ABSTRACT
Epoxy (EP) was copolymerized with polyamic acid (PAA, precursor of polyimide (PI)) with termanil monomers of (1) 4,4'-Oxydianiline (ODA) and (2) pyromellitic dianhydride (PMDA) individually to form (PI-O-EP) and (PI-P-EP) copolymers. The FTIR spectrum of PI-O-EP copolymerization intermediates shows that some amide-EP linkages were formed at low temperature and were broken at higher temperature; in additoin, the released amide was available for subsequent imidization to form PI. The curing and imidization of the amide groups on PAA were determined by reaction temperature (kinetic vs. thermodynamic control). In PI-P-EP, the released amide group was very short-lived (fast imidization) and was not observed on FTIR spectra. Formation and breakage of the amide-EP linkages is the key step for EP homopolymerization and formation of the interpenetration network. PI contributed in improving thermal durability and mechanical strength without compromising EP's adhesion strength. Microphase separations were minimal at PI content less than 10 wt%. The copolymerization reaction in this study followed the "kinetic vs. thermodynamic control" principle. The copolymer has high potential for application in the field of higher-temperature anticorrosion.
ABSTRACT
The polyimide/multi-walled carbon nanotubes (PI/MWNTs) nanocomposite film has been successfully synthesized in this study. The source of MWNTs is prepared by chemical vapor deposition (CVD) method. Then the MWNTs are washed with acid for purification before being added into the polymer matrix. The acid-modified procedure aids in dispersing MWNTs in N,N-dimethylacetamide (DMAc) solvent. Based on the results of field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM), the MWNTs are embedded in PI and well-dispersed within the PI matrix. The dynamic mechanical analysis (DMA) shows that the storage modulus of nanocomposite film is increased by 68% with the addition of 1 wt% MWNTs into PI. The nanocomposite films start to decompose at or above 400 degrees C and lose 5% of its weight at 545 degrees C according to thermogravimetric analysis (TGA). Meanwhile, the electrical conductivity of the nanocomposite film with 3 wt% MWNTs, is raised more than 10 orders of magnitude from 10(-15) to 10(-5) S/cm.
