The application of blending law on linear viscoelastic properties of linear-star and star-star polymer blends

A quadratic binary blending law of the terminal relaxation spectra is used to predict the viscoelastic properties of star-star and linear-star polymer blends. The results are compared with the experimental data reported by St ruglinski et al. Star polymers with long arms are assumed to dominate the r elaxation behavior of the star-star polymer blends. In the linear-star poly mer blends, star polymers are assumed to dominate the relaxation behavior. The 'iso-relaxation time' approach is proposed to represent the linear chai n by an equivalent star chain for the linear-star polymer blends. The predi cted viscoelastic properties agrees with the experimental observation Very well. Also, the well known relation, (J(e)(o))(b) proportional to 1/v(2) (v (2) is the volume fraction of long-arm star chains), can be deduced from th e binary blending law for the concentrated long-arm star chains entangled w ith much shorter chains. Furthermore, it also predicts that it would system atically depart from the relation. (J(e)(o)) proportional to 1/v(2), when t he molecular weight of shorter chain becomes closer to the molecular weight of long-arm chain. In the limit, M-1/M-2 = 1, the relation is switched to (J(e)(o))(b) proportional to v(2). (C) 1999 Elsevier Science Ltd. All right s reserved.