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Disclosed is a method to tailor the properties of polyimides made from mixtures of polyamic acids.
English (United States)
This text was extracted from a PDF file.
This is the abbreviated version, containing approximately
77% of the total text.
Page 1 of 1
Method for Tailoring Polyimide Blend Properties
Disclosed is a method to tailor the properties of polyimides made from
mixtures of polyamic acids.
Mixing of two or more different homo-polymers leads to new materials which
can exhibit the preferable properties of both homo-polymers. Property variations
are realized by varying the ratio of the starting materials.
Mixtures of polyamic acids are also expected to give new materials which,
after curing, should result in polyimide mixtures. Contrary to most other polymers,
solutions of polyamic acids are reactive. In the presence of two or more differing
polyamic acids exchange reactions occur. These reactions involve chain
cleavage, forming reactive end groups. The latter react with suitable partners,
forming again polyamic acid. If more than one type of polyamic acid is present,
cross-reactions (exchange reactions) will occur. The resulting materials are no
longer homo-polymer mixtures but mixtures of homo-polymers and co-polymers.
The composition of the co-polymers depends on the extent of the exchange
The extent of exchange reactions can be influenced in two different ways:
through the mixing time at relatively low temperatures, and through the curing
Formation of reactive groups through chain cleavage occurs not only in
solution but also during the solid-state cycloimidization of polyamic acids.
Therefore, exchange reactions are possible also during the cure of polyamic acid
mixtures. At the el...