autoacceleration


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autoacceleration

[¦ȯd·ō·ik‚sel·ə′rā·shən]
(organic chemistry)
The increase in polymerization rate and molecular weight of certain vinyl monomers during bulk polymerization.
References in periodicals archive ?
However, during propagation, the reaction kinetics are affected by autoacceleration, which is a consequence of altered diffusion.
This effect, causing autoacceleration of the polymerization reactions, was first reported by Norrish and Brookman [32] on poly-methyl methacrylate (PMMA) polymerizations.
However, the various phenomena of autoacceleration, unequal reactivity of different functional groups, multiple termination processes, volume shrinkage, and the heterogeneities of the networks formed make the understanding of the mechanisms difficult.
ABSENCE OF AUTOACCELERATION IN AROMATIC SULFONYL AZIDES AS FREE-
The main motivation to search for other models for the simulation of the photopolymerization process was to see the effects of autoacceleration, autodeceleration, volume shrinkage, and reaction diffusion terms on the system besides the basic photopolymerization reaction mechanisms of initiation, propagation, and termination.
6 and 7, some typical features of the curing process are represented, such as autoacceleration and autodeceleration, which are in agreement with theoretical predictions.(14), (19) The photopolymerization rate strongly depends on the mobility of the reactive chain ends, whereas the termination reaction is affected by the reduced mobility of the radical sites bound to the developing network.
ABSENCE OF AUTOACCELERATION IN AROMATIC SULFONYL AZIDES AS FREE-RADICAL INITIATORS FOR PHOTOPOLYMERIZATION
Unlike as reported in this paper for nylon fibers, the property gradients in polypropylene fibers were attributed to autoacceleration by surface oxidation during processing or screening by UV absorbing additives.
The data illustrates autoacceleration immediately after irradiation commences so that the reaction rate reaches a maximum value at a double bond conversion of about 10%.
As the conversion increases, the mobility of polymer radicals decreases due to the increased viscosity and entanglements, which causes a slower rate of termination and higher rate of polymerization (autoacceleration).
With the process of reaction, three-dimensional gel structure is formed, which restricts the diffusion and mobility of macroradicals and pendant double bonds, slowing down the radical termination rate, which leads to autoacceleration. With the reaction going on, the increasing cross-linking will limit the radicals and monomer's mobility and result in the end of reaction eventually.