt, dieu nay dan den sy tgp hgp ciia cac hgt trong qua trinh che tao vgt lipu compozit, kit tu, dim va trd thinh khuyit tit trong cau tnic compozit. Do dd, be mat hat Gyp ban diu (OGyp) cin dugc bien tinh de giim tinh ua nudc, ting tinh ky nude, nhd dd lim tang kha nan§ tuang hgp va kit dinh cua hgt va nhya nen. Mpt sd nghien ciru bien tinh hgt Gyp bdi axit stearic vi su dung de che tao vit lieu compozit polyvinyl clorit/Gyp da dugc cdng bi [4,' 5].
Nghien cuu tdng hgp hgt CaS04 biin tinh bdi natri dodecyl sunphat (SDS) tir canxi hydro photphat vi img dung de chl tao compozit polyetyIen/CaS04 biin tinh da dugc cdng bd [6]. Ket qui nghien cim cho thiy dp bin keo diit va dp ben lao hda nhi?t ciia compozit tang ding ke so vdi compozit su dyng hgt CaS04 khdng biin tinh. Tuy nhien, viec tdng hgp hgt CaS04 biin tinh yyc tiip SDS khdng tan dyng dugc ngudn nguyen lipu hgt Gyp phi thai. Trong nghieti cdu niy, chiing tdi tien hinh bien tinh hgt Gyp phe thii bing SDS sCr dyng phuang phip trpn vgt ly kit hgp nang lugng nhi?t. SDS la mpt hgp chat him co
TCHH, T. 52(1), 2014
vdi cdng thiic CH3(CH 2)iiOS03Na, la mgt anion hogt dgng bl mat. Nhdm anion sunfat cd kha ning tuang tic vdi be mat ciia hat Gyp phi thii nhd sy thay the nudc dugc giai phdng bdi tac nhin nhiet.
Nhya isotactic polypropylen (PP) ddng vai trd pha lien tuc trong nghien ciiu nay. Thanh phin y i cau tnic cua miu hgt Gyp bien tinh vi khdng bien tinh duge phan tich bing phd hdng ngoai FT-IR v i TGA.
Khao sat cac tinh chit ca ly vi die tinh luu biin ndng chiy so sinh cic mau compozit sii dung hat Gyp cd va khdng biin tinh. Hinh thai ciu tnic cua compozit dugc dinh gia sii dung ky thuat chyp anh be mat phi buy mau bang Idnh hien vi dien hi quet trudng phit xg (FESEM).
2. THUC NGHIEM VA CAC PHU'ONG P H A P NGHIEN CUTJ
2.L Ngnyen lieu
Hat gypsum (Gyp) phe thii dugc cung cap bdi Cdng ty Cdng ty DAP Vinachem Viet Nam, Hii Phdng. Natri dodexyl sunfat (SDS) la sin phim thuang mgi ciia Cdng ty Merck, do tinh khiet 98 %.
Nhya isotactic polypropylen (PP) dugc sin xuat d dgng hat ciia Cdng ty LG (Hin Qudc) cd ty trpng d = 0,96 g/cm', chi sd chay MFI = 2,5 g/IO phut/2,16 kg/
190 °C.
2.2. Thyc nghiem 2.2 1. Biin tinh hgt Gyp
Gyp dugc biin tinh SDS theo phuang phap trdn ndng chiy nhu sau: ban diu, hgt Gypsum (OGyp) dugc siy khd, nghien mjn va ray sang cd mat ludi 0,125 mm. Tiep theo, hdn hgp Gyp va SDS (chilm ty le 4 %kl hgt Gyp) dugc trgn diu vdi nhau vi siy d nhi?t dg 205 "C [6] hrong 120 phiit. Tiip theo, hdn hgp dugc lim ngudi, Ipc va rua sach nhieu lan bing dung dich cdn:nudc = 1:1. sau do siy khd d nhiet dp 80 "C din khdi lugng khdng ddi thu dugc hgt Gyp biin tinh (MGyp).
