Effects of dianhydrides on the thermal behavior of linear and crosslinked polyimides

Abstract

To determine the thermal characteristics of linear and crosslinked polyimides (PIs), BTDA, ODPA, and 6FDA were used to synthesize polyimides. Thermal degradation temperature and glass transition temperature of the resulting PIs were measured using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). To measure the change in modulus and coefficient of thermal expansion (CTE) depending on dianhydride structure, a dynamic mechanical analyzer (DMA) and thermo-mechanical analyzer (TMA) were used. The thermal degradation and glass transition temperature properties of linear PIs varied according to whether the linear chain adopted a bulky or flexible structure. Dynamic modulus and thermal expansion values of linear polyimides also showed good agreement with the TGA and DSC results. As we expected, linear polyimide with bulky 6FDA groups showed better thermal behavior than the flexible polyimides. Crosslinked polyimide nadic end-capped (norbornene) with a bulky dianhydride group had a lower thermal degradation temperature and higher CTE than flexible BTDA and ODPA polyimides. Our results indicate that the mobility of the dianhydride group affects the thermal behaviors of linear and crosslinked polyimides in different ways.

The effect of the ring opening polymerization and chain spacing on the coefficient of thermal expansion and modulus of polyimide

“…In our previous study, we have confirmed the behavior on change of dianhydrides with the property of the NE crosslinked PI . However, the mechanism of norbornene crosslinking has not been elucidated precisely.…”

Molecular weight controlled poly(amic acid) resins end‐capped with phenylethynyl groups for manufacturing advanced polyimide films

“…It is noteworthy that the aggregation structure of PI film is intensely affected by the variables that control the thermal‐curing process, e.g. temperature and time, which in turn would directly play a critical role in dictating mechanical and thermal properties . It was expected that thermal transitions and concomitant morphology changes caused by the thermal‐activated, free‐radical‐predominant curing of phenylethynyl functional group under various processing conditions should be indicative of the curing behavior and mechanical response of PI films.…”

Electrospinning of in situ and ex situ synthesized polyimide composites reinforced by titanate nanotubes

“…The mechanism involved in the change of glass transition is probably related to the strong interaction between nanostructured titanates and polyimide resulting in more restriction in polymer chains mobility via steric hindrance. Also, strong covalent bond may occur between hydroxyl group on the surface of titanate nanotube and amino group of polyamic acid during imidization resulting in branching the polymer chain and leading to crosslinking, which usually increases the glass transition temperature in polyimide …”