ky thuat gia cong polyme

7/28/2019 Ky Thuat Gia Cong Polyme

1/27

K THUT GIA CNG POLIME

Ging vin: Hong Hi Hin


2/27

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


9/27

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

ky thuat gia cong polyme

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