Dab tsi yog cov ntu ntawm cov ntsia hlau?

Thaum cov khoom txav mus rau pem hauv ntej ntawm cov ntsia hlau, nws muaj kev hloov pauv ntawm qhov kub thiab txias, siab, viscosity, thiab lwm yam. Raws li kev hloov pauv ntawm cov khoom siv, cov ntsia hlau tuaj yeem muab faib ua ntu pub (pub), ntu compression, thiab ntu compression. seem thiab homogenization seem.
①. Plastics thiab peb lub xeev ntawm plastics
Muaj ob pawg ntawm cov yas: thermoset thiab thermoplastic. Tom qab thermoset yas molded thiab solidified, nws tsis tuaj yeem rhuab thiab melted rau molding. Cov khoom tsim los ntawm cov yas thermoplastic tuaj yeem rov ua dua thiab yaj los ua lwm yam khoom.
Raws li qhov kub thiab txias hloov, cov yas thermoplastic tsim cov kev hloov pauv peb lub xeev: lub xeev iav, lub xeev elastic heev thiab lub xeev khov. Raws li qhov kub thiab txias hloov ntau zaus, peb lub xeev hloov ntau zaus.
ib. Cov yam ntxwv sib txawv ntawm polymer yaj hauv peb lub xeev:
Glassy xeev - cov yas zoo li cov khoom khov; Lub thermal kinetic zog yog me me, lub zog intermolecular yog loj, thiab lub deformation yog feem ntau pab los ntawm daim ntawv cog lus lub deformation; lub deformation rov qab instantaneously tom qab lub sab nraud quab yuam raug tshem tawm, uas yog ib tug dav elastic deformation.
Lub xeev elastic heev - cov yas zoo li cov khoom zoo li roj hmab; lub deformation yog pab los ntawm conformational stretching ntawm macromolecules tshwm sim los ntawm saw segment orientation, thiab deformation tus nqi yog loj; Lub deformation tuaj yeem rov qab los tom qab lub zog sab nraud raug tshem tawm tab sis yog nyob ntawm lub sijhawm, uas yog qhov deformation heev elastic.
Viscous flow state - yas tshwm raws li cov kua nplaum heev; thermal zog ntxiv intensifies tus txheeb ze swb txav ntawm saw molecules; Lub deformation yog irreversible thiab belongs rau yas deformation
b. Plastic processing thiab peb lub xeev ntawm cov yas:
Cov yas tuaj yeem ua tshuab thaum nyob hauv lub xeev iav. Nyob rau hauv lub xeev siab elastic, nws tuaj yeem ncab thiab ua tiav, xws li hlau kos duab, extrusion, tshuab molding thiab thermoforming. Nyob rau hauv lub viscous flow xeev, nws muaj peev xwm ua tiav los ntawm txheej, rotational molding thiab txhaj tshuaj molding.
Thaum qhov kub siab tshaj qhov dej khov hauv lub xeev, cov yas yuav thermally decompose, thiab thaum kub qis dua lub xeev iav, cov yas yuav nkig. Thaum cov yas kub siab tshaj qhov dej khov hauv lub xeev los yog qis dua lub xeev iav, cov yas yas thermoplastic feem ntau ua rau tsis zoo thiab raug puas tsuaj, yog li ob qhov chaw kub no yuav tsum zam thaum ua lossis siv cov khoom yas.
②. Peb-theem ntsia hlau
Muaj peb lub cev lub cev ntawm cov yas hauv lub extruder - lub xeev iav, lub xeev elastic heev thiab lub xeev khov. Txhua lub xeev muaj cov kev cai sib txawv rau cov qauv ntsia hlau.
c. Txhawm rau hloov mus rau cov kev xav tau ntawm cov xeev sib txawv, cov ntsia hlau ntawm extruder feem ntau muab faib ua peb ntu:
Kev pub mis L1 (tseem hu ua khoom xa khoom seem)
Melting section L2 (hu ua compression section)
Homogenization seem L3 (hu ua metering seem)
Qhov no feem ntau hu ua peb-theem ntsia hlau. Cov txheej txheem extrusion ntawm cov yas hauv peb theem no txawv.
