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Yog li cas polyvinyl alcohol yog cov ntaub ntawv tseem ceeb rau cov biodegradable films
OECD 301 standards thiab kev ua haujlwm ntawm biodegradation nyob rau hauv qhov kev xav tau ntawm polyvinyl alcohol
Polyvinyl alcohol lossis PVA yog qhov muaj kev tawg tawm zoo heev thaum siv cov kws tshuaj xyuas OECD 301 los xyuas. Cov kws tshuaj xyuas no yog rau hais tias nws sim raws li yuav dhau nyob rau hauv dej thiab qhov chaw uas muaj microbe. Thaum siv cov kws tshuaj xyuas no, PVA films tawg tawm mus rau hauv cov khoob tshuaj ntau dua 60% tom qab 28 hnub, uas txhawb nqa thiab tshwj xeeb dua qhov tshwj xeeb tshaj plaws uas ISO 14851 thiab EN 13432 tau qhia tias yuav tsum muaj rau qhov tshwj xeeb uas yuav tsum tawg tawm zoo heev. Peb tau pom qhov no ua haujlwm nyob ntawd lub tsev kws tshuaj xyuas los. Cov chaw tshuaj xyuas dej tshuaj nyob rau hauv lub tsev muaj kev pab tshuaj xyuas (municipal wastewater treatment facilities) tau qhia tias PVA tawg tawm ntau dua 5.5 zaug ntau dua cov lus tshuaj uas muaj hauv tshuaj nyob rau hauv tshuaj nyob rau hauv tshuaj nyob rau hauv tshuaj nyob rau hauv tshuaj nyob rau hauv tshuaj nyob rau hauv tshuaj nyob rau hauv tshuaj nyob rau hauv tshuaj nyob rau hauv tshuaj nyob rau hauv tshuaj nyob rau hauv tshuaj nyob rau hauv tshuaj nyob rau hauv tshuaj nyob rau hauv tshuaj nyob rau hauv tshuaj nyob rau hauv tshuaj nyob rau hauv tshuaj nyob rau hauv tshuaj nyob rau hauv tshuaj nyob rau hauv tshuaj nyob rau hauv tshuaj nyob rau hauv tshuaj nyob rau hauv tshuaj nyob rau hauv tshuaj nyob rau hauv tshuaj nyob rau hauv tshuaj nyob rau hauv tshuaj nyob rau hauv tshuaj nyob rau hauv tshuaj nyob rau hauv tshuaj nyob rau hauv tshuaj nyob rau hauv tshuaj nyob rau hauv tshuaj nyob rau hauv tshuaj nyob rau hauv tshuaj nyob rau hauv tshuaj nyob rau hauv tshuaj nyob rau hauv tshuaj nyob rau hauv tshuaj nyob rau hauv tshuaj nyob rau hauv tshuaj nyob rau hauv tshuaj nyob rau hauv tshuaj nyob rau hauv tshuaj nyob rau hauv tshuaj nyob rau hauv tshuaj......
Yam li cas uas lub hauv paus ntawm cov khoom sib tw thiab qhov ntau ntau ntawm kev tshem tawm cov khoom sib tw yuav tshem tawm polyvinyl alcohol
PVA's kev tshem tawm yog qhov tshaj xws li muaj kev txhawb nqa rau ob qhov tswv yim ntawm qhov chaw: lub hauv paus ntawm cov khoom sib tw (MW) thiab qhov ntau ntau ntawm kev tshem tawm (DH). Cov lej no pab ua kom muaj kev suav nrog zoo rau qhov kev tshem tawm thiab qhov kev tshem tawm zoo tshaj plaws:
- Lub hauv paus ntawm cov khoom sib tw tsawg (10,000–30,000 Da) : Pab ua kom tshem tawm tau txhua yam rau hauv qhov chaw nyob rau hauv dej thaj tsam nyob rau hauv dej 15 hnub
- Kev tshem tawm ntau (ntau dua 98%) : Tsis pub rau kev tshem tawm thaum kawg, tab sis pab ua kom tshem tawm zoo dua—txog 89% ntawm kev tshem tawm rau hauv dej thiab 72% rau cov khoom uas tshem tawm tsawg dua
- Qhov tswv yim zoo tshaj plaws ntawm kev ua haujlwm : Cov phaj uas muaj kev tshem tawm 87–89% thiab lub hauv paus ntawm cov khoom sib tw zoo (nyob rau ~50,000 Da) yuav muaj kev nyab xeeb rau hauv 30 hnub kham mus li kev tshem tawm ntau dua thiab tshem tawm tau txhua yam
Qhov tu ntsib no ua rau PVA muaj qhlo kev siv tshwj tsis yog los ntawm kev siv detergent ib zaug uas xav tau kev siv tom qab ib feeb mus rau agricultural mulch films uas tsim los rau kev kuaj xyuas kev sib twb hauv ib co hlis.
