ThermoplasticKhoom siv- Cov yam ntxwv thiab cov khoom siv, cov khoom siv thermoplastic tau muab faib ua ob pawg loj raws li lawv cov kev tiv thaiv tshav kub thiab cov yam ntxwv: tshav kub- tiv taus cov thermoplastics thiab dav dav - lub hom phiaj thermoplastics.
Hom thiab cov khoom ntawm plastics:
△Thermodynamic hloov ntawm plastics
Thaum tshav kub kub- cov thermoplastics resistant tuaj yeem raug molded rau hauv ruaj khov- cov khoom yas ntawm qhov kub thiab txias, thiab tswj cov duab ruaj khov tom qab txias. Yog tias cua sov dua, lawv tuaj yeem muag thiab ntws, thiab muab molded rau hauv ruaj khov -zoo li cov khoom yas dua los ntawm kev rov ua dua - qhov no yog thim rov qab. Txij li cov ntaub ntawv thermoplastic tsis tau txais kev hloov pauv tshuaj lom neeg thaum lub sijhawm molding txheej txheem, cov khoom seem tuaj yeem rov ua dua thiab rov siv dua, hu ua "cov khoom siv thib ob" lossis "regrind."
Cov thermoplastics tau hloov pauv lub cev thaum lub sijhawm molding, txhais tau tias lawv tsis tuaj yeem hloov lawv lub xeev qub thaum rhuab, tab sis nyob twj ywm amorphous thiab tsis tuaj yeem ntws tom qab txias. Yog li ntawd, cov ntaub ntawv thermoplastic tsis tuaj yeem rov ua dua thiab rov ua dua, yog li cov khoom siv thermoplastic feem ntau tsis tuaj yeem rov qab siv dua.
Phau ntawv no feem ntau tham txog "yas" - tsis suav nrog roj hmab, uas kuj yog cov khoom siv thermoplastic.
Piv nrog cov txheej txheem yas molding, txawm hais tias kev txhaj tshuaj molding muaj ntau lub peev xwm tshwj xeeb thiab qhov zoo, nws kuj muaj qee qhov tsis xws luag thiab qhov tsis zoo. Nkag siab txog cov yam ntxwv tseem ceeb ntawm cov yas txhaj tshuaj molding yog qhov yuav tsum tau ua ua ntej thiab lav kom raug pwm tsim thiab kev txhim kho zoo ntawm cov pwm pwm.
(1) Shrinkage
Txawm hais tias cov khoom yas tuaj yeem tswj qhov kev ruaj ntseg nyob rau hauv qhov kub thiab txias thaum molded los ntawm cov pwm kab noj hniav thiab txias rau hauv chav tsev kub, qhov loj yuav me ntsis me dua cov pwm kab noj hniav qub. Cov yam ntxwv no yog hu ua shrinkage, uas tuaj yeem them nyiaj los ntawm molding kub tswj.
Qhov no shrinkage tsis tsuas yog tshwm sim los ntawm thermal expansion thiab contraction ntawm cov yas nws tus kheej, tab sis kuj muaj feem xyuam rau ntau yam txheej txheem molding thiab pwm tsim yam. Tom qab cov yas yog txias, qhov shrinkage tus nqi ntawm ib feem yog molding shrinkage, uas yuav txo tau los yog txhim kho los ntawm kev hloov cov txheej txheem tsis los yog me me hloov nyob rau hauv pwm kab noj hniav loj.
Cov khoom yas tau txais kev txo qis qis rau ib lub sijhawm tom qab molding, tseem hu ua post- molding shrinkage,thaum tuav tib lub molding tej yam kev mob:
① Lub shrinkage ntawm cov khoom yas tsis sib xws. Vim lub fact tias cov thermal shrinkage tus nqi ntawm plastics hloov nrog lub cev thiab tshuaj tej yam kev mob nyob rau hauv txawv sab hauv qhov chaw, lub shrinkage tus nqi ntawm cov yas qhov chaw tom qab txias rau chav tsev kub nws txawv nyob rau hauv loj thiab tsis yog tag nrho uniformity. Yog li ntawd, yuav tsum muaj qee qhov kev txwv ntawm kev molding qhov tseeb ntawm cov khoom yas, thiab qhov tseeb yuav tsum tau txhim kho kom tsim nyog los ntawm kev tsim pwm.
