Free radical polymerizations of some vinyl monomers in carbon dioxide fluid

Abstract

The effect of pressure ranging from ambient atmosphere to 28.5 MPa on the free radical polymerizations of methyl methacrylate (MMA) in carbon dioxide (CO 2 ) was investigated and discussed. The poly (methyl methacrylate) (PMMA) with high molecular weight was synthesized at quite high conversion of MMA in the polymerization at or below 9.2 MPa, as compared to those polymerized under 11.8-28.5 MPa. A phase transition behavior of MMA-CO 2 binary mixture from homogeneous state to vapor-liquid equilibrium (VLE) state was observed below 10.51 MPa. In such a VLE system, almost all MMA was found to exist in the liquid phase with higher concentration than that in homogenous system. Thus, the fast polymerization rate of MMA and high molecular weight of PMMA could be related to the VLE state of MMA/CO 2 under low pressure. Similar phenomena were also observed in the polymerization systems of styrene and vinyl acetate in CO 2 , respectively.

Mechanical and thermal properties of perfluoroalkyl ethyl methacrylate–methyl methacrylate statistical copolymers synthesized in supercritical carbon dioxide

“…Copolymerization was started in a homogenous scCO 2 medium, but when the conversion increased sufficiently in a short period of time, the copolymerization medium was changed into a heterogeneous system consisting of scCO 2 and liquid CO 2 , especially for the copolymerizations containing high MMA content. Thus, the increase in the Zonly-TM content in the feed resulted in the increase in the duration of the homogeneous polymerization in scCO 2 causing the decrease of the copolymer M w consistent with the literature [44].…”

“…Above this MMA content ratio, the copolymerization medium changed from homogenous to heterogeneous [43]. Wang et al indicated that vinyl monomer polymerization like MMA conversion and M w of the PMMA were increased at the pressure decreasing MMA-CO 2 mixture at vapor-liquid equilibrium pressure including CO 2 and MMA liquids and vapors [44]. They suggested that this phenomena was related to the presence of MMA monomer in the liquid CO 2 phase with higher concentration than that of the homogenous phase, so the polymerization rate in liquid CO 2 phase was faster than the homogenous phase [44].…”

“…Wang et al indicated that vinyl monomer polymerization like MMA conversion and M w of the PMMA were increased at the pressure decreasing MMA-CO 2 mixture at vapor-liquid equilibrium pressure including CO 2 and MMA liquids and vapors [44]. They suggested that this phenomena was related to the presence of MMA monomer in the liquid CO 2 phase with higher concentration than that of the homogenous phase, so the polymerization rate in liquid CO 2 phase was faster than the homogenous phase [44]. In our study, it is possible that the copolymerization occurs both in scCO 2 and liquid CO 2 phases due to low polymerization pressure of 130 bar.…”

Multiscale Simulation of Vinyl Acetate Systems Applied in the Industrial Gas Separation Column

“…However, it was found that the binary interaction parameters of C 2 H 2 , CO 2 , CH 3 CHO, and VAc in the thermodynamic models, such as UNIQUAC, NRTL, and Wilson, were missing in the modern modeling packages (such as PROII, Aspen, and ChemCAD). Although fitting binary VLE experimental data is the most accurate and feasible method to obtain binary interaction parameters, there are few experimental data about gas and VAC mixtures and also only a limited number of data about the CH 3 CHO-VAc system and C 2 H 2 -CO 2 were reported. − Meanwhile, because the VLE data of the VAC-C 2 H 2 system was difficult to measure, only the data from −15 to 20 °C were measured by Kizlink et al…”

Συστηματική Μελέτη Των Παραγόντων Που Επηρεάζουν Την Προστατευτική Ικανότητα Επιστρώσεων Σε Έργα Πολιτισμού

“…Η συµπεριφορά αυτά µπορεί να εξηγηθεί βάσει του γεγονότος ότι όσο αυξάνεται ο αριθµός των ατόµων φθορίου στην πολυµερική αλυσίδα, τόσο αυξάνεται και η δυσδιαλυτότητά τους Στο διάγραµµα που ακολουθεί φαίνεται η µεταβολή της πίεσης σε σχέση µε το χρόνο πολυµερισµού και προκύπτει ότι και στις δυο περιπτώσεις η τελική πίεση είναι µεγαλύτερη από την αρχική. Παρόµοια συµπεριφορά παρατηρείται σε αντίστοιχες µελέτες που αφορούν τον πολυµερισµό βινυλικών µονοµερών [Chatzidoukas, et al, 2003, Hsiao, et al, 1995, Kwon, et al, 2004, Lepilleur, et al, 1997, Wang, et al, 2008. Πιο συγκεκριµένα, προκύπτει ότι για αρχικές πιέσεις κάτω από περίπου 230 bar η τελική πίεση είναι µεγαλύτερη από την αρχική [Chatzidoukas, et al, 2003].…”