Study of the polymerization of solid vinyl monomers using differential scanning calorimetry (original) (raw)
Frontal radical polymerization of vinyl monomers in non-stationary mode is investigated theoretically. It is shown that the formation and the time of establishment of steady-state polymerization heat autowaves considerably depend on the initial temperature, T i . When T i is less than the adiabatic heating temperature (T a ), the excess heat and relatively high conversion foster front formation before the non-stationary one. Whereas, for T i > T a , steady-state frontal polymerization regime is established, when the heat flow from the outer source is considerably less than the heat evolving due to the chemical reaction.
The Chemical Engineering Journal
Frontal radical polymerization of vinyl monomers in non-stationary mode is investigated theoretically. It is shown that the formation and the time of establishment of steady-state polymerization heat autowaves considerably depend on the initial temperature, T i . When T i is less than the adiabatic heating temperature (T a ), the excess heat and relatively high conversion foster front formation before the non-stationary one. Whereas, for T i > T a , steady-state frontal polymerization regime is established, when the heat flow from the outer source is considerably less than the heat evolving due to the chemical reaction.
Inter- and intra-molecular interactions in anionic polymerization of polar vinyl monomers
2014
This review article presents the results on the nature of the active centers of propagation (AC) in anionic polymerization of polar vinyl monomers such as acrylates, methacrylates, vinyl nitriles and vinyl ketones and especially their interactions with donor-acceptor ligands, carried out in the Laboratory of Polymerization Processes of the Institute of Polymers, Bulgarian Academy of Sciences. Particular attention to the interactions involving AC with lithium and magnesium counter-ions was paid due to their strong tendency of interacting with a variety of ligands, as well as in reactions of self-association resulting in numerous possibilities of controlling the structure of the polymers as well as the composition of copolymers. The model compounds or “living”oligomers of polar vinyl monomers were studied intensively by using IR spectroscopy and conductometry. Their physicochemical characteristics in solution, before and after adding of ligands, were investigated. A typical feature is...
Peculiarities of establishment of steady-state frontal polymerization of vinyl monomers
Chemical Engineering Journal, 2009
Frontal radical polymerization of vinyl monomers in non-stationary mode is investigated theoretically. It is shown that the formation and the time of establishment of steady-state polymerization heat autowaves considerably depend on the initial temperature, T i . When T i is less than the adiabatic heating temperature (T a ), the excess heat and relatively high conversion foster front formation before the non-stationary one. Whereas, for T i > T a , steady-state frontal polymerization regime is established, when the heat flow from the outer source is considerably less than the heat evolving due to the chemical reaction.
Cationic polymerization of vinyl monomers initiated by 10‐methylphenothiazine cation radicals
Journal of Polymer Science Part A: Polymer Chemistry, 1994
A small quantity of 10‐methylphenothiazine cation radical (MPT.+), electrochemically prepared and stocked in acetonitrile solution, initiated cationic polymerizations of n‐butyl, t‐butyl, and 2‐methoxyethyl vinyl ethers and p‐methoxystyrene, while no initiation occurred for phenyl vinyl ether, styrene, methyl methacrylate, and phenyl glycidyl ether. 1H‐NMR studies of oligomers and low molecular weight compounds isolated from the reaction mixture for the polymerization of t‐butyl vinyl ether in the presence of a small amount of D2O indicated that electron transfer from the monomer to MPT.+ was involved in the initiation step. 1H‐ and 13C‐NMR and MO calculation implied that monomers with higher electron densities on the vinyl groups and with lower ionization potentials were more susceptible to the initiation of MPT.+. © 1994 John Wiley & Sons, Inc.
Influence of thermal initiation on the radical polymerization of unsaturated monomers
Journal of Polymer Science Part A: Polymer Chemistry, 1989
The effect of thermal initiation of the radical polymerization of unsaturated monomem has been analyzed by considering a kinetic scheme that includes thermal: and catalyst-induced formation of free radicals, propagation, and termination reactions. Expressions relating the different rate constants with the instantaneous monomer concentration are derived and they indicate the great influence of thermal initiation on the kinetic results. Application to a real case suggests that evaluation of k , and k , / k~/ 2 from experimental results using the method of dead-end polymerization may lead to erroneous values of these constants.
