Chuong 8-Vat Lieu Chat Deo

7/30/2019 Chuong 8-Vat Lieu Chat Deo

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Bi gingVt Liu Xy Dng

CHNG 8 VT LIU CHT DO

8.1. NGUYN LIU CH TO VT LIU CHT DO

Cht do l tn gi ca mt nhm vt liu cht hu c (nhn to hoc thinnhin), m cc cao phn t polime-l thnh phn chnh ca n, c kh nng tohnh di tc dng ca nhit v p sut v sau vn gi nguyn c hnhdng . Thnh phn ca cht do nh sau: cht kt dnh (polime), cht n (btv c hoc hu c, si vi, vy), cht ho do ( ci thin cho kh nng to hnhcho cht do), cht rn nhanh v cht to mu. Cu trc v tnh cht ca cht do,ngoi polime cn ph thuc vo cc cu t khc.

Phn loi cht do

Theo tnh cht c l:+ Cht do cng: l vt liu n hi rn, cu trc v nh hnh.+ Cht do bn cng l vt liu n hi rn cu trc tinh th.+ Cht do mm l vt liu mm v nh hi.+ Cht n hi.

Theo tnh cht c lin quan n nhit+ Vt liu do nng+ Vt liu cng nng

8.1.1. Cht kt dnh (polime)

Cht kt dnh (polime) s dng trong cng nghip sn xut cht do xy dngnhn c bng phng php tng hp t cc cht n gin (n phn).

Theo phng php sn xut chng c chia ra hai nhm:

Nhm A l nhng polime trng hp (polistiron, polietylen, poliizobutilen, polimetylmentarilat) ch yu c sn xut bng phng php trng hp chui.

Nhm B l nhng polime (fenol - fomandehyt, motrevin - foman dehyt,epoxy, poliamit...) c sn xut bng phng php trng ngng v trng hpphn on.

Theo cu to bn trong polime c phn ra: loi mch thng v mchkhng gian (c lin kt li v lin kt ngang). Cc cao phn t ccu trc mch thng (polietilen, polivinylclorit, polistiron) b mm ra khi nungnng v cng rn li khi lm ngui. l cc cht do nng. Loi polime nyu b trng n hoc b tan trong cc dung mi khc nhau. Cc cao phn tc cu trc mng li khng gian l nhng cht rn dng thu tinh, khng tanv khng chuyn thnh trng thi do khi nung nng.

GVC.Ths Trng Th Kim Xun - 1 -


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8.1.2. Cht n

Cht n thng dng bt, si v vy. Cht n dng bt (bt thch anh, phn, barit, hot thch v cc cht bt hu c) to cho cht do nhiu tnh cht cgi tr (bn nhit, bn axit,v.v...) v cng c th nng cao cng, tng bn lu,gim gi thnh. Cht n ang dng si (si aming, g thu tinh) c s dngkh rng ri, lm tng cng , gim gin tng bn nhit v bn va pcho cht do. Cht n dng vy (giy, vi bng, vi thu tinh, cactng aming,dm bo g,...) cng lm tng cng cht do.

8.1.3. Cht ho do

Cht ho do l nhng cht lm tng tnh do cho cht do. Chng cnphi tr v mt ho hc, t bay hi v khng c. Nhng cht ho do hay dng laxit zinkit, stearat nhm v.v...

8.1.4. Cht to mu

Cht to mu to cho cht do mu sc nht nh. Chng cn phi n nh theothi gian, khng bin mu di tc dng ca nh sng. Cc cht to mu thngdng l cc loi bt mu hu c (nigrozin, crizoidin v.v...) v c bt mu v c (tson, oxit ch, oxit crm, untra marin,v.v...).

8.1.5. Cht xc tc

Cht xc tc c tc dng rt ngn thi gian rn chc ca cht do, th d i vifenol-femaldehyt ngi ta hay dng vi v urotropin.

8.1.6. Cht n nh

Cht n nh c kh nng gi cho cu trc v tnh cht ca cht do khng b bini theo thi gian do tc dng ngn nga s ho gi sm di s tc dng canh sng mt tri, oxy ca khng kh, nung nng v cc tc dng khc.

8.1.7. Cht bi trn

Cht bi trn dng bi khun lm cho cht do khng b dnh vokhun, th d nh cc cht stearin, axit oleic, v.v... sn xut do xp, ngi tacon s dng cht to rng, to ra l rng trong vt liu.



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8.2. CC TNH CHT CH YU CA VT LIU CHT DO

Cht do c nhiu tnh cht qu bu, cc ch tiu c l cao. Khi lng th tchdao ng trong khong 10-2200kg/m3, khi lng ring 0,9-2,2g/cm3. Cht do c

cht n dng bt v dng si cng nn t n 1200-2000kG/cm

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.Cng chu un ca cht do c cht n dng vy t n 1500kG/cm 2, ccht n dng si thu tnh d hng : 4800-9500kG/cm 2. H s phm cht ktcu ca cht do ln 2250kG/cm2, trong khi thp l 127kG/cm2, ura1613kG/cm2.

