ISSN:
0025-116X
Schlagwort(e):
Chemistry
;
Polymer and Materials Science
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
,
Physik
Notizen:
While in solution or bulk radical polymerization, only one azeotropic copolymerization can be observed at the best- if reactivity ratios are both 〉 or 〈 1, on the contrary in emulsion batch copolymerization, many more such azeotropic copolymers can be synthesized. Monomer partitioning between droplet, water and particle phases is at the origin of this behaviour of a particular interest, hence water solubility of the monomers plays a determining role. Experimental works confirm the theoretical predictions derived from an approach, based on partition coefficient and thermodynamics, which allows to compute the optimum monomer/water ratio to be used, in order to get, in a batch process, a copolymer of constant composition up to high conversion. The optimum depends upon reactivity ratios, monomer water solubility, monomer feed composition. Examples are given for acrylonitrile/methyl acrylate copolymerizations. It appears that it is not any more Lecessary that they are both greater or lower than unity; for instance, batch emulsion copolymerizations of acrylonitrile/butyl acrylate (rAN = 0.89; rBuA = 1.2) result in homogeneous copolymers at the optimum monomer/water ratio, in the whole range of monomer feed. The approach can also be applied to semi-continuous process to select the best experimental conditions to “tailor” the copolymer.
Zusätzliches Material:
9 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/macp.1985.020101985114
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