Solvation effects in anionic polymerization of polar vinyl monomers
Die makromolekulare Chemie, 1992
The anionic polymerization ( A p ) of polar vinyl monomers ( M I is strongly affected by additives with electron donor and electron acceptor properties. For the purpose of estimating the interactions of the active centers (AC) of chain growth with different ligands, the appraach o i studying a reference system was adopted, viz. lithium picrate (LiPi) in dioxane (DO). Three types of interaction were distinguished: with electron pair donors (EPD), with Li salts and alkoxides, and with Lewis acids. Spectral evidence was f w n d o+ charge transfer complexation with Li alkoxides and enolates. leading to modified dianionic Meisenheimer adductc. The experimental procedure was employed in studies of competitive solvation of LiPi by two ligandr. The results were related to reviewed literature data on the kinetics and stereochemistry of methyl nethacrylate (MMA) and 2-vinylpyridine (ZVP) polymerizations by 1 ithium initiators. Ever since the discovery of "living" AP, there has been much interest in M which proved to be a true challenge to the researcher. In contrast to the "clean" polymerization conditions easily provided in the case of non-polar hydrocarbon monumers, reaction systems involving polar vinyl and cyclic monomers are intrinsically much more complex due to the r o l e of one or more heteroatoms in their molecule. On the other hand, the presence of this heteroatom allows a better control on the reaction mechanism giving rise to possibilities o f , for instance, stereoregulation. For this reason. orgrnolithiun initiators have been most extensively studied (Ref.1) the counterion in this case being the strongest Lewis acid w n g a]. kal i metal cations. In W M polymerization the nucleophile is usually an ambident anion (Ah). m e heteroatom on the charged end of the growing chain contributes to considerable localization of the negative charge and substantially increases the electrostatic interaction in the ion pair. The small size of Li a l s o leads
A calorimetric study of the self-polymerization of a commercial monomer: An incident investigation
2011
In this work the analysis of an incident in transport of dangerous goods is proposed. The objective of this study is to contribute to the determination of the causes that brought about the self-polymerization of commercial divinylbenzene (DVB 63%) contained in an isothermal container, in order to prevent this incident from happening in the future. Time and conditions during transport/storage of monomers (in particular storage temperature) are very important factors that affect their aptitude of self-polymerization. In particular one hypothesis has been investigated: that the quantity of oxygen in the tanker was insufficient to activate properly the inhibition mechanism. Consequently, the self-polymerization of DVB and the inhibition mechanism of 4-tert-Butylcatechol (TBC) have been studied as a function of temperature and monomer exposure to air with Differential Scanning Calorimetry and Adiabatic Calorimetry techniques.
Effect of UV-curing conditions on the cationic polymerization kinetics of vinyl ether monomers
International Journal of Scientific Research in Science, Engineering and Technology, 2022
In this study, the performance of a new triarylsulfonium photoinitiator in the initiation of cationic polymerization of vinyl monomers was investigated by infrared spectroscopy (IR). The effect of the emission spectrum of light sources on the kinetics of the curing process was examined. The results indicate that the light source characterized by a total overlap of its emission spectrum with the photoinitiator absorption spectrum is the best system for effective cure. In the case of smaller overlap of spectrums, the conversion degree and the rate are lower. Nevertheless, it is easy to regulate by extending the energy of the emitted light. At the UVB light source, the maximal conversion degree is 71.8%, with the polymerization rate of 1.68 s-1, which is faster than the corresponding free-radical photopolymerization of acrylic monomers.
Effect of Cationic Photoinitiator on the Polymerization Kinetics of Vinyl Ether Monomers
In this study, the performance of a new triarylsulfonium photoinitiators in the initiation of cationic polymerization of vinyl monomers was investigated by infrared spectroscopy (IR). The photoinitiator exhibit absorption characteristics compatible with the emission characteristics of medium pressure mercury lamps, which are the main sources of UV light in the industry. The experimental results indicate that the photoinitiator is most effective at a concentration of 1%. At the investigated conditions, the maximal conversion degree is 77.8% and the polymerization rate is 0.56 s -1 . The curing process is even faster than the corresponding free-radical photopolymerization of acrylic monomers
Radical polymerization of methyl trans-β-vinylacrylate
Journal of Polymer Science Part A: Polymer Chemistry, 1995
Methyl trans-P-vinylacrylate (MVA) undergoes radical polymerization with a,a'-azobis(isobutyronitri1e) (AIBN) in bulk and solution. The polymer obtained consists of 85% trans-l,4 and 15% truns-3,4 units. Poly(MVA) (PMVA) is readily soluble in common organic solvents, but insoluble in n-hexane and petroleum ether. PMVA exhibits a glass transition at 6"C, and loses no weight up to 300°C in nitrogen. The kinetics of MVA homopolymerization with AIBN was investigated in benzene. The rate of polymerization (R,) can be expressed by R,, = k[AIBN]o.5[MVA]'.o, and the overall activation energy has been calculated to be 94 kJ/mol. The propagation radical of MVA at 80°C was detected by ESR spectroscopy, which indicated that the unpaired electron of the propagating radical was completely delocalized over the three ally1 carbons. Furthermore, the steady-state concentration of the propagating radical of MVA a t 60°C was determined by ESR spectroscopy, and the propagation rate constant (kp) was calculated to be 1.25 X 10' L/mol.s. Monomer reactivity ratios in copolymerization of MVA (M 2) with styrene (M ,) are r1 = 0.16 and r2 = 4.9, from which Q and e values of MVA are calculated as 4.2 and-0.32, respectively.
