Download - Ky Thuat Gia Cong Polyme
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K THUT GIA CNG POLIME
Ging vin: Hong Hi Hin
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Chng 1. Gii thiu chung
I. Cc mi quan h trong gia cng vt liu
1. Mi quan h gia cng
Vt liu Thit b
Sn phn
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1.1. Quan h sn phm vt liuS la chn vt liu dng gia cng ph thuc:
- Tnh cht s dng- iu kin s dng- Yu t kinh t: gi c
- Hnh dng sn phmTnh cht ca vt liu quyt nh- Tnh cht ca sn phm- iu kin s dng sn phm
- Chi ph gi thnh sn phm- Tnh cht ca vt liu
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1.2. Quan h sn phm thit b gia cng
S la chn thit b gia cng ph thuc:
- Hnh dng sn phm- Yu cu chnh xc kch thc sn phm
- Yu t kinh t: sn lng, gi c
- Phng php gia cng v iu kin gia cng nhhngrtnhiun tnh chtsnphm. tcmtsnphmchtlng cao cnphi c:
+ Mtphng php thch hp,+ Thitbttkthp
+ Viclachn cc iukin gia cng tiu.
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1.3. Quan h vt liu thit b gia cngTnh cht nhit v tnh cht lu bin ca vt liuquyt nh:
- Vic chn la thit bgia cng
- L iu kin quan tm khi thit k khun
- Vic xc nh cc thng s gia cngMiphng php gia cng c cc c trng ring
bitch ph hpvimtsloi nguyn liu. V vy
slachn nguyn liucn ch nphng phpgia cng.
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2. Mi quan h gia cht lng sn phm
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Tnh chtcasnphmchunhhngrtnhiubitnh chtcavtliuemi gia cng.
i vi polime ngoi tnh chtca nguyn liu cnch n tnh chtcaph gia v cng thc pha chchng.
Cc thng s gia cng nhnhit, p sut,thi giannh hng trc tip n vic gia cng polime. Ccthng s ny c thdin tc cc i lngnhvntc,onng di chuyn.
nhyca cc thitbcmng,s chnh xc cathitb gia cng ng vai tr quan trng trong thnhcng camtsnphm.
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II. Cc phng php t nng nguyn liu1. t nng b mt
y l phng php thng c s dng- Tc truyn nhit ph thuc vo din tch b
mt vt liu tip xc vi ngun nhit.
- Nhit b mt vt liu cao hn bn trong,ph thuc tnh cht ca vt liu
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2. t nng ni
a.tnngbngdngin cao tn:
- p dng cho polime phn cc.
- Di tc dngca dng in cao tn cc lng
cccavtliuschuynng lin tc v doc strgiachuynngca cc lngccny theo s thay i in trng xoay chiutrong vtliushpthnnglng v chuyn
thnh nhitnng lm nng vtliu.
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b. t nng bng siu m
- Vt liub tc ngbi sng siu m, bindng v hiphc lin tc.
- Do tnh chtcavtliu c spngtri
vi tc ng c hc nn vt liu s hp thunng lng v chuyn thnh nhit nng lmnng vtliu.
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c. t nng bng ma st nht
- Polime c nht cao chy trong cc rnh vit,khun to ma st v sinh nhit t nngpolime
- Ch , nhit ny c th tng cao qu lmphn hyvtliu
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III. c tnh lu bin ca polime- Do c imbt i xng hnh hc ca phn t
polime chiu di ln hn rt nhiu so vi chiurng, do trong qu trnhbindnghocchy phnt polimeb ko cng theo chiu tc dnglc,y lqu trnh nhhng phn t.
- Cc phn tb ko cngtrng thi nnglng caoc khuynh hng hiphc tr v trng thi nnglngthp gy nn s co rt vtliu sau khi gia cng.
- Trong khi gia cng nhit cao nn cng phn
no ph vcs ko cng ny.- Nhit cng cao, nht vt liu cng cao th s
nhhng phn t cng chimuth.- V thcn quan tm n cc thng s gia cng
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IV. Nhng tnh cht k thut ch yu ca vt liu polime
1. Khi lng ring gp
- c trng cho s y vt liu- Ph thuc vo s sp xp cht kht ca vt liu
- Thng s cn thit thit k khoang np liu,
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2. H s nn p (K)
- K th hin s bin i th tch vt liu khi a vo gia
cng.
- K ph thuc vo p sut nn, nn
- K l thng s quan trng trong thit k my n
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3. Thnh phn c ht kch thc ht
- i vi vt liu dng ht th thng s ny rtquan trng.