② Cov ncej -shrinkage ntawm yas qhov chaw. Thaum lub sij hawm molding txheej txheem, vim muaj ntau yam kev ntxhov siab sab hauv, tshuaj lom neeg cov tshuaj tiv thaiv, thiab ntau yam sab nraud quab yuam - feem ntau molding siab - cov yas seem tseem nyob tom qab molding nrog residual stress. Tom qab molding, vim muaj ntau yam teebmeem kev ntxhov siab, cov yas ib feem me me tseem hloov me ntsis tom qab ntau lawm. Feem ntau, feem ntau molded qhov chaw ruaj khov nyob rau hauv 10h tom qab molding, thiab yeej ruaj khov tom qab 24h, tab sis nws yuav siv sij hawm ntau tshaj 10 hnub rau lawv kom ruaj khov.Ua tib zoo saib thiab ua raws li kev ntsuas moldingyog tus yuam sij rau kev tswj cov ncej- molding shrinkage.
Txhawm rau kom ruaj khov qhov ntev kawg ntawm cov khoom yas tom qab molding, kev kho cua sov yog qee zaum xav tau tom qab molding. Kev kho cua sov tso cai rau cov thermoplastic khaws cia ntawm qhov kub thiab txias ua rau softening; tshem tawm sab nraud quab yuam ntawm molding shrinkage tso cai rau kev them nyiaj sab hauv kom zoo tshwm sim tom qab molding, uas tuaj yeem txo qhov ntev ntawm qhov molded ntawm qhov kub siab dua molding.
③ Directional shrinkage ntawm cov khoom yas. Thaum lub sij hawm molding txheej txheem, kev taw qhia cov nyhuv ntawm cov polymers raws cov dej ntws coj mus rau anisotropy hauv cov yas. Lub shrinkage ntawm ib feem yuav inevitably txawv nyob ntawm seb cov kev taw qhia ntawm cov khoom ntws: feem ntau, shrinkage yog ntau dua thiab lub zog yog siab dua nyob rau hauv cov ntaub ntawv khiav kev taw qhia, thaum shrinkage yog me me thiab lub zog yog qis dua nyob rau hauv cov kev taw qhia perpendicular mus rau cov khoom ntws. Nyob rau tib lub sijhawm, vim qhov tsis sib xws thiab qhov ntom ntom ntawm cov khoom siv ntxiv hauv ntau qhov sib txawv ntawm cov yas, shrinkage kuj tsis sib xws, ua rau qhov sib txawv shrinkage thiab ua rau cov yas feem ntau ua rau warping, deformation, thiab txawm tawg.
(2) Fluidity
Thaum lub sij hawm molding txheej txheem, lub peev xwm ntawm cov yas ntim cov pwm kab noj hniav nyob rau hauv tej yam kub thiab siab yog hu ua fluidity ntawm yas. Qhov no yog ib qho kev qhia tshwj xeeb qhia txog kev txhaj tshuaj molding. Thaum lub sij hawm molding, yuav tsum tau them nyiaj mloog mus rau qhov ntev ntawm cov pwm kab noj hniav thiab nws cov tsis muaj feem xyuam. Thaum lub molding siab loj dhau los yog me me, qhov cuam tshuam ntawm fluidity yuav tsum tau xav txog.
Qhov loj ntawm fluidity muaj kev sib raug zoo nrog cov qauv molecular ntawm plastics. Cov yas uas muaj cov qauv kab molecular los yog qhov hnyav dua molecular muaj qhov cuam tshuam tsawg rau cov dej molecular, ua rau muaj dej ntau dua. Thaum ntxiv cov fillers rau plastics, fluidity nce nrog cov ntsiab lus muab tub lim ntau dua. Kev cuam tshuam ntawm ntau yam tsim thiab molding txheej txheem ntawm cov yas fluidity kuj muaj feem xyuam rau cov fluidity ntawm polymer tebchaw.
Lub fluidity ntawm plastics tsis yog tus nqi tsis sib xws, thiab pwm tsim tuaj yeem kho nws mus rau qhov zoo. Yog hais tias lub fluidity ntawm plastics zoo, nws tsis tas txhais hais tias txhua yam ntawm cov txheej txheem txhaj tshuaj molding yog du thiab txaus siab. Hloov pauv, yog tias qhov fluidity tsis zoo, nws tuaj yeem txhim kho los ntawm kev nce qhov kev txhaj tshuaj molding kub lossis siab. Txawm li cas los xij, yog tias qhov fluidity zoo heev, nws tuaj yeem ua rau muaj qhov tsis xws luag xws li flash hauv kev tsim cov khoom yas. Yog li ntawd, nyob rau hauv cov txheej txheem molding, kev siv cov ntaub ntawv yas yuav tsum xav txog txhua yam ntawm kev cuam tshuam thiab kev xaiv cov khoom tsim nyog. Tsuas yog tom qab ntawd tuaj yeem ua tau zoo tuaj yeem lav thiab cov txheej txheem molding tsis thiab pwm tsim raug xaiv kom tsim nyog, thaum kawg ua tiav lub hom phiaj ntawm kev tswj thiab txhim kho kom zoo.
