Attila Gungor

Adhesive and Thermo-Mechanical Behavior of Phosphorus-Containing Thermoplastic Polyimides

Abstract Thermally stable, soluble and amorphous bis(m-aminophenoxy) triphenylphosphine oxide (m-BAPPO) based polyimides were synthesized in controlled high molecular weight via solution imidization. Several dianhydrides were used to establish chemical-structure-physical property behavior. The m-BAPPO based polyimides were characterized by several techniques, including intrinsic viscosity, thermal analysis, single lap shear adhesive bond strength and thermo-mechanical behavior. The resulting phosphorus-containing polyimides were demonstrated to be thermally stable via dynamic TGA in air up to 500°C and showed 10 ∼ 20% char yield at 750°C, suggesting improved fire resistance. In addition, these polyimides showed good tensile modulus, ductile stress-strain behavior and excellent adhesion to a Ti-6A1-4V substrate, as determined by single lap shear tests. The rheological behavior was investigated by using a parallel plate type viscometer which confirmed that the materials were true thermoplastics. Tailoring t...

Soluble phosphine oxide containing aromatic polyamides

Abstract Several novel soluble phosphine oxide containing aromatic polyamides ( 3–6 ) have been synthesized by phosphorylation reactions of aromatic diacids with diamines. The presence of phosphine oxide linkages in the backbone gives these polymers superior properties, namely thermooxidative stability, high char yield and solubility in aprotic polar solvents.

Fabrication of PEEK/carbon fibre composites by aqueous suspension prepregging

Abstract Poly(ether ether ketone) (PEEK) composites were made by impregnation of continuous carbon fibres with aqueous suspensions of PEEK particles made by a novel precipitation process. These particles were suspended in aqueous solutions of ammonium salts of polyamic acids which performed two essential roles: as a polymeric dispersant and as a binder at the fibre-matrix interface. The resulting composite panels had properties that were comparable in some cases to those of commercially available PEEK composites. Fracture surface analysis from unidirectional panels suggests that the miscibility of the matrix and binder affects the failure mode at the fibre-matrix interface.

Phosphine oxide containing aromatic polyester

Abstract A phosphine oxide containing aromatic polyester has been synthesized by the direct polycondensation reaction of bis[4-( m -carboxyphenoxy)phenyl]phenylphosphine oxide (m-BCPPO) and 4,4′-isopropylidene-diphenol (bisphenol A). The presence of phosphine oxide linkages in the backbone gives this polymer superior properties: namely thermo-oxidative stability, high char yield and solubility in common organic solvents.

Water Resistance of Poly(Imide-Siloxane) Adhesives: Diffusion Coefficients by Gravimetric Sorption

Abstract Diffusion coefficients of water vapor in a polyimide homopolymer and poly(imide-siloxane) multi-block copolymers of different siloxane concentration were determined from gravimetric sorption experiments. Diffusion coefficients were of the order of magnitude of 10−8 cm2/sec. Higher levels of siloxane incorporation caused a definite increase in the diffusion coefficient, indicating a decreased resistance to water ingression. The increase in diffusion was found to be influenced by siloxane block length and was interpreted in terms of free volume and morphology. The diffusion coefficient of the 10-weight-percent PDMS copolymer, however, was found to be the same within error as that of the polyimide. This and a previous surface study suggested that an increased surface water resistance may be achieved at low siloxane concentrations without greatly increasing the bulk diffusive properties to undesirable levels.

Development of new polymeric matrices for high performance composites

Abstract High performance monomers based on the precursor trifluoroacetophenone and phenylphosphine oxide have recently been generated. The resulting monomers are important intermediates for a variety of thermally stable polymers such as polyimides and polybenzoxazoles. The pendant aryl group in both systems is nonplanar and affords polymeric systems that are amorphous as well as soluble and processable when end-capped and cyclized in solution. The aryl groups also contribute to excellent thermooxidative stability and indeed the systems are comparable to the better known ‘six F’ based systems. The phosphorus containing monomers also contribute to high glass transition temperatures, processability and flame resistance. The synthesis and characterization of processable aromatic polyimides and polybenzoxazoles will be reported. Glass transition temperatures of 420°C have been achieved with the polyimide derived from the 3F diamine and pyromellitic dianhydride. The 4-BDAF monomer has been used to obtain semicrystalline polyimides. Fully cyclode-hydrated isotropic polybenzoxazoles have also been prepared by an acid catalyzed reaction in o -dichlorobenzene at only 170°C. The resulting materials show excellent thermooxidative stability and solubility in N -methylpyrrolidinone. These materials are candidates for matrix resin and structural adhesive applications. An overview of the synthesis and characterization of these materials will be provided.