Design of polymer blend rheology: 4. Effect of polymethacrylic ionomers on the melt viscosity of polyamide m x D,6

Rheological properties of blends of polyamide m x D,6 (PA) with random copolymers of methyl methacrylate and methacrylic acid (P(MMA-co-MAA)) and the related ionomers (P(MMA-co-metal MA)), respectively, have been investigated at 260°C. Addition of small amounts of suitable ionomers (up to 5 wt%) remarkably increases the melt viscosity of PA. At low shear rates and depending on the metal cation of the ionomer, the rheofluidity of PA is reduced by at least two orders of magnitude. The PA melt viscosity increases with the cation as follows: Ni2+ < Ba2+ < Mg2+ < Li+ < Na+ < K+ < Cs+. The major effect is believed to occur when the polymer compatibility is improved to the point where a finely dispersed two-phase system with a low interfacial tension is reached, as a result of strong ion-dipole interactions. Polyblends show a rheothinning behaviour which agrees with the reversibility of H-bonding and dipolar interactions.