Raws li qhov fluidity ntawm cov khoom siv hauv pwm tsim, kev faib tawm fluidity ntawm thermoplastic txhaj molding feem ntau tuaj yeem muab faib ua peb pawg:
① Zoo fluidity plastics: xws li nylon, polyethylene, polypropylene, polystyrene, acrylic, cellulose acetate butyrate, thiab polyoxymethylene.
② Medium fluidity plastics: xws li hloov polystyrene, ABS, AS, polyformaldehyde, vinyl chloride homopolymer, thiab polytetrafluoroethylene.
③ Cov yas tsis muaj dej tsis zoo: xws li polycarbonate, tawv polyvinyl chloride, polysulfone, polyimide, polyester aromatic, thiab fluoroplastics.
Lub ntsiab tseem ceeb cuam tshuam rau qhov fluidity ntawm kev txhaj tshuaj molding yas yog:
① Yas kub. Thaum cov yas kub yog siab, qhov fluidity nce ntxiv nrog rau qhov kub ntawm cov yas sib txawv. Piv txwv li, polystyrene, polypropylene, polyamide, polyoxymethylene, hloov polystyrene, cellulose acetate, thiab ABS muaj rhiab heev kub dependence ntawm fluidity; rau polyvinyl chloride, polyformaldehyde, thiab polymethyl methacrylate, qhov cuam tshuam ntawm kub hloov ntawm fluidity yog me me.
② Txhaj siab. Kev txhaj tshuaj ntau ntxiv tuaj yeem kov yeej qhov kev tawm tsam uas tsim los ntawm cov yaj ntws, thiab sib txuas ua kom cov yaj sau nrawm, ua kom muaj dej ntau dua.
③ Pwm qauv. Xws li daim ntawv ntawm lub rooj vag, qhov chaw ntawm qhov rooj thiab qhov loj me, kab noj hniav, qhov tso pa tawm, pwm kub, phab ntsa tuab ntawm cov khoom yas, thiab muaj cov khoom ntxig, tus naj npawb thiab qhov chaw ntawm cov ntxig ntxig - tag nrho cov no ncaj qha cuam tshuam rau qhov tseeb ntim hauv pwm kab noj hniav thiab muaj feem cuam tshuam rau cov yas fluidity.
(3) Thaum tshav kub kub rhiab heev
Lub viscosity ntawm ib co plastics hloov nrog kub thaum lub sij hawm molding txheej txheem ntawm qis kub, thiab cov plastics tseem nyob ruaj khov. Txawm li cas los xij, thaum qhov kub thiab txias tau khaws cia ntawm qhov kub molding ntau dua rau lub sijhawm ntev, los yog tus ntoo khaub lig- ntu ntu ntawm qhov ntws ntws tsawg dhau, lossis tus nqi shear siab dhau lawm, phenomena xws li discoloration, degradation, thiab decomposition yuav tshwm sim vim qhov nce shear action. Cov yas uas muaj cov yam ntxwv no yog hu ua cua sov- cov yas rhiab heev. Xws li tawv PVC, polyvinyl chloride, polyformaldehyde, polyfluoroethylene, thiab fluoroplastics. Thaum tshav kub kub- cov plastics rhiab heev decompose thiab tso gases thaum lub sij hawm degradation, uas corrode pwm thiab cuam tshuam cov tsos ntawm cov yas seem. Ntxiv mus, lawv lub cev thiab mechanical zog kuj deteriorate.
Thaum tshav kub kub- cov plastics rhiab heev dhau los ntawm tshav kub-induced decomposition los yog degradation thaum lub sij hawm cua sov, ntau yam decomposition khoom yuav raug generated, ib co ntawm cov teeb meem rau tib neeg lub cev. Cov pwm thiab cov khoom siv yuav tsum tau ua kom huv si. Cov impurities los yog av yuav ua rau lub zos overheating thiab ua rau cov khoom degradation.