- Kch c ht c xc nh bng phng phpry.
- Kch thc ht ca nguyn liu nh hng trctip n qu trnh gia cng nh pha trn, gianhit,
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4. Hm lng m v cc cht d bay hi
- Hm lng m v cc cht d bay hi nhhng ln n qu trnh gia cng cng nhchtlngsnphmnh:
+ Tobmtsn si, snphm cong vnh,
+ Ko di thi gian gia cng, thi gian p,
- Hm lngmc xc nhbngtskhilngcamutrc v sau khi sy.
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5. linh ng
- linh ng l mti lngc trng chokhnngchycavt liudi tc dngcap sut v nhit.
- linh ngphthuc:
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Xc nh linh ng bng cc phng php:a. Phng php Rasiga
- Khun Rasiga c tit din hnh elip u trn cngc kch thc 4x6mm, u di c kch thc1x4mm chiu cao 250mm.
Cch xc nh:
- p vt liu thnh ming nhit thng, p sut500kg/cm2
- Ly 7,5g vt liu sau khi p cho vo khun, cho vokhun v gia nhit n 150-160oC
- p di p sut 300kg/cm2 trong vng 3 pht- Chiu cao ca thanh th hin linh ng ca vt
liu
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b. Phng php dng nht k mao qun p sut khng i
- L phng php o khi lng cht do chy qua
mao qun p sut khng i trong vng 10 pht
c. o bng do k
- S dng do k walace- S dng nht k Mooney
ng dng trong cht do v cao su
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6. Vn tc ng rn v thi gian ng rn
- Thi gian ngrncanha hay thi gian luha ca cao su l thi gian cnthitvtliuchuynv trng thi c tnh cht s dng ttnht
- Vn tcng rnph thucbnchtcavtliu, dy snphm.
- Thi gian ng rn c obng nht k
canavec, thi gian lu ha cao su c obnglu ha k v nhtk Mooney
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7. co th tch
- co th tch bindinsgim th tch casnphm so vi kch thc khun sau khi ttinhit bnh thng.
- co th tch c nh hng tri ngc nhau:+ Gy ra s thiu th tch ca sn phm
+ Gy ra s cong vnh, rn nt ca sn phm
+ Lm d dng ly sn phm ra khi khun
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Nguyn nhn
- S gin n nhit ca sn phm
- Do phn ng ng rn xy ra trong nha nhit
rn lm co rt th tch
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Cc yu t nh hng n co th tch
Bn cht ca polime S hin din ca cc cht n thng lm
gimth tch
iukin gia cng nhnhit,thi gian Bnchtvtliu lm khun
S mt m v cc cht d bay hi trong qu
trnh gia cng
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8. Nhit gia cng
Nhit gia cng ph thuc vo:
- Bn cht polime
- Cc tnh cht gia cng ca polime
- Hnh dng v kch thc sn phm- Phng php v loi thit b dng gia cng
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Mt s im lu khi chn nhit gia cng
1. i vi nha nhit rn v cao su chng tachn trn vntcngrn ph hpviiukinthitb v c tnh casnphm.
2. ivinhanhitdo chng ta da trn ccthng s nh nhit chy nht, nhit thy tinh ha, nhit phn hy. Nhit gia cng phi ln hn nhit chy nht
nhng b hnnhit phn hy, tg cn l thngs quan trnglysnphm ra khi khunphi b hn tgt 20-30oC
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V. Phn loi cc phng php gia cng1. Phn loitheo chcnng
- Nhm to hnh nhit:+Nhimvto hnh snphm,+ Nhm ny bao gm gnht cc phng php giacng nh: c p, n, p phun, to hnh nhit, khun,
- Nhmbin tnh: l ccphng php lm thay i tnhchtcavtliu,snphmnh: trn, ko cng,x l
bmt- Nhm to lin kt: l cc phng php lin kt cc
chi titto thnh snphmnh: hn v dn
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2. Phn loi theo iukin gia cng v trng thi vtliu
- Nhm 1: Vtliuc gia cng nhit cao, p sut cao v
trng thi chynht. V d: n,c p, p phun,- Nhm 2: Vtliuc gia cng nhit trung bnh, p sut
trung bnh v trng thi cao su. V dnhto hnh nhit
- Nhm 3: Vt liu c gia cng nhit thng, p sut
thng v trng thi rn. V d: gia cng ckh- Nhm 4: Vt liuct nng chy v rt vo khun nh
hnh
- Nhm 5: Vtliutrng thi lngnhitthngc rt
vo khun v ng rnngui. V d: gia cng cc loinhaepoxy, poliester, PMMA, MMA