Cov khoom siv ntawm Pvc

PVC yas muaj cov duab sib txawv thiab kev ua haujlwm, suav nrog kev nias, extrusion, txhaj tshuaj thiab txheej. Qhov loj me me, ntses qhov muag, qhov ntom ntom, purity, txawv teb chaws impurities thiab porosity ntawm PVC resin tag nrho cuam tshuam rau kev ua haujlwm; Rau paste resin, viscosity thiab gelling khoom ntawm paste yuav tsum raug xam tias yog.
PVC yog amorphous polymer nrog me me shrinkage. Cov hmoov yuav tsum tau preheated ua ntej ua kom tshem tawm cov dej noo, txhim khu cov nyhuv plasticizing thiab tiv thaiv npuas. Ntxiv mus, PVC yog yooj yim heev rau decompose, tshwj xeeb tshaj yog nyob rau hauv kev sib cuag nrog hlau thiab tooj liab ntawm kub kub (decomposition kub 200 degree). Kev tsim kub ntau yog me me, thiab cov khoom siv kub yuav tsum tau tswj nruj me ntsis. Thaum siv cov ntsia hlau txhaj tshuaj thiab lub taub hau ncaj, lub qhov taub yuav tsum loj los tiv thaiv cov khoom stagnation hauv lub kaum sab xis tuag. Lub pwm pouring system yuav tsum loj, lub rooj vag seem yuav tsum loj, thiab cov pwm yuav tsum tau txias, pwm kub ntawm 30-60 degree thiab cov khoom kub ntawm 160-190 degree.
Nyob rau hauv lub iav hloov kub (Tg, 80 degree), PVC yog nyob rau hauv iav lub xeev; Ntawm Tg → viscous ntws kub (Tf, txog 160 degree), nws yog cov roj hmab elastic thiab yas; Ntawm Tf → thermal decomposition kub (Td), qhov ntws yog khov. Qhov kub siab dua, qhov yooj yim dua qhov ntws. Thaum qhov kub siab tshaj Td, PVC decomposes mus rau hauv ib tug loj npaum li cas ntawm hydrogen chloride (HCl), thiab cov khoom poob nws cov tshuaj stability thiab lub cev muaj zog zog. Yog li ntawd, Td yog lub siab txwv kub rau kev ua thiab molding. Vim yog lub zog loj ntawm polyethylene, Tf yog siab heev, txawm tias ze rau qhov kub decomposition, yog li cov yas yuav tsum tau ntxiv los txo Tf. Ntawm qhov tod tes, nws tseem yuav tsum tau ntxiv stabilizer, txhawm rau txhim kho Td ntawm PVC rau kev ua thiab molding.
Cov iav hloov pauv kub (Tg) tsuas yog cuam tshuam nrog cov saw ntu qauv ntawm cov saw hlau molecular, thiab muaj kev sib raug zoo me me nrog qhov hnyav molecular. Lub viscous flow kub (Tf) yog qhov kub ntawm qhov macromolecule pib txav, thiab muaj feem xyuam rau qhov hnyav molecular. Qhov loj dua qhov hnyav molecular, qhov siab dua Tf. Yog li ntawd, rau qee qhov kev txhaj tshuaj molding (xws li txhaj tshuaj molding), nws yog ib qho tsim nyog los txo qhov hnyav molecular ntawm resin. Raws li qhov sib txawv molecular hnyav, domestic suspension PVC resins muab faib ua 1-7 qib. Qhov loj dua tus naj npawb, qhov me me ntawm qhov hnyav molecular. XJ-4 (XS-4) rau XJ-7 (XS-7. PVC nrog qhov nruab nrab degree ntawm polymerization hauv qab 1000 yog hu ua qis degree ntawm polymerization PVC, uas muaj cov txheej txheem zoo Plasticizer tuaj yeem ntxiv tsawg dua thaum lub sijhawm ua haujlwm, kom cov khoom yuav tsis nrawm dua vim kev tsiv teb tsaws ntawm plasticizer. Tsawg polymerization degree PVC cov khoom muaj pob tshab zoo, thiab tau siv dav hauv cov khoom siv hauv tsev, khoom noj khoom haus thiab tshuaj ntim khoom, nrog rau los hloov cov khoom plexiglass.
Polyvinyl chloride yaj belongs rau non Newtonian pseudofluid. Qhov siab dua qhov shear ceev yog, qhov me dua qhov pom tseeb viscosity yog, thiab qhov kev hloov pauv yog qhov rhiab heev. Thaum qhov kub thiab txias nce, viscosity yuav tsis txo ntau. Txawm hais tias cov yas qis dua qhov kub ntawm qhov decomposition, nws tseem yuav ua kom sov thiab degraded vim oxidation, uas yuav cuam tshuam rau nws cov kev ua tau zoo. Yog li ntawd, nce tus nqi shear (nce lub siab) yuav tsum tau txiav txim siab los txhim kho lub fluidity ntawm PVC yaj. Qhov tseeb, ua kom lub zog sab nraud yog qhov tsim nyog rau kev txav ntawm macromolecules, kom Tf txo qis thiab macromolecules tuaj yeem ntws ntawm qhov kub thiab txias.