Txhim kho Polyvinyl Alcohol Film Formulation rau kev pab thiab kev sau ceeb
Sau polyvinyl alcohol nrog starch thiab plasticizers los txhim kho kev tswj kom meej thiab kev sau ceeb
Thaum peb sib pua PVA nrog rau cov khoom tsim los ntawm lub neej xwb li starch thiab cov khoom siv los txav taws li glycerol, nws pab peb hloov pauv qhov tshwm sim ntawm cov khoom rau hauv dej, qhov zoo siab thiab qhov chaw tawm rau ib txhim khoob khoom, thaum koj tsis txhob muab nws mus rau qhov chaw siv. Muab ib feem ntawm 10 mus 20% ntawm starch tseem tuaj yeem ua rau cov khoom tsis tau sib sau rau hauv dej, uas txhais tau tias nws yuav nyiaj xyoo 40 mus 60% ntau tshaj los sib sau thaum nyob rau hauv dej. Ntawm no yog li cas nyob rau hauv kev ua haujlwm vim tias starch tso cai rau muaj cov kab ncaj ncees zoo dua rau oxygen, txo qhov txaus siab los ntawm li 25% vim tias muaj cov hydrogen bonds nyob saum starch thiab PVA. Qhov no yog qhov tseem ceeb rau cov khoom siv khub li sib ntxhuam, uas peb xav kom txo kom tsis txhob muaj cheeb. Tom qab ntawd, muab ib feem ntawm 5 mus 15% ntawm glycerol tuaj yeem ua rau cov film zoo dua thiab yooj yim dua rau siv hauv kev tsim khoom. Kev xam pom tias ib feem ntawm 10% glycerol tuaj yeem nce qhov tshwm sim ntawm tensile strength los ntawm 30% tsis txhob muab nws mus rau qhov chaw siv.
Tsim cov kev sib tw ntawm qhov loj hauv kev ua haujlwm thiab qhov tshuaj no tshuaj ntsuag rau hauv dej los ntawm kev xaiv cov yam ntxwv ntawm polyvinyl alcohol
Kuam ntxawv ntawm qhov loj hauv PVA thiab qhov nws tawg los yog ib qho uas tsis tuaj yeem txhawb rau li cas, thiab nws yog qhov tseem ceeb heev rau kev xaiv cov PVA uas muaj qhov zoo. Cov PVA uas muaj qhov loj hauv (ntawm 130k rau 186k g/mol) yog tseem ceeb rau kev tswj qhov tawg, thiab lawv yuav tawg thaum muaj kev puas ntsuas ntau dua 18 MPa. Tiamsi, cov PVA no yuav tawg ntau dua thaum muaj dej. Ntawd li, cov PVA uas muaj qhov hydrolysis 87-89% yuav tawg tau ntau dua peb zaug ntau dua cov PVA uas muaj qhov hydrolysis 98% los sis. Qhov no ua rau lawv yuav tswj tau qhov kev hloov hauv qhov chaw uas lawv nyob. Thaum cov neeg tsim khoom siv cov PVA los ua khoom ua hauv kev crosslinking nrog cov acid organic xwb li oxalic acid, lawv yuav tau qhov zoo dua. Thaum muaj 10% concentration, qhov kev siv no yuav ua rau qhov dej tshuab tau ntau dua ntau dua 50% thiab qhov tensile strength yuav ntau dua ntau dua 20%. Qhov no txhais tau dab tsi? Cov films yuav nyob zoo thaum siv nyob hauv kev siv tshwj xeeb, thiab yuav tawg tau txhua yam rau hauv dej ntawv (seawater) thaum muaj peb hnub, thiab qhov no yog qhov tseem ceeb rau ntau yam khoom.
