Styrene self polymerization kinetics 3

[jeanot]

I am looking for the rate of (self) polymerization of styrene as a function of time and temperature. The intention is to estimate the content of polymer (polystyrene)that can be formed in a liquid styrene monomer pipe.
Thanks.

 

[moltenmetal]

Is the styrene inhibited, or uninhibited? The inhibitor is of course there to reduce the likelihood of unwanted polymerization. The inhibitors are free radical scavengers, and dramatically limit the rate of autopolymerization. How you would estimate the autopolymerization rate in the presence of inhibitors is unknown to me.

Uninhibited styrene can very rapidly result in autothermal (runaway) polymerization if it gets started. Plugging the line or increased viscosity from the presence of polymer will be the least of your worries. Relief design will require great care. I've seen a 24" diameter uninhibited styrene tank with a 4x10" relief valve on it for that reason...Check the guidelines for safe storage and handling of styrene published by various styrene suppliers.

 

[jmw]

I wonder hw closely this behaviour is similar to that of methyl methacrylate polymerisation? There is a good article somewhere on the SOlartron Mobrey site (

http://www.solartronmobrey.com)

under articles i think, where the batch polymerisation of methylmethacrylate was initially control at Atohass (holland?) by taking samples at intervals during the reaction and measuring the viscosity quite crudely with a cup viscometer. By plotting this againmst time they are able to estimate the end point as the time at which they must quench the reaction. The batch run is usually of around 2 hrs with a very tight end point window which occurs during an exothermic phase of the reaction. They later introduced a digital viscometer (Solartron) which actually measured the viscosity continuously. This enabled them to detect, rather than predict, the end point and they eliminated a 10% missed end point rate.
I refer to this because it is documented. However, i know a similar excercise was successful in pipeline continuous polymerisation process but have no details. Viscosity is a good indicator of molecular weight (ASTM D 2512? or something like that).

JMW

http://www.viscoanalyser.com

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[bchoate]

bchoate[/b]
Styrene condenses with itself in a Diels-Alder reaction to form a dimer (Diels-Alder adduct)which acts as a free radical initiator. Polymerization proceeds by free radical initiation. The of formation of the diels-alder adduct and of polymer is temperature dependent.

The definitive work on styrene thermal polymerization can be found in an article by Albert Hui and Archie Himielec.
J. Applied Polymer Science, Vol. 16, 749-769, 1972. At 140 C styrene conversion is about 20% after 1 hour.

Inhibitors act to minimize polymerization under normal storage condition. As temperature increases free radical production increases and the inhibitor is overwhelmed.
Bill C

 

[25362]

Left alone even at room temperature, styrene will eventually polymerize with itself to a clear glassy solid.
A known polymerization inhibitor for styrene and butadiene is para-tert-butyl-cathechol usually called by its acronym PTBC. Dosages are around 10 ppm.