Cov neeg sawv cev thiab cov khoom siv ntxiv tuaj yeem tiv thaiv kev puas tsuaj ntxiv. Piv txwv li, ntxiv cov hluav taws kub stabilizers kom nruj PVC tuaj yeem txhim kho nws cov nyhuv decomposition.
Thaum tshav kub kub- cov yas rhiab heev yog molded nyob rau hauv tej yam kev mob uas ua hauj lwm yog overheated los yog decomposition tshwm sim, ib co kev ntsuas yuav tsum tau coj thaum lub sij hawm tsim pwm. Thaum tshav kub kub stabilizers tuaj yeem muab ntxiv rau cov khoom siv, lossis cov khoom siv tsim nyog (ntsia hlau- hom txhaj tshuaj) tuaj yeem siv. Kev tswj nruj yuav tsum tau tswj xyuas qhov kub ntawm molding, chim kub, lub sij hawm cua sov, ntsia hlau tig ceev thiab siab; thiab kev ntsuas xws li kev tiv thaiv cov khoom khaws cia thiab tiv thaiv cov cuab yeej thiab pwm los ntawm kev kis kab mob yuav tsum tau ua.
(4) Moisture Sensitivity
Cov dej rhiab heev ntawm cov yas yog hais txog qhov rhiab heev rau cov dej noo decomposition ntawm qhov kub thiab txias, xws li polycarbonate uas yog ib txwm ya raws - rhiab yas. Txawm hais tias nws muaj me me ntawm cov dej noo, nws yuav decompose ntawm qhov kub thiab txias. Yog li ntawd, noo noo- cov yas rhiab heev yuav tsum tau tswj nruj me ntsis rau cov ntsiab lus noo noo ua ntej molding thiab yuav tsum tau kho kom qhuav.
(5) Hygroscopicity
Hygroscopicity yog hais txog affinity ntawm plastics rau ya raws. Raws li qhov no, cov yas tuaj yeem muab faib ua ob pawg: ib qho yog cov yas nrog cov dej nqus dej lossis cov khoom adhesion, xws li polyamide, polycarbonate, polyester, ABS, thiab lwm yam.; Lwm qhov yog cov yas uas tsis nqus dej los yog ua raws li cov dej noo, xws li polystyrene, polypropylene, thiab polyethylene.
Rau cov yas nrog dej nqus dej, yog tias cov ntsiab lus noo noo ua ntej molding tsis raug tshem tawm thiab tshaj qhov txwv, ces thaum lub sij hawm molding txheej txheem, noo noo yuav hloov mus rau hauv cov roj thiab ua rau cov yas decompose, uas ua rau txo flowability ntawm molded yas, nyuaj molding, thiab deterioration ntawm nto zoo thiab mechanical zog ntawm cov yas qhov chaw. Yog li ntawd, txhawm rau xyuas kom meej qhov kev vam meej thiab zoo ntawm molding, rau cov yas nrog loj hygroscopicity thiab adhesion rau ya raws, noo noo yuav tsum tau muab tshem tawm ua ntej molding thiab qhuav kev kho mob yuav tsum tau ua. Kev saib xyuas kuj yuav tsum tau them rau qhov tsim nyog ntawm qhov kub thiab txias sab nraud ntawm lub tshuab txhaj tshuaj molding.
(6) Compatibility
Compatibility yog hais txog kev muaj peev xwm ntawm ob lossis ntau hom yas sib txawv kom tsis txhob raug kev sib cais hauv lub xeev molten.
Yog tias ob hom plastics tsis sib haum, kev sib cais theem yuav tshwm sim thaum lub sij hawm melting thiab molding txheej txheem, uas ua rau delamination, tev, thiab deformation ntawm qhov chaw. Lub incompatibility ntawm plastics muaj feem xyuam rau lawv cov qauv molecular. Cov qauv molecular uas zoo sib xws lossis yooj yim sib xws yog sib xws, xws li siab -siab polyethylene thiab qis-siab polyethylene, polypropylene sib xyaw; Cov qauv molecular uas tsis sib xws yog qhov nyuaj rau kev sib xyaw, xws li sib xyaw ntawm polyethylene thiab polystyrene. Lub compatibility ntawm plastics kuj feem ntau hu ua miscibility. Kev nkag siab txog cov yam ntxwv ntawm cov yas no tuaj yeem pab txiav txim siab qhov sib xws ntawm cov khoom zoo sib xws lossis cov khoom siv raw, uas yog ib txoj hauv kev tseem ceeb los txhim kho kev ua haujlwm ntawm cov yas.