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Physicochemical characterization of alloy of polyimide with varying degree of crosslinking through diisocyanates
Author(s) -
Rajani S.,
Jain S.,
Verma M. M.,
Dubey M.,
Nema S. K.
Publication year - 1999
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.11550
Subject(s) - polyimide , materials science , isocyanate , solvent , curing (chemistry) , polymer chemistry , chemical engineering , alloy , composite material , organic chemistry , polyurethane , chemistry , layer (electronics) , engineering
Abstract Polyimide alloys are prepared by blending the crosslinked and uncrosslinked polyamic acid components and followed by thermal imidization. The blend components can be synthesized by the reaction of polyamic acid with the varying concentration of crosslinker [here methylene bis (4‐phenyl isocyanate or MDI)] from 1.54 × 10 −2 mol/L (i.e. hypothetically calculated critical crosslinker concentration or CCC) to 1.54 × 10 −6 mol/L. This communication discusses the synthesis and characterization of polyimide (PI) blends and alloys prepared by varying degrees of crosslinking introduced via isocyanate‐amic acid reaction. The polyimides were prepared by thermally imidizing the polyamic acid blends at different curing temperatures from 50°C to 350°C. The degree of imidization and residual solvent content for blends having varying mole fractions of crosslinked (or branched) and uncrosslinked components and two extreme conditions and at specified temperature‐time profiles have been studied. The resultant PI‐MDI blends have exhibited synergism on mechanical properties. The improvement in mechanical properties, however, was significantly higher at the lower imidization temperature (i.e. 50°C to 150°C). The feasibility of preparing polyimide alloys with synergistic combinations of crosslinked and uncrosslinked polyimide components was inferred.