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The effect of composition drift and copolymer microstructure on mechanical bulk properties of styrene‐methyl acrylate emulsion copolymers
Author(s) -
Schoonbrood Harold A. S.,
Brouns Harry M. G.,
Thijssen Henk A.,
van Herk Alex M.,
German Anton L.
Publication year - 1995
Publication title -
macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 1022-1360
DOI - 10.1002/masy.19950920113
Subject(s) - copolymer , styrene , emulsion , materials science , microstructure , acrylate , polymer chemistry , chemical engineering , composition (language) , composite material , polymer , engineering , linguistics , philosophy
In order to determine the influence of composition drift and copolymer microstructure on the mechanical bulk properties of styrene ‐methyl acrylate copolymers, several copolymers were produced by emulsion copolymerization. Three different average compositions were used. By performing the copolymerizations under batch and semicontinuous conditions with two different monomer addition strategies (starved conditions and optimal addition) it was possible to control composition drift and to produce copolymers with different microstructures (chemical composition distributions). All these copolymers were processed in a way that ensured that the original particle structure was lost before the polymers were tested. It was found that composition drift had an influence on the mechanical properties (Young's modulus, maximum stress, elongation at break). This influence could be understood very well on the basis of present knowledge about structure‐mechanical properties relationships. In the case of homogeneous copolymers maximum stress and elongation at break are dependent on the molecular weight, and only weakly dependent on the chemical composition, and Young's modulus is independent of chemical composition and molecular weight in the range of compositions investigated, as expected. In the case of heterogeneous copolymers, the influence of copolymer microstructure on Young's modulus, maximum stress and elongation at break is very large. Depending on the extent of control of composition drift during the polymerizations, phase separation was observed in the processed polymers, and the presence of a rubber phase affected the properties profoundly.