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

• Published in: Journal of polymer science. Part A, Polymer chemistry Polymer chemistry, 1995-03, Vol.33 (4), p.643-652
• Main Authors: Pojman, John A., Willis, Jason, Fortenberry, Dionne, Ilyashenko, Victor, Khan, Akhtar M.
• Format: Article
• Language: English
• Subjects: adiabatic polymerization; ceiling temperature; conversion; frontal polymerization; molecular weight distribution; propagating polymerization fronts; temperature profiles; traveling waves
• ISSN: 0887-624X; 1099-0518
• DOI: 10.1002/pola.1995.080330406

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.