Polyvinyl Cawv (PVA) Cov Txheej Txheem Ntau Lawm thiab Kev Tswj Xyuas Zoo

Polyvinyl cawv (PVA) yog tsim los ntawm ob- cov txheej txheem: polymerization ntawm vinyl acetate los ua polyvinyl acetate (PVAc), ua raws li hydrolysis ntawm PVAc los hloov acetate pawg rau hydroxyl pawg. Cov txheej txheem tsim khoom thiab kev tswj xyuas tsis zoo ncaj qha txiav txim siab cov khoom thiab kev ua haujlwm ntawm PVA, ua rau lawv tseem ceeb rau cov tuam txhab, xa tawm, thiab cov neeg yuav khoom lag luam.

 

Thawj kauj ruam hauv PVA ntau lawm yog lub polymerization ntawm vinyl acetate. Qhov no feem ntau yog ua los ntawm emulsion polymerization, qhov twg vinyl acetate monomers tov nrog dej, emulsifiers, thiab cov pib (xws li peroxides) thiab rhuab mus rau 60-80 degree. Cov tshuaj tiv thaiv polymerization tsim PVAc emulsion, uas tom qab ntawd qhuav los ua PVAc cob. Qhov hnyav molecular ntawm PVAc, uas txiav txim siab qhov hnyav molecular ntawm cov khoom PVA kawg, yog tswj los ntawm kev kho qhov kub thiab txias, qhov pib concentration, thiab lub sijhawm tshuaj tiv thaiv.

 

Cov kauj ruam thib ob yog hydrolysis (alcoholysis) ntawm PVAc. PVAc yog reacted nrog methanol nyob rau hauv lub xub ntiag ntawm ib tug catalyst (xws li sodium hydroxide) los hloov acetate pawg (-OOCCH₃) rau hydroxyl pawg (-OH). Lub℃ntawm hydrolysis, uas nyob ntawm 87% mus rau 99%, yog tswj los ntawm kev kho cov catalyst concentration, tshuaj tiv thaiv kub, thiab cov tshuaj tiv thaiv lub sij hawm. Siab hydrolyzed PVA (98-99% hydrolysis) yuav tsum tau lub sij hawm ntev dua cov tshuaj tiv thaiv thiab siab dua catalyst concentration dua li ib nrab hydrolyzed PVA (87-89% hydrolysis).

 

Tom qab hydrolysis, PVA tov yog neutralized, lim, thiab qhuav los tsim PVA flakes lossis hmoov. Cov txheej txheem ziab yog qhov tseem ceeb rau kev tshem tawm cov dej noo thiab ua kom cov khoom ruaj khov; Cov dej noo ntau dhau tuaj yeem ua rau caking thiab txo cov solubility.

 

Cov kev tswj xyuas qhov tseem ceeb rau PVA suav nrog qib ntawm hydrolysis, qhov hnyav molecular, viscosity, purity, thiab noo noo cov ntsiab lus. Degree ntawm hydrolysis txiav txim siab solubility thiab dej tsis kam, thaum molecular hnyav cuam tshuam rau txhua yam muaj zog thiab zaj duab xis- tsim muaj peev xwm. Viscosity ( ntsuas hauv mPa·s) yog qhov taw qhia tseem ceeb ntawm qhov hnyav molecular, nrog cov viscosity siab dua qhia qhov hnyav dua molecular. Purity (Ntau dua lossis sib npaug li 98%) ua kom cov impurities tsawg, uas tuaj yeem cuam tshuam rau adhesion thiab zaj duab xis zoo. Cov ntsiab lus noo noo (tsawg dua lossis sib npaug li 5%) tiv thaiv caking thiab ua kom ntev - lub sijhawm cia ruaj khov.

 

Kev soj ntsuam zoo yog ua thoob plaws hauv cov txheej txheem tsim khoom, siv cov tswv yim xws li titration (los ntsuas qib ntawm hydrolysis), viscometry (los ntsuas viscosity), thiab siab -kev ua haujlwm ua kua chromatography (HPLC) (los ntsuas purity). Txhua pawg ntawm PVA yuav tsum tau nrog Daim Ntawv Pov Thawj Kev Ntsuam Xyuas (CoA) txheeb xyuas kev ua raws li cov qauv zoo.

 

Rau exporters thiab industrial buyers, nkag siab txog cov txheej txheem ntau lawm thiab kev tswj tsis zoo ntawmPolyvinyl cawv (PVA)pab xyuas kom lawv xaiv cov khoom zoo- ua tau raws li lawv daim ntawv thov. Los ntawm kev koom tes nrog cov tuam txhab lag luam nrog kev tswj hwm nruj, cov neeg yuav khoom tuaj yeem ua kom cov khoom lag luam zoo ib yam thiab zam kev tsim khoom qeeb los ntawm PVA tsis zoo.