2.2.2. Che tao vdt Ueu compozit PP/Gyp
Vgt lieu compozit PP/Gyp dugc chl tgo theo phuang phap ndng chiy fren thiit bi tr^n ngi Haake Rheomix 610 (CHLBD) vdi dilu Iden chl tgo nhu sau; nhi$t do phoi trdn 180 "C, tdc do true quay 60 vdng/phut, thdi gian phdi trgn 5 phiit. Sau dd, cac miu dugc ep dinh hinh tgo miu tren may ep ndng Toyoseky (Nhat Bin) d nhiet dg 190 "C, ap suit ep 5 MPa. Tiep theo mlu dugc lam ngudi xudng nhipt do
Nguyen Vu Giang vd cpng syr phdng v i d l dn dinh trong 24 gid trudc khi sir dung.
Ham lugng MGyp va OGyp dugc can theo ti 1? khoi lugng la 5,10, 15,20 va 25 %kl compozit.
2.3. Cac phirong phap nghien cihi
Tinh chit luu biin trang thai ndng chay ciia vat lieu compozit dugc do tren thiet bj trpn Haake (CHLBD) cd su dung phin mim Polylab. Cac tinh chit ca ly dugc xie dinh tren thiet bj do da nang Zwich Tensiler 2.5 (Due) vdi tdc do keo 50 mm/phut, theo tieu chuin ciia ASTM D 638. Pho hong ngoai biln ddi chudi Fourier (FT-IR) diryc thyc hien tren thiet bj Nexus 670 (My) vdi dp phan giii l i 8 cm"', sd lin quet l i 16 trong khoang budc sdng tir 400 cm"' din 4000 cm"', su dyng phuang phap do ep vien KBr. Miu dugc do tren may Shimadzu TGA 50H, tdc dp ddt 10 °C/phiit hong mdi trudng khi Argon tir nhiet do phdng den 800 "C.
Hinh thii hgc be mat ciia vit lieu compozit dupc thyc hien tren thiit bj hien vi quet trudng phat xa (FESEM) S-4800 cua hang Hitachi, Nhat Ban, tai Vien V | sinh Dich t l Trung uang.
3. KET QUA VA THAO LUAN
3.1. Nghien cuu phd FT-IR ciia mau Gyp biln tinh (MGyp)
Phd FT-IR ciia cic mau OGyp vi MGyp trinh bay tren hinh 1. Sd sdng 1133 cm"' die trung cho dao dgng ctia nhdm S04^" nam trong mat phing, Dao dgng tgi budc sdng 600 v i 670 cm"' tuang ung dao dgng ngoai mat phing ciia nhdm S04^'. Viing pic rdng xung quanh sd sdng 3400 cm"' die frung cho dao dgng nhdm -OH ciia nudc im [7]. Ngoai ra, xuat hien cic pic tai 3486 va 3529 cm"' die tnmg cho nhdm -OH trong nudc lien kit vdi Gyp. Pho FT-IR eua MGyp, ngoii cic pic dac trung cua nhdm SO4 cdn xuat hien cac nhdm pic mdi nhu 2919 cm"' va 2862 cm"' ia dao dgng ddi xiitig va bat ddi xiing ciia nhdm -CH2-, ngoai ra pic 1383 cm"' la dao dpng ci\
keo cua nhdm -CH2- hoic dao dgng bien dgng ciia nhdm -CH3 tat c i cic dao dgng tren die trung cho phin khdng phin eye ciia SDS tr8n hat Gyp, dieu niy chi ra sy ton tgi mach hidro cacbon ciia SDS tren hat Gyp. Kit qua phan tich pho FT-K. cho thSy cic phan tir SDS d^ tuang tic va kit dinh tot tren be mat ciia MGyp.
