In our previous work, the miscibility and rheology behaviors of poly(3-hydroxybutyrate)/poly(p-vinylphenol) (PHB/PVPh) blends with homogeneous amorphous compositions had been studied. In this work, the rheological characteristics and physical gelation point have been investigated for the miscible PHB/PVPh blends with crystalline/amorphous compositions. The time sweep and frequency sweep of dynamic oscillatory experiment are discussed in details. The storage modulus G' and loss modulus G'' grow gradually along with the isothermal crystallization time, but the storage modulus G' exceeds the loss modulus G'' in the end. The physical gelation phenomena can be observed according to the power law method. In the flat region of loss tangent vs. angular frequency curves, the physical gelation point (tg) of the PHB/PVPh 90/10 comes forth prior to the PHB/PVPh 80/20 during the liquid-solid transition process, which results mainly from the various isothermal crystallization rate of PHB component within PHB/PVPh blends.

Keywords: crystallization; dynamic rheology; poly(3-hydroxybutyrate); physical gelation point (tg)