Synthesis, Development and Characterization of Some Advance Matrix Materials

Abstract

Phthalonitrile resins are high temperature thermosetting polymers, which are considered ideals materials for marine, aerospace, and electronic applications. The synthesis of phthalonitrile monomers with self-catalyzing nature and with large processing window – defined as the temperature between the melting temperature of the monomer and the gelation temperature of the polymer network–, are gaining much more importance because of ease in processability and high thermal stability. In the present study, some novel phthalonitrile resins were synthesized using ortho- linked phthalonitrile monomers and self-catalyzing phthalonitrile monomers with different linkages such as: ether, imide-ether, and amide-ether between the reactive ends. All the synthesized monomers were characterized by spectroscopic techniques such as FT-IR, 1 H-NMR and 13 C-NMR. FT-IR indicated absorption peaks around 1522 and 1355 cm -1 and around 1010 cm -1 indicated the formation of triazine and phthalocynine rings (heterocyclic rings formed as a result polymerization) respectively after post curing. The thermal analyses were carried using DSC, TGA, DMA, and Rheometery. DSC and rheometric studies showed that the monomers with ortho linkages have low melting point and high crosslinking temperature. In self-catalyzed monomers, the monomers having amino group at ortho position or 1,2-linked (ortho) monomers have broad processing window. The complex viscosity (η*) was very low (<1 Pa.s) in between melting and the crosslinking temperature, which is highly suitable for resin transfer molding, resin infusion molding, and filament winding. TGA studies revealed that the resin synthesized from the monomer with heterocyclic ring shows high thermal stability and residual mass (char yield). The thermal stability of the polymer having ether or imide-ether linkages are nearly the same but more than the polymer having amide-ether linkage, indicating the effect of crosslinking density and structural changes. DMA measurements showed that storage muduli (E') and glass transition temperature (Tg) enhance with the increase of curing temperature. These meaurements also indicated that the polymers having imide-ether and amide-ether linkages have higher storage moduli than the polymers have only ether linkages.