3.2. Phan tich nhiet cua mau OGyp & MGyp Gian dd TGA ciia cac miu gypsum bien tinh 4
%kl SDS (MGyp) v i mlu gypsum chua bien tinli (OGyp) dugc gia nhipt din 800 °C trong mdi trucmg
TCHH, T. 52(1), 2014
Arjgon dugc trinh bay tren hinh 2. Tii hinh 2 cd thi thay, sy giim khdi lugng mgnh cua cae miu xiy ra chii yiu trong khoing nhipt do 60-150 "C. Ban diu, sy mit khdi lugng ciia mau xay ra do sy bay hai cua nudc ty do cd trong miu, qua trinh niy diln ra trong khoing 60 din 100 "C. Trong khoing tur 100 "C din khoing 150 °C, qui trinh mit khdi lugng do sy tach nudc trong tinh the xay ra theo qua trinh sau [8, 9]:
CaS04.2H20 ->• CaS04.1/2H20 -^ CaS04
Hinh 1: Phd FTIR cua cac miu Ogyp va Mgyp
Hinh 2: TGA cua cac miu Ogyp vi Mgyp
Sy chenh lech mat khdi lugng cua cic miu OGyp va MGyp trong giai dogn niy li do qua trinh bien tinh trong khoang nhiet dp 205 "C ciia mau MGyp [6] (nhiet dp ndng chiy ciia SDS) da lam mit nudc tinh thi trong miu. Tuy nhien sau bien tinh, qua hinh tii hiit am ciia miu da xay ra, dilu nay giii thich sy mat khdi lugng cua miu MGyp nhd ban va xiy ra sdm han so vdi miu OGyp. Sau qua trinh tach nudc, sy mit khdi lugng tiep tuc xay ra do sy phan buy cham ciia thanh phin khic trong gypsum.
Trong khoang nhi?t dp 150 din 800 °C, sy mit khdi lupng ciia cac miu MGyp vi OGyp lin lugt la 3,90
%kl va 3,15 %kl. Sy chenh l?ch nay do sy ddng gdp cua SDS cd trong mlu MGyp. Qui trinh phin hiiy
Nghien cdu tinh chat ca ly vd...
ciia SDS dugc quan sit xay ra trong khoing tir 580 den 660 °C [10], khdi lugng mit eua miu dugc tinh toin theo pie niy l i 0,73 %kl. Nhu vgy, hieu suit biln tinh ciia SDS len be mat Gyp l i khoang 19 %.
3.3. Nghien ciru tinh chat Imi bien trang thai nong chay cua vat lieu compozit PP/Gyp
Tinh chat luu bien trang thai ndng chay cua vat lieu compozit PP/Gyp dugc thyc hien fren thiet bj trdn ngi Haake thdng qua viec khao sat md men xoan cua hdn hgp ndng chay trong qua trinh phdi trgn. Giin dd md men xoan va momen xoin can bing cua nhya PP ban diu va vat lieu compozit PP/Gyp dugc frinh bay tren hinh 3(a) vi 3(b). Khi bat dau ngp lieu va ddng budng trpn, md men xoin tang len va dgt gia tri eye dai. Hien tugng ting Ien va dgt gia trj eye dgi cua md men xoin la do nguyen lieu ban diu deu d trgng thai rin. Vdi cac miu compozit, hdn hgp ndng chay cd dg nhdt cao lam tang ma sat trong budng trdn, do dd md men xoin cue dgi cua hdn hgp ting manh so vdi PP. Dac biet, vdi mau su dung MGyp, md men xoin eye dgi ting, chiing td cd su tuong tac giua PP va hat MGyp rd ret, dan den md men xoan ting cao. Sau dd, ba khoang nhiet va lye ma sat tryc vit eung cap nang lugng lam PP mem din va ndng chay, md men xoin dgt gia tri can bing khi PP ndng chay hoan toin sau 5 phiit.
Hinh 3 (b) md ta chi tilt mdi quan he giira md men xoin can bing ciia PP/OGyp va PP/MGyp vdi cac ham lugng khac nhau tir 5-25 %kl. Vdi miu PP/MGyp gii tri md men xoan cin bing cao han so vdi PP/OGyp. Vdi ham lugng chit phan tan thip (nhd han 15 %kl) cho ca hai loai, gia trj md men xoan can bang cho thay xu hudng ting dan so vdi PP ban dau la do tuong tac npi ma sat giira Gyp vi PP.
