Factors affecting propagating fronts of addition polymerization: Velocity, front curvature, temperatue profile, conversion, and molecular weight distribution

Abstract

Several properties of propagating fronts of addition polymerization were studied. A power function could be fit to the velocity dependence on initiator concentration, but not with the exponents predicted by current models or in agreement with other published work. Bubbles from the volatile by‐products of initiator decomposition were found to affect the front velocity and curvature. The front velocity for triethylene glycol dimethacrylate polymerization was found to depend linearly on temperature over a moderate range. The conversion of methacrylic acid in fronts varied greatly with initiator type and concentration. Benzoyl peroxide produced much lower conversion than t‐butyl peroxide, but fronts with tBPO propagated slower. A dual initiator system of BPO and tBPO produced rapidly propagating fronts with good conversion but the contribution of each initiator to the velocity was not additive. The possibility of chain branching was considered. The apparent molecular weight distributions were very broad, often trimodal, and found to depend on initiator type and concentration as well as the tube diameter. The temperature profiles were measured and found to be very sharp for BPO and broader for tBPO but both had front temperatures in excess of 200°C, indicating a high ceiling temperature. © 1995 John Wiley & Sons, Inc.

Polymer blends by self-propagating frontal polymerization

“…) is lower than that measured under similar conditions, but with the monomer MAA alone (ϳ 0.8 cm min Ϫ1 ) 8,10 (i.e., without diluting it with PMMA).…”

“…As described in the Introduction, several works appeared in the literature dealing with different characteristics of the traveling polymerization front and particularly with the dependence of its constant velocity on the various involved operating conditions. 4,10,19 More recently, a mathematical model of this process has also been developed. 20 The main innovation of this model is the inclusion of the depropagation reaction, which becomes important due to the high temperature values reached in the reaction front.…”

“…The first one has a beneficial effect on the process, because too high temperatures are expected to lead to exceedingly low molecular weights of the produced polymer or to hydrogen abstraction reactions along the polymer chains leading to branched chains. Although accurate information about the structure of macromolecules produced by FP is not yet available, 10,21 this is certainly one of the open problems of these processes. On the other hand, a decrease in the front temperature is also beneficial for those systems where the adiabatic temperature is larger than the ceiling temperature.…”

Frontal atom transfer radical polymerization of tri(ethylene glycol) dimethacrylate

“…Generally speaking, the successful application of FP implies the stability of a travelling front [17,18]. At ambient pressure, stable fronts are generally descending and are found when: (i) polymers are solid at the temperature reached by the reaction wave, and/or (ii) highly viscous monomer media are polymerized.…”

“…Namely, ascending fronts are not stable due to convective motions, which cause an excessive amount of dispersed heat [17,18]. On the other hand, if in descending fronts polymers are soluble in the corresponding monomers or are molten at the temperature reached by the front, the phenomenon of 'fingering' occurs [19].…”