Fundamental studies on processing, characterization and properties of poly-p-phenylene terephthalamide/polyamides molecular and particulate composites

Miscibility and crystallization of poly-p-phenylene terephthalamide (PPTA) with nylon 6, nylon 66, nylon 11 and nylon 12 molecular and particulate composites have been studied. Mixtures of PPTA/nylons were prepared by coagulation in water from isotropic sulfuric solutions. The solvation of nylon 6 crystals in PPTA matrix was observed when the PPTA content exceeds 70 wt%. Cross-hydrogen bonding seems to be responsible for the virtual disappearance of nylon 6 crystals. Specific interaction between PPTA and nylon 6 macromolecules and phase separation during thermal treatment has been discussed. There is no indication of co-crystallization in the PPTA/nylons molecular composites. The PPTA/nylons systems exhibit melting point depression of nylon crystals. The Flory-Huggins interaction parameter ;The solution extrusion of PPTA with nylon 11 and nylon 12 have been studied. Mixtures of PPTA/nylon 11 and 12 were extruded through the capillary die, followed by coagulation with water. The 70/30 PPTA/nylons extrudate shows the uniaxial orientation of PPTA molecules to the machine direction. The fracture surface of the solution processed extrudates reveals the microfibrils of PPTA are uniformly dispersed. The mechanical properties of 5 wt% PPTA composition exhibit improvement in tensile modulus and tensile strength.;The PPTA/nylons molecular composites have been examined with emphasis on the rheological, mechanical and morphological characteristics. The viscosity of nylon 6 and 66 systems has increased by an order of magnitude, but decreased in the case of nylon 11 and 12 systems. PPTA/nylon 6 and 66 systems exhibit yield behavior. The extrudate swell value of 1 is measured in all composition ranges and shear rates. Low PPTA content molecular composites reveal spherical or long fibrillar morphology of PPTA phase dispersed in nylon matrices. The PPTA/nylons systems show no preferred orientation in the extrudates, but biaxial orientation in the case of compressed films. The mechanical properties of extrudates of 5 to 10 wt% PPTA compositions exhibit significant improvement in tensile modulus and tensile strength. The heat-treated extrudates show further increases in tensile modulus and tensile strength, but the elongation at break decreases.