Tuy nhien, khi ting him lugng chat phan tan cao hem 15 %kl. gii trj momen xoan can bang ciia compozit cd xu hudng giam. Dilu nay cd thi dugc hieu khi him lugng chat ddn ldn, the tich hdn hgp giam. he sd diln diy trong budng trgn giim, din din chi can mdt gii tri md men xoin dii nhd de phoi trdn. Gii tri md men xoin ciia miu compozit sir dyng MGyp cao hon so vdi miu sii dung OGyp cd the Ii do tuang tac ciia SDS tren be mgt hgt Gyp vdi nhya nin PP. Dieu niy cii thien sy phan tin va tuang hgp ciia MGyp vdi nhya nin tot han so vdi hat OGyp.
TCHH.T. 52(1),2014 Nguyin VU Giang vd cdng stt
(a)
PPyQGyp SS/*
PPfMGyD 95^5
t fe^
VHam iifo-ng Gyp (%kl) TnoigiantrOn (phut)
Hinh 3: (a) Gian dd md men xoin va (b) md men xoin can bing ciia miu PP/Gyp
3.4. Do ben keo diit va do gian dai khi dirt ciia v^t lieu compozit
PP. Nhd do da cai thien dugc tinh chat ca ly so vdi nhya nen ban diu va vit lieu sir dyng OGyp. Nhung khi tiip tuc tang lugng MGyp vugt qua 15 %kl^ sir phin tin trd len khd khan hori, cic hgt MGyp de co cym va hinh thanh cac khuyit tgt hong ciu true, do dd lam suy giim mgnh do bin keo diit cua vit Heu compozit.
Bdng T. Kit qua do bin keo dut, dp gian dii khi diit ciia vat lieu PP/Gyp
Ham luong Gyp (%kl)
Hinh 4: Anh hudng ciia him lugng chat phin tan tdi dp bin keo diil cua cac mau compozit Hinh 4 trinh bay mdi tuang quan gjira dp ben keo dut cua compozit theo ham lugng chat phin tin.
Dp bin keo diit cua miu PP ban diu xac dinh dugc la 31,6 MPa. Doi vdi miu PP/OGyp, gia trj dd bin keo dirt ciia cic mau compozit giam dan khi tang him lugng OGyp so vdi miu PP ban dau. Trong khi dd, vdi ham Iugng MGyp 5 %kl h-ong compozit, gia tri do bin keo dirt cao ban so vdi mau PP ban dau va dat gia tri cao nhat la 34,2 MPa. Khi tiep tyc tang ham lugng MGyp, gia tri dp ben keo dut giim dan.
Tuy nhien sy suy giim niy l i chim hon dang ke so vdi miu compozit sir dyng OGyp. Vdi mau 20 %kl chit phan tan. dp ben keo diit dgt gia tri lan lupt la 28.3 vi 27,8 MPa tuang irng cac mau sir dung MGyp va OGyp. Nhu vgy. d ham lugng chit don thip, SDS the hipn ro vai trd cua chit bien tinh nhd kha nang khuech tan bdi goc hidrocacbon mach dii cua phan tu SDS bim tren hgt Gyp tuang tic vdi nen
Gyp, %kl 0 5 10 15 20 25
Do gian dai khi dot, % OGyp
618 32,8 25,1 19,1 18,3 15,34
jMGyp 618 25,6 19,1 13,5 12,9
9,9 ,^, Bang 1 md ta anh hudng ciia ham lugng chat phan tan tdi do gian dai khi ddt ciia cac mau compozit. Kit qua cho thay khi cd mat chat phan tan, do gian dai khi dut ciia compozit cd xu hudng giam, muc do giim phu thugc ham lugng hat Gyp c6 mgt. Cac miu compozit siif dyng MGyp cd toe dp glim nhanh ban so vdi mau su dyng OGyp. Miu PP ban diu cd do gian dai khi dirt dgt gia trj li 618 %- Khi ham lugng chat phin tan nhd. dg gian dai khi dut giam cham so vdi miu PP ban diu. Vi dy, d ham lugng 5 %kl cua Gyp dO giin dai ciia mau PP/OGyp dat gia tri la 32,8 %, trong khi do miu sir dyng MGyp la 25.6 %. Khi tang ham lugng_Gyp len tir 15-25 % do gian dai khi dirt cCia cac mlu niy gianj mgnh han. Tgi ham lugng 25 %kl Gyp do giin dai
TCHH.T. 52(1),2014
ciia mlu chua bi4n tinh la chi con li 15,34 %. trong khi d(S mlu sir dgng MGyp giam nhanh hem con 9,9 %.