Kev ua haujlwm ntawm ntu pub mis yog xa cov khoom siv los ntawm lub hopper mus rau ntu compression. Cov yas feem ntau tseem nyob hauv ib lub xeev ruaj khov thaum lub sij hawm txav mus thiab yog ib nrab yaj vim yog cua sov. Qhov ntev ntawm ntu pub mis nws txawv nrog hom yas, thiab tuaj yeem pib tsis deb ntawm lub hopper thiab xaus ntawm 75% ntawm tag nrho qhov ntev ntawm lub khob hau.
Feem ntau hais lus, extruded crystalline polymers yog qhov ntev tshaj plaws, ua raws li tawv amorphous polymers, thiab mos amorphous polymers yog luv tshaj. Txij li thaum ntu pub mis tsis tas yuav tsim compression, qhov ntim ntawm cov ntsia hlau zawj tuaj yeem nyob tsis hloov. Qhov loj ntawm lub kaum sab xis helix muaj kev cuam tshuam ntau dua rau kev pub noj muaj peev xwm ntawm ntu no, uas cuam tshuam rau kev tsim khoom ntawm extruder. Feem ntau, lub kaum sab xis ntawm cov khoom siv hmoov yog li 30 degrees, uas muaj qhov ua tau zoo tshaj plaws. Lub kaum sab xis ntawm cov ntaub ntawv square yuav tsum yog li 15 degrees, thiab lub kaum sab xis ntawm cov ntaub ntawv kheej kheej yuav tsum yog li 17 degrees.
Main parameters ntawm cov ntsia hlau nyob rau hauv qhov chaw pub mis:
Lub kaum sab xis ψ feem ntau yog 17 degree ~ 20 degree .
Cov ntsia hlau zawj qhov tob H1 yog xam raws li qhov sib piv ntawm geometric compression piv ε ntawm cov ntsia hlau tom qab txiav txim siab cov ntsia hlau zawj qhov tob hauv seem homogenization.
Qhov ntev L1 ntawm ntu pub mis yog txiav txim siab los ntawm cov qauv empirical:
Rau amorphous polymer L1=(10%-20%)L
Rau crystalline polymer L1=(60%-65%)L
Kev ua haujlwm ntawm qhov compression seem (migration section) yog ua kom cov khoom siv, hloov cov khoom los ntawm cov khoom mus rau molten, thiab tshem tawm cov huab cua hauv cov khoom; txhawm rau hloov pauv cov roj hauv cov khoom siv rov qab mus rau qhov chaw pub mis, compacting cov khoom thiab txo qhov ntim ntawm cov khoom thaum nws melts. Vim nws qhov me me, qhov seem ntawm cov ntsia hlau yuav tsum tsim ntau dua shearing thiab compression ntawm cov yas. Vim li no, qhov ntim ntawm cov ntsia hlau channel feem ntau yog maj mam txo, thiab cov qib ntawm kev txo qis yog txiav txim siab los ntawm qhov compression tus nqi ntawm cov yas (qhov tshwj xeeb lub ntiajteb txawj nqus ntawm cov khoom / pom meej lub ntiajteb txawj nqus ntawm cov yas). Qhov sib piv compression tsis tsuas yog cuam tshuam nrog tus nqi compression ntawm cov yas, tab sis kuj rau cov duab ntawm cov yas. Cov hmoov muaj lub ntiajteb txawj nqus me me thiab ntau cov cua nkag, yog li nws yuav tsum muaj qhov sib piv loj dua (txog 4 ~ 5), thaum cov pellets tsuas yog 2.5 ~ 3.
Qhov ntev ntawm qhov compression seem yog feem ntau cuam tshuam nrog lub melting point thiab lwm yam khoom ntawm cov yas. Cov yas uas muaj qhov kub thiab txias ntau yam, xws li polyvinyl chloride, uas pib yaj saum toj 150 degree, muaj qhov ntev tshaj plaws compression seem, ncav cuag 100% ntawm tag nrho cov ntsia hlau ntev (gradient hom), thiab polyethylene nrog ib tug nqaim melting kub ntau yam (tsawg kawg). density polyethylene 105 ~ 120 degree, high-density polyethylene (125 ~ 135 degree), thiab lwm yam, lub compression seem yog 45 ~ 50% ntawm tag nrho cov ntev ntawm cov ntsia hlau; polyamide, seem compression tsuas yog ib lub suab ntev.
