Ib qho ntawm cov thev naus laus zis tseem ceeb hauv kev tsim cov polycarbonate diols yog kev tswj hwm qhov hnyav molecular thiab molecular hnyav faib. Qhov hnyav molecular ntawm polycarbonate diols ncaj qha cuam tshuam lawv cov nqi hydroxyl, viscosity, thiab cov khoom ntawm cov khoom siv polyurethane. Thaum lub sij hawm synthesis, qhov piv ntawm diol rau carbonate raw cov ntaub ntawv yuav tsum tau ua tib zoo tswj, nrog rau cov tsis xws li cov tshuaj tiv thaiv kub, ntev, thiab siab, los xyuas kom meej cov tshuaj tiv thaiv mus rau qhov xav tau. Qhov sib txawv tseem ceeb hauv cov khoom siv raw cov khoom sib piv lossis kev tswj tsis raug ntawm cov tshuaj tiv thaiv tuaj yeem ua rau muaj kev hloov pauv hauv cov khoom lag luam molecular hnyav, yog li cuam tshuam rau kev suav cov qauv thiab cov khoom ua tau zoo thaum lub sijhawm polyurethane synthesis. Yog li ntawd, kev ntsuas qhov tseeb ntawm cov khoom siv raw thiab kev tswj cov txheej txheem tshuaj tiv thaiv yog qhov tseem ceeb rau kev ua kom cov khoom ruaj khov.
Kev xaiv thiab siv cov catalysts kuj yog ib qho tseem ceeb ntawm polycarbonate diol synthesis. Catalysts pab txhawb cov transesterification cov tshuaj tiv thaiv ntawm diols thiab carbonates, ceev cov tshuaj tiv thaiv, thiab cuam tshuam cov qauv molecular ntawm cov khoom kawg. Tsis txaus catalyst ntau npaum li cas ua rau qeeb cov tshuaj tiv thaiv thiab ncua sij hawm ntau lawm, whereas ntau npaum li cas yuav ua rau muaj kev cuam tshuam sab thiab nyuaj rau downstream khoom ua. Yog li ntawd, xaiv qhov tsim nyog catalyst raws li hom raw khoom thiab cov txheej txheem txheej txheem - thiab nruj me ntsis tswj qhov ntau npaum li cas - yog qhov tseem ceeb. Tsis tas li ntawd, residual catalyst tuaj yeem cuam tshuam cov tshuaj tiv thaiv polyurethane tom qab thiab cov khoom tsis kam rau yellowing; Yog li, kev tswj cov catalyst residues kuj yog ib qho tseem ceeb heev.
Kev tshem tawm raws sij hawm los ntawm- cov khoom lag luam thiab kev ua kom huv ntawm cov khoom kuj yog qhov tseem ceeb cuam tshuam rau qhov zoo ntawm polycarbonate diols. Tsawg-molecular- cov khoom hnyav, xws li methanol, yog tsim thaum lub sij hawm transesterification thiab polycondensation; tsis ua kom tshem tawm lawv tam sim ntawd los ntawm cov tshuaj tiv thaiv kab mob tuaj yeem cuam tshuam qhov kev loj hlob ntawm polymerization. Hauv kev tsim khoom, cov tshuaj tiv thaiv feem ntau yog tsav mus rau pem hauv ntej los ntawm kev nce qhov kub thiab txias, txo qhov siab, thiab tsis tu ncua tshem tawm cov khoom tsis zoo. Txawm li cas los xij, lub tshuab nqus tsev thiab cov khoom siv kub yuav tsum tau ua tib zoo tswj kom tsis txhob muaj cov khoom degradation los ntawm kev ua haujlwm hnyav dhau. Tom qab ua tiav cov tshuaj tiv thaiv, cov khoom tau txais kev kho mob xws li tshem tawm cov seem me me molecules thiab pom. Tsis tas li ntawd, cov ntsuas tsis suav nrog tus nqi hydroxyl, tus nqi kua qaub, cov ntsiab lus noo noo, viscosity, thiab xim raug kuaj kom ntseeg tau tias cov khoom zoo sib xws.