Macromolecules, 1987
The oligomerization and polymerization of racemic and highly optically enriched vinyl phenyl sulfoxide (3) were carried out in THF at-78 "C. Dimer and trimer stereochemistry was consistent with the stereospecific addition of 3 to an ion pair epimer of 1-lithio(phenylsulfiny1)ethane (2) or l-lithio-1,3-bis-(phenylsulfiny1)butane (4), where the stereoelectivity for one enantiomer of 3 over the other was large. The polymerization of racemic 3 resulted in the formation of an apparently atactic polymer. In contrast, the polymerization of highly optically enriched 3 resulted in the formation of an apparently highly stereoregular polymer. These results are shown to be consistent with a process where many chain-end epimers may participate in the polymerization and each epimer undergoes vinyl addition stereospecifically and stereoelectively. However, the formation of a stereoregular polymer from optically active monomer requires that the chirality of the ion pair influence the stereoelectivity.
Polymerization of dialkyl fumarates by differential scanning calorimetry
Polymer Testing, 2001
The solid-state polymerization of several dialkyl fumarates (DAF) containing different side groups have been investigated using differential scanning calorimetry (DSC). Four free radical initiators were tested with seven DAF derivatives. The type of initiator was found to have a pronounced effect on the polymerization behavior. Polymerization was confirmed mainly using NMR spectroscopy on the extracted polymers from the DSC pans. The activation energy as well as the order of the polymerization reaction for each of the investigated DAF was measured using the Ozawa method. It has been shown that DSC is an easy and versatile way to follow the kinetic of the free radical polymerization of solid monomers.
Journal of Applied Polymer Science, 2003
The solid-state radical polymerization of sodium methacrylate was investigated. It was initiated by azobisisobutyronitrile, which was used as a radical initiator. Differential scanning calorimetry (DSC) was used to observe the endothermic and exothermic transitions during the polymerization reaction. Structural studies were performed with the DSC thermograms and Fourier transform infrared and ultraviolet-visible spectra, and all of the results confirmed the progress of the reaction. The obtained data revealed that the polymerization reaction proceeded completely with a 100% conversion. ⌬H of this reaction was calculated with various amounts of the initiator, and the peak temperatures were determined at different heating rates. The activation energy (19.7 kcal mol Ϫ1) was also obtained by the Kissinger method for this type of solid polymerization reaction.
Journal of Polymer Science Part A-polymer Chemistry, 1999
Free-radical polymerization of vinyl esters including vinyl propionate (VPr), vinyl isobutylate (ViBu), vinyl 2,2-dimethylbutylate (VDMB), vinyl 2,2-dimethylvalerate (VDMV), vinyl 2,2-bis(trifluoromethyl)propionate (VF6Pi), and vinyl benzoate (VBz) was carried out using fluoroalcohols as solvents, and the tacticity of the obtained polymers was determined by NMR analysis of the produced poly(vinyl alcohol) (PVA). The polymerization of VPr, ViBu, VDMB, and VDMV, which are bulkier than VAc, in fluoroalcohols afforded polymers rich in heterotacticity (up to mr ϭ 61%) similar to that of vinyl pivalate (VPi) whereas VAc is known to give a syndiotactic polymer under the reaction conditions used here. The polymerization of VF6Pi, which is the bulkiest among the monomers used in this study, gave a polymer rich in syndiotacticity in bulk and in fluoroalcohols regardless of the structure of the solvents. On the other hand, the polymerization of VBz in fluoroalcohols gave polymers with a higher isotacticity (up to mm ϭ 33%) than bulk polymerization. Thus the monomer structure strongly affected the stereochemistry of the free-radical polymerization of vinyl esters in fluoroalcohols.
Virtual Free-Radical Polymerization of Vinyl Monomers in View of Digital Twins
Polymers
The first case of virtual polymerization based on the concept of digital twins (DTs) is presented. The free-radical polymerization of vinyl monomers is considered to be a chain reaction consisting of a set of elementary ones. Those three types, related to the polymerization initiation and propagation as well as to the termination of polymer chain growth, are discussed. Special sets of DTs, whose total number approaches 60, distinguish each reaction type. The calculations are carried out using a semi-empirical version of the unrestricted Hartree–Fock approximation. The main energy and spin-density parameters of the ground state of the DTs are determined. The barrier profiles of two pairs of DTs are calculated, based on which two Evans–Polanyi–Semenov relations, attributed to elementary reactions of type (1) and (2), are constructed. These provide a quite reliable evaluation of the activation energy for the initiation and propagation of the free-radical polymerization of vinyl monomer...
Photo-differential scanning calorimetry studies of cationic polymerizations of divinyl ethers
Polymer, 1995
Photo-differential scanning calorimetry experiments were used to determine effective kinetic constants for propagation and termination for a series of unsteady-state divinyl ether polymerizations at different temperatures and light intensities. For these cationic photopolymerizations the reaction rate and limiting conversion were both found to increase as the reaction temperature was increased. At all temperatures the profile for the propagation rate constant &, exhibited a dramatic increase at the start of the reaction, plateaued at a value between 5 and 30 1 mol -' s-l (depending upon temperature) and then decreased as the reaction reached a limiting conversion owing to trapping of the active centres. The effective termination rate constant k, was very low, with active centre lifetimes approaching 20 min. The overall activation energy for polymerization was found to be 26.5 & 3.2 kJ mol-' (