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Crosslinking characterization of a polyimide: AFR700B
Author(s) -
Russell John D.,
Kardos John L.
Publication year - 1997
Publication title -
polymer composites
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.577
H-Index - 82
eISSN - 1548-0569
pISSN - 0272-8397
DOI - 10.1002/pc.10311
Subject(s) - differential scanning calorimetry , glass transition , materials science , dynamic mechanical analysis , kinetics , fourier transform infrared spectroscopy , arrhenius plot , polyimide , swelling , reaction rate constant , polymer chemistry , arrhenius equation , composite material , activation energy , polymer , chemistry , chemical engineering , thermodynamics , physics , layer (electronics) , quantum mechanics , engineering
Crosslinking in AFR700B polyimide was studied using several techniques. Crosslinking could not be detected using Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). Swelling in n‐methyl pyrrolidone (NMP) showed network formation occurs at cure temperatures ≥325°C (617°F), but the reaction kinetics could not be determined from the data. Dynamic mechanical analysis (DMA) studies have shown that the storage modulus ( G ′) increased with increasing cure temperature up to 350°C (662°F), and was constant above 350°C (662°F), indicating that crosslinking via the reverse Diels‐Alder reaction was occurring. A broad secondary transition was seen in the loss modulus ( G ″) curves, centered between 150 and 180°C (302 and 356°F). This secondary transition appeared at a cure temperature of 300°C (572°F) and became more dominant with increasing temperature and time. This secondary transition was not seen for cures <300°C (572°F) when the chains have not crosslinked. Therefore, this is likely due to a crosslink bond rather than one in the backbone. At 1 atm, crosslinking followed second‐order kinetics based on the increase in glass transition temperature ( T g ). The Arrhenius plot of the rate constant showed a break in the slope, possibly indicating a change in reaction mechanism. At 1.38 MPa (200 psi), the T g data was too scattered to determine the kinetics.