Jan M. Stouffer

Copolymer modification of nylon-6,6 with 2-methylpentamethylenediamine

Polyamides were prepared in which part or all of the hexamethylenediamine (HMD) in nylon-6,6 was replaced by its isomer, 2-methylpentamethylenediamine (MPMD). The intermediate compositions are considered random copolymers between the two homopolymers (66 and MPMD-6). The crystalline properties of these polymers were studied by differential scanning calorimetry, X-ray diffraction and optical microscopy. It was concluded that the two kinds of units, 66 and MPMD-6, do not co-crystallize. In copolymers containing large fractions of HMD, the MPMD units are excluded from the crystals. With appropriate thermal treatment, MPMD-6 can crystallize with two different unit cells and a variety of spherulitic morphologies. The two crystal forms can be distinguished by their crystallization, melting and optical properties. The crystallization kinetics of the copolymers are slower than those of the homopolymers, which is associated with the slower rate of nucleation formation rather than the transport ability. This is consistent with the dielectric results, which showed that the glass transition temperatures of the different copolymers are similar. It was found that MPMD-6 can be quenched into an amorphous state. The properties of the amorphous portions were further investigated through dielectric relaxations. Although, the incorporation of MPMD tends to shift the dielectric gamma relaxation towards higher temperatures, the total effects of variations on chemical structure were much smaller than those which pertain to the crystalline phase.