Thermal
degradation of vinylidene chloride/4-vinylpyridine copolymers |
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Authors: | B A Howell P B Smith |
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Institution: | (1) Center for Applications in Polymer Science, Central Michigan University, Mt. Pleasant, USA, 48859-0001, MI |
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Abstract: | Vinylidene chloride polymers are prominent in the
barrier plastics packaging industry. They display good barrier to the transport
of oxygen (to prevent spoilage of food items) and flavor and aroma constituents
(to prevent 'scalping' on the supermarket shelf). However, these
polymers undergo thermal dehydrochlorination during processing. This can lead
to a variety of problems including the evolution of hydrogen chloride which
must be scavenged to prevent its interaction with the metallic walls of process
equipment. Such interaction leads to the formation of metal halides which
act as Lewis acids to facilitate the degradation. A potentially effective
means to capture hydrogen chloride generated might be to incorporate into
the polymer a mild organic base. Accordingly, copolymers of vinylidene chloride
and 4-vinylpyridine have been prepared and subjected to thermal aging. Results
suggest that the pyridine moiety is sufficiently basic to actively promote
dehydrochlorination in the vinylidene chloride segments of the polymer. |
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Keywords: | barrier polymers NMR spectroscopy stabilization vinylidene chloride copolymers |
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