3.5. Mo dun din hoi ciia v^t Ueu compozit
C Z H M G w
1 « f
,
Ham lirong Gyp (%W)
Hinh 5: Mo dun din hdi PP/OGyp va PP/Mgyp
Md dun dan hoi la dgi lugng die trung cho do cimg cua vit lipu (thdng sd quan trgng ddi vdi vgt ]i?u san xuit cac san pham kit ciu), dugc dinh nghia bing ty s6 giiJa iing suit keo chia cho biln dgng keo.
Tren hinh 5 phan anh sy phy thupc md dun dan hdi vao ham lugng Gyp. Mau PP ban diu cd md dun din h6i li 756 MPa. Khi phoi trpn PP vdi hgt Gyp, gii tri md dun din hdi cCia cic miu compozit tang dan va Idn han so vdi miu PP ban dau. Trong do, cic miu sir dyng MGyp cd gia tri md dun dan hdi cao han so vdi mau OGyp. d ham lugng ldn nhat 25% Gyp, gii
Nghien dm tinh chdt ca ly vd...
tri md dun dan hdi eua cic miu PP/OGyp va PP/MGyp dat gia tri lin lugt li 1061 MPa va 1083 MPa cac gia tri niy la ting gin 1,4 lin so vdi miu PP ban diu. Ket qui niy cho thiy, chit phan tin ddng vai trd Iam ting do eumg ddi vdi nin PP ban diu. Mat khac, viec su dung SDS biln tinh tuang tic tren hat Gyp tgo sy lien ket chit che vdi nin PP, gdp phan cii thien gii tri md dun dan hoi ciia vgt lieu.
3.6. Phan tich can true hinh thai hoc vat lieu PP/Gyp
Hinh 6(a) v i 6(b) phan inh ciu tnic hmh thai hgc bl mat phi hiiy mau su dyng I ^ thuat FESEM cua vit lieu compozit PP/Ogyp va PP/MGyp tuang ling. Quan sit tren hinh 6 (a) cho thiy, hgt OGyp kit tu vi tgo dam tren nen PP vdi kich thudc khic nhau, kich thudc khoang 4-5 ym. Sy hen kit kem giira nhya nin v i OGyp la kha ro, phin anh kha ning kit dinh va tuang hgp thip giiia PP vi OGyp, vin dl nay se giy ra cac khuyit tit cho vgt li?u compozit ' PP/OGyp. Hinh 6(b) cho thay cac hat MGyp phan tan tren nen nhya PP ddng diu, sy phan bd kich thudc cac hat MGyp nhd ban so vdi cic hat OGyp, the hien sy ket dinh chit che giira pha phin tan va nhya nin. Ket qui nay cho thiy kha nang tuang hgp giiia pha nhya nen vi pha phan tan da dugc cii thi?n ding ke nhd vai trd ciia SDS. Dilu nay da giii thich sy gia tang gii tri dp ben keo dih va md dun dan hoi cua cac mau PP/MGyp so vdi mau compozit PP/OGyp.
Hinh 6: Anh FE-SEM cua (a) PP/OGyp (95/5) va (b) PP/MGyp (95/5)
4. KET LUAN
Trong nghien ciru nay, chiing tdi da bien tinh hat Gyp phe thai bdi chat hogt dpng b l mat SDS bing phuang phip ndng chay. Phd hong ngogi FT-IR da niinh chimg sy ket dinh ciia hgp chit SDS tren be
mat hgt Gyp. Tir kit qua TGA, ham lugng SDS di bam len bl mat la 0,73 % dgt hipu suit biln tinh 19%. Ket qui khio sat tinh chat ca ly cho thiy, vgt lipu PP/MGyp cd dg bin keo dut giam chgm ban so vdi miu PP/OGyp khi ting him lugng pha phin tan.