Cht do khng b n mn. Ni chung n bn vi dung dch axit v kim yu. Cmt s cht do (th d polyetilen, poliisobutilen, polistiron, polivinyl clorit) thm chcn bn vi c dung dch axit, mui v kim c. V vy cht do c s dngrng ri trong xy dng cc x nghip ho cht, h thng thot nc v bo vin.

Cht do, bnh thng l vt liu dn nhit km (= 0,28-0,65kcal/m.oC.h). Chtdo bt v cht do kh dn nhit cn km hn na (=0,05-0,24 kcal/m.oC.h). Vth cht do c s dng rng ri lm VLCN.

Cht do t b mi mn, nn n thch dng vic tri sn nh, c trong sut cao.Knh hu c ch cho tia t ngoi i qua di 1%, trong khi knh thng l hn70%.

Cht do c th nhum thnh cc mu sc bt k. Khi s dng nhng cht to

mu bn vng chng c th gi c mu sc rt lu, nn khng phi sn nhk. Cht do rt d gia cng thnh cc sn phm c hnh dng phong ph, thmch rt phc tp bng cc phng php rt, p, n. Nhiu loi cht do cn rtd hn nh ngi ta c th sn xut cc loi ng ng phc tp, cc loi lcha. Hn c th c thc hin bng nhng thit b n gin vi s tham giaca kh nng (th d CO2) nhit 150 - 200oC.

Mt u im na ca cht do l ngun nguyn liu v tn. Chng c th nhnc t nhiu cht ho hc, th d: than , du m, g, vi, kh, khng kh, v.v...

Tuy vy cht do cng c nhiu nhc im. a s cht do c tnh bn nhitkhng cao (70-200oC), ch c mt s loi cht do (silic hu c,politetrafloetilen) c th lm vic nhit 250 oC. Cht do c cng khngln. Th d cht do polistiron, cht do acrilat c cng (theo phng phpBrinen) khong 1500 kG/cm2, cn cht do tectolit-3500, cht do c h s nnhit ln (25 - 120).10-6 trong khi thp l 10.10-6. Chng c tnh t bin ln,



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trong vi ti trng khng i theo thi gian chy do pht trin ln hn rtnhiu so vi mt s vt liu khc (thp, b tng).

Theo thi gian mt s cht do b ho gi, cng v cng gim, tnh ginxut hin, bin mu. S ho gi xy ra di tc dng ca nh sng, khng kh vnhit . Khi t chy nhiu cht do tch ra cc cht kh c.

8.3. CC SN PHM CA VT LIU CHT DO

Vt liu v sn phm cht do c chia ra: vt liu lt sn, honthin tng trong, trn v g; vt liu dng cho cc kt cu xy dng, cc snphm dng thanh v matt tng hp; vt liu cch nhit v vt liu cch m; vtliu lp, ngn nc v vt liu gn; cc thit b k thut v sinh, ng dn, vt liulm ct, sn tng hp.

8.3.1. Vt liu lt sn

Vt liu polime dng lt sn c tnh chng mi mn tt, t dn nhit, t htnc, khng trng n khi b m t, kh cng v bn, t bit l chtlng sn ph cao. C ngha l chng tho mn cc yu cu ca sn. Vt liu ltsn chia lm 3 nhm: vt liu cun, vt liu tm v vt liu to sn lin khi.

8.3.1.1. Vt liu cun

Vt liu cun ph sn c sn xut trn c s polime v cc cht n khc

nhau. Ngoi ra ngi ta cn cho thm cht ho do, cht to mu v cc chtph gia khc. Theo loi polime s dng phn ra: vt liu cun glip tan(polieste), polivinyl-clorit, cloxilin, cao su (relin) v cc vt liu cun khc.Theo cu to phn ra: vt liu khng c nn v vt liu c nn gia cng hoc nncch nhit, cch m, mt lp hoc nhiu lp, lp mi phng hoc mi ln sng,mi cong mt mu hoc nhiu mu.

Vi sn gliptan c sn xut t polime gliptan bin tnh, cht n (bt nt, btg), cht to mu v ph gia. Kch thc ca tm vi sn (dng cun) di 20mrng 1,8-2 m, dy 2,5 - 3mm. Vi sn c c trng bng cc ch tiu c l sau:

mi mn 0,06g/cm

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, ht nc sau 24 gi > 6 %, cng > 0,7mm (chiusu vt lm vin bi c ng knh 5mm di ti trng 100KG) v n hi

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