Impact
of initiator characteristics on the thermal stability of vinylidene chloride
copolymers |
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Authors: | B A Howell M J Johnson D E Player L J Hahnfeld S M Kling M L Mounts |
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Institution: | (1) Center for Applications in Polymer Science, Central Michigan University, Mt. Pleasant, USA, 48859-0001, MI;(2) Barrier Resins Research, Dow Chemical Company, Midland, USA, 48667, MI |
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Abstract: | Two
standard vinylidene chloride copolymers, the first containing approximately
9 mass% methyl acrylate and the second containing vinyl chloride at a nominal
15 mass% were prepared by radical suspension techniques using a series of
peroxide and azo initiators (all of approximately the same half-life temperature
for decomposition).
The nature of the initiator could impact the
stability of the resulting polymer in two ways. Instability could be introduced
either via end-group effects or by attack of residual initiator fragments
on the finished polymer during isolation and residual monomer stripping. In
this case, the relative thermal stability of the resins produced was assessed
by exposing samples to heat and shear in an air environment in a two-roll
mill (Brabender Prep-Mill). The rate and extent of degradation was most readily
apparent from color development during this treatment. The more thermally
stable polymers were produced using initiator radicals that did not attack
the polymer during isolation/stripping processes. |
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Keywords: | defect structures polymer thermal stability as a function of chain-end structure processing damage radical reactivity |
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