Gii tri md dun din hdi ciia compozit PP/MGyp
TCHH, T. 52(1), 2014
75/25 dat 1087 MPa, tang 40 % so vdi nhya PP ban dau. Hinh diai cau tnic cua compozit quan sat tren inh FE-SEM eho thiy sy phin tin ddng deu ciia hat MGyp va ket dinh tdt tren nen PP nhd vai trd ciia chit blln tinh b l mgt SDS.
Viy viec su dyng hgp chat SDS de bien tinh hgt Gyp phe thii va che tgo vat lieu polyme compozit vdi cac tinh chat ca !y tdt cd thi md ra hudng irng dung sin xuat logi vgt lieu niy vdi quy md ldn che tao cac san phim cdng nghiep vi din dung, gdp phan giim gia thanh sin xuit va hgn che d nhiem mdi trudng.
LM cam on: Nghien ciru ndy duac thuc hiin vdi su hd tr^ ciia Cdng ty DAP Vinachem Viet Nam, Hdi Phdng.
Nguyen Vd Giang vd cpng su natural gypsum. Vibrational Spectroscopy, SO, 226- 230 (2009).
t. Nguyen Vu Giang and Myung Yul Kim Tlie effect of stearic acid coating on waste-gypsum filler m PVC/waste-gypsum composites, H6i nghj khoa hoc lin thu 20, DHBK Ha Npi, 237-241 (2006).
5. Nguyen Vu Giang, Thai Hoang, Myung Yul Kim.
Surface modification of waste-gypsum fillers in PVC/waste-gypsum composites. Fourteenth intemational conference on composites/nano engineering. Colorado, USA, July 2-8, 467-468 (2006).
6. Ramsay, JA. A new method of freezing-point determination for small quantities. J. Exp. Biol, 26 (1), 57-64, PMID 15406812 (1949).
TAI LIEU THAM KHAO
1. ZH. Liu, KW. Kwok, RKY. Li, CL. Choy. Effects of coupling agent and morphology on the impact strength of high density polyethylene/CaC03 composites. Polymer, 43(8), 2501-2506 (2002).
2. EM. El Afifi, MA. Hilal, MF. Attallah and SA. EL- Reefy. Characterization of phosphogypsum wastes associated with phosphoric acid and fertilizers production, Joumal of Environmental Radioactivity, 100(5). 407-412 (2009).
3. G. Anbalagao, S. Mukundakumari, K. Sakthi Murugesan, S. Gunasekaran. Infrared, optical absorption, and EPR spectroscopic studies on
7. Nguyin Vii Giang, Trin Huu Trung, Mai Diic Huynh, Khuong Viet Ha. Tdng hap vd biin tinh canxi sunfat iing dung trong che tgo vdt lieu compozit. Tap chi Hoa hpc, 50(5B), 204-209 (2012).
S. Dr. (Mrs.) Saswati Ghosh under guidance of Prof Bamn Gupta. Determination of Gypsum Content in Building Materials by Thermo gravimetric Method, Posted on April 10th (2012).
9. GHA. van der Heijden, L. Pel, HP. Huinink. K.
Kopinga. Moisture transport and dehydration in heated gypsum, an NMR study. Chemical Engineering Science, 66, 4241-4250 (2011), 10. Per Almen and Inger Ericsson. Quantification of
Sodium Dodecyl Sunfate in a Two-Phase System Using Filament-Pulse-Pyrolysic-Cas Chromatography, Lsngmuii, 11, 108-110(1995).
Lien hi: Nguyen Vfl Giang Vien Ky thuat nhiet ddi,
Vien Han lim Khoa hgc va Cdng nghe Viet Nam Sd 18, Dudng Hoing Qudc Viet, Qugn Ciu Giiy, Ha Ngi Email: [email protected].
106