Kev Tuag Tsom Ntau ntawm Polyvinyl Alcohol Films: Kev Xaiv Daim Pib Thiab Qhov Yeej Ua Tau
Solution casting vs. melt extrusion: feasibility, throughput, and thermal stability constraints for polyvinyl alcohol
Kwv yuav PVA films nrog qhov loj meej yog tias xws li sib phim lub tswvyim uas tsim nyog rau qhov keeb kwm ntawm cov khoom thiab qhov nws xav tau los ua haujlwm rau hauv cov khoom tiav. Lub tswvyim ua solution casting yog los sau PVA rau hauv dej tom qab ntawd txhim du dej saum 100 degrees Celsius. Lub tswvyim no pab tswj cov chawj polymer kom zoo ib daim thiab tsim cov films uas muaj zaj tas zoo tshaib, nyob rau hauv kev siv rau kho mob lossis rau kev siv uas xav tau kev tsham kub zoo tshaib. Tab sis muaj ib qho tseem ceeb: lub tswvyim no tsuas yog tuaj yeem ua tau txog ib tug neeg 5 kilograms saum ib teev vim tias dej nyuam qhuav ntev heev thiab qhov kev txhim du nyuj siab heev. Melt extrusion muab qhov ntau dua li 50 kg saum ib teev tab sis tsim nyog rau qhov kub ntawm 160 mus 200 degrees Celsius, uas tso PVA nyob deb nrawm rau qhov kub tshwm sim. Thaum kub tshaj 180 degrees, cov chawj polymer yuav qhua raug rau, cuam tshuam qhov siab ntawm 15% mus 30% thiab tsim cov film tsis zoo. Kev tswj kub zoo ib yam rau sab nraud ntawm plus or minus 5 degrees yog qhov tseem ceeb heev los tiv thaiv kev kaws tag thiab tswj cov molecular weight zoo. Tam sim no solution casting tsis tau tshwm sim rau qhov chaw muaj feem ntau, tab sis ntau qhov chaw tsim khoom siv rau cov khoom tsha tshiab biodegradable feem ntau siv melt extrusion, tshwj tsis yog thaum ntxiv nrog co-extrusion methods uas ntxiv cov layers tiv dej rau sab nraud ntawm PVA core los pab tiv thaiv nws hauv qab kev tsim khoom.
FAQ
Polyvinyl cawv yog dab tsi?
Polyvinyl alcohol (PVA) yog qhov polymer tshiab uas muaj peb yam ntxiv rau kev tawm ntawm cov ntaub ntawv thiab siv dav rau cov kev siv los ntawm kev kho cov ntaub ntawv thiab cov ntaub ntawv.
Puas yog polyvinyl alcohol ua qhov tshuaj tseem ceeb rau cov ntaub ntawv tawm ntawm cov ntaub ntawv?
PVA yog qhov tshuaj tseem ceeb vim nws muaj kev tawm ntawm cov ntaub ntawv zoo heev, uas tau pom los ntawm kev ua haujlwm hauv lub tsev thiab hauv kev siv nyob ze rau qhov txo ntawm kev siv, thiab nws muaj kev tswj hwm rau kev siv cov ntaub ntawv los ntawm kev tswj hwm cov ntaub ntawv.
Polyvinyl alcohol tawm ntawm cov ntaub ntawv li cas?
Cov ntaub ntawv PVA tawm ntawm cov ntaub ntawv los ntawm kev ua haujlwm ntawm cov ntaub ntawv, thiab cov xwm txheej ntawm qhov chaw siv yog qhov pab rau kev tawm ntawm cov ntaub ntawv. Cov qhov tshuaj uas muaj kev tswj hwm rau kev tawm ntawm cov ntaub ntawv yog cov ntaub ntawv thiab cov ntaub ntawv.