Dynamic viscoelastic properties of polystyrene melt filled with CaCO3particles have been measured. The average size of particles is 3μm and the particle contents are 20, 40, and 60 wt%. The storage modulus G′ and loss modulus G″ increase with particle content. A second plateau appears in low frequency region for 60 wt% particle-filled polystyrene. For high-loaded samples, the relaxation spectrum H (τ) obtained from G′ curve does not coincide with that from G″ curve at long times, indicating a nonlinear behavior due to structure formation of particles. The addition of particles into polymer melt seems to depress the elasticity; the value of G′ decreases with increasing particle content if comparison is made at the same value of G″. The φ dependence of relative modulus G′(φ)/G′(0) becomes strong with decreasing ω. The relative modulus in rubbery plateau, G′(φ)/G′(0) at high ω (≥100 s-1), is expressed by exp (2.78 φ).
A capillary rheometer to achieve an extremely high shear rate was developed and applied to some single polymer systems and blends of immiscible polymers. Flow curves of polycarbonate (PC), styrene-acrylonitrile copolymer (SAN) and their blends were obtained up to the shear rate of 107 s-1. Only a first non-Newtonian region was observed for PC in the region. A second Newtonian region was observed for SAN in a high shear rate region (>2.7×106 s-1); an increase in the viscosity was found at a shear rate of about 4 × 106 s-1, above which the second non-Newtonian region appeared. Flow curves for immiscible polymer blends of SAN and PC were similar to that of the SAN with the three characteristic regions. The second Newtonian behavior began at a lower shear rate for blends than that for the SAN. For the calculation of the viscosity-shear rate curves of blends, a concentric multi-layer model was proposed. It gave good agreement between the calculated and the measured values. It was generally confirmed by this model that viscosity of immiscible polymer blend is much affected by the component of lower viscosity (SAN in this case) because the shear rate of the layer of lower viscosity component is higher than that of the higher viscosity component in any flowing immiscible binary system.
Dynamic viscoelastic responses were explored on isotactic polypropylene (i-PP) melt (Mv=1.61×105, Mw/Mn=4.4) and 1% 1, 3; 2, 4-p, p′-ditoluyliden sorbitol (PDTS)/i-PP system in order to investigate sol-gel transition of PDTS in polymeric media. The storage modulus G′ and the dynamic viscosity η′ were obtained as a function of temperature in the cooling process from 250 to 130°C for i-PP and from 250 to 150°C for PDTS/ i-PP system at angular frequencies of 10-4, 1, 10, 102rad/s. The results indicated that 1% PDTS/i-PP system has a sol-gel transition temperature Tfg=201°C, which is identified as the critical temperature for formation of the PDTS percolation network. The master curves of G′ and η′ are obtained for the sol and gel regions of 1% PDTS/ i-PP system assuming the thermorheological simplicity in each region. The master curves for the sol region of 1% PDTS/i-PP system are found to be nearly identical with those of the bulk i-PP melt. However, they were found to be quite different from those for the gel region, especially at low frequencies (