Main parameter ntawm melting seem ntsia hlau:
Compression ratio ε: feem ntau yog hais txog geometric compression piv, uas yog qhov piv ntawm qhov ntim ntawm thawj zawj hauv cov ntsia hlau pub rau qhov ntim ntawm qhov kawg zawj hauv seem homogenization.
ε=(Ds-H1)H1/(Ds-H3)≈H1/H3
Hauv cov qauv, H1 - qhov tob ntawm thawj qhov ntsia hlau zawj hauv ntu pub
H3--Qhov tob ntawm qhov zawj kawg hauv seem homogenization
Lub melting seem ntev L2 yog txiav txim los ntawm tus qauv empirical:
Rau amorphous polymer L2=55% ~ 65%L
Rau crystalline polymers L2=(1-4)Ds
Lub luag haujlwm ntawm homogenization seem (kev ntsuas seem) yog pub cov khoom molten rau hauv lub tshuab taub hau ntawm qhov ntim tas li (ntau npaum li cas) thiab lub siab tsis tu ncua los tsim nws hauv qhov tuag. Cov channel ntim ntawm seem homogenizing yog tas li raws li qhov chaw pub mis. Txhawm rau tiv thaiv cov ntaub ntawv los ntawm kev khaws cia rau hauv lub kaum sab xis ntawm lub taub hau tuag thiab ua rau decomposition, lub taub hau ntsia hlau feem ntau tsim los rau hauv lub khob hliav qab lossis lub voj voog; lub homogenizing seem ntawm ib co screws yog ib tug pas nrig nrog ib tug tag nrho du nto hu ua lub taub hau torpedo, tab sis kuj muaj engraved sawv daws yuav. Grooved los yog milled rau hauv cov qauv. Lub taub hau torpedo muaj kev ua haujlwm ntawm nplawm thiab tswj cov khoom siv, tshem tawm qhov tshwm sim ntawm lub sijhawm khiav, thiab ua kom lub siab ntawm cov khoom, txo cov thickness ntawm cov khoom txheej, txhim kho cov cua sov, thiab ntxiv kev txhim kho plasticizing efficiency ntawm cov ntsia hlau. . Ntu no tuaj yeem yog 20 mus rau 25% ntawm tag nrho qhov ntev ntawm cov ntsia hlau.
Cov tsis tseem ceeb ntawm cov ntsia hlau nyob rau hauv homogenization seem:
Cov ntsia hlau zawj qhov tob H3 yog txiav txim los ntawm cov qauv empirical H3=(0.02-0.06)Ds
Qhov ntev L3 yog txiav txim los ntawm cov qauv hauv qab no L3=(20%-25%)L
d. Raws li txoj kev xav ntawm kev thauj mus los yaj, muaj plaub hom yaj ntws hauv cov ntsia hlau homogenization seem. Cov dej ntws ntawm cov khoom molten nyob rau hauv cov ntsia hlau zawj yog ib qho ua ke ntawm plaub qhov dej ntws:
Forward flow - qhov ntws ntawm cov yas yaj ntawm lub thoob thiab cov ntsia hlau raws li qhov zawj kev taw qhia mus rau lub taub hau tshuab.
Counter Flow - cov kev taw qhia ntws tawm yog qhov sib txawv ntawm qhov ntws mus rau pem hauv ntej, tshwm sim los ntawm lub siab gradient tshwm sim los ntawm kev ua haujlwm ntawm lub taub hau tshuab, ntxeem tau phaj, lim phaj, thiab lwm yam.
Hla ntws - ntws ntawm yaj raws cov kev taw qhia perpendicular mus rau cov xov phab ntsa, cuam tshuam rau kev sib tov thiab tshav kub pauv ntawm cov yaj thaum lub sij hawm extrusion txheej txheem.
Leakage flow - lub backflow tsim nyob rau hauv qhov sib txawv ntawm cov ntsia hlau thiab chim vim lub siab gradient, raws li axial kev taw qhia ntawm cov ntsia hlau.
2. Cov qauv ntawm cov ntsia hlau zoo tib yam
Pa tag nrho threaded peb-section screws tuaj yeem muab faib ua peb daim ntawv raws li kev hloov hauv xov nqa thiab zawj qhov tob:
(1) Sib npaug spaced qhov tob ntsia hlau
Qhov ceev ntawm qhov sib npaug qhov tob-hloov cov ntsia hlau los ntawm qhov zawj qhov tob tuaj yeem muab faib ua ob hom:
① Equidistant gradient ntsia hlau: Ib tug ntsia hlau uas nws qhov tob yuav maj mam ua ntiav los ntawm cov khoom noj mus rau qhov kawg ntsia hlau zawj hauv seem homogenizing. Tshaj qhov ntev melting seem, qhov zawj qhov tob yuav maj mam ua ntiav.
② Isometric mutation ntsia hlau: uas yog, cov ntsia hlau groove qhov tob nyob rau hauv seem noj thiab homogenization seem tseem tsis hloov, tab sis qhov zawj qhov tob hauv seem melting dheev ua ntiav.
(2) Tsis tu ncua qhov tob sib txawv pitch ntsia hlau
Qhov tob qhov sib txawv ntawm qhov sib txawv pitch ntsia hlau txhais tau hais tias qhov tob ntawm cov ntsia hlau zawj tseem tsis hloov pauv, thiab cov ntsia hlau pitch maj mam nqaim los ntawm thawj cov ntsia hlau zawj hauv ntu pub rau qhov kawg ntawm seem homogenization.
Cov yam ntxwv ntawm qhov sib txawv ntawm qhov sib txawv ntawm qhov sib txawv pitch ntsia hlau yog vim qhov tob ntawm cov ntsia hlau zawj, qhov ntu ntu ntawm cov ntsia hlau ntawm qhov chaw noj mov yog qhov loj dua thiab muaj lub zog txaus, uas yog qhov tsim nyog rau kev sib hloov ceev, yog li ntawd txhim kho cov khoom tsim tau. Txawm li cas los xij, kev ua cov ntsia hlau yog qhov nyuaj, qhov ntws ntawm cov dej ntws rov qab yog qhov loj, thiab cov nyhuv homogenization tsis zoo, yog li nws tsis tshua siv.
(3) Qhov sib txawv qhov tob thiab sib txawv pitch ntsia hlau
Qhov sib txawv ntawm qhov tob thiab qhov sib txawv pitch ntsia hlau yog hais txog cov ntsia hlau uas nws qhov tob qhov tob thiab xov nqa lub kaum sab xis maj mam hloov los ntawm qhov pib ntawm ntu pub rau qhov kawg ntawm homogenization, uas yog, cov xov nqa tau maj mam dhau los ntawm qhov dav, thiab cov ntsia hlau zawj. qhov tob yuav maj mam dhau los ntawm qhov tob. Cov ntsia hlau no muaj cov yam ntxwv ntawm ob lub ntsej muag dhau los, tab sis nws nyuaj rau tshuab thiab tsis tshua siv.
3. Cov khoom siv ntsia hlau
Cov ntsia hlau yog ib qho tseem ceeb ntawm cov extruder. Cov khoom siv ntsia hlau yuav tsum muaj cov yam ntxwv ntawm qhov kub thiab txias tsis kam, hnav tsis kam, corrosion kuj, siab zog, thiab lwm yam. Nws yuav tsum muaj kev ua haujlwm zoo, kev ntxhov siab me me tom qab kev kho cua sov, thiab thermal deformation me me.
Rau cov khoom ntawm extruder ntsia hlau, muaj cov hauv qab no tshwj xeeb yuav tsum tau:
① High mechanical zog. Nws yuav tsum muaj lub zog txaus los hloov mus rau qhov kub thiab txias ua haujlwm siab thiab ua kom lub neej ua haujlwm ntawm cov ntsia hlau.
② Kev ua haujlwm zoo txhua yam. Nws yuav tsum muaj kev txiav zoo dua thiab kev kho cua sov ua haujlwm.
③ Zoo corrosion kuj thiab tiv thaiv hnav.
④ Yooj yim kom tau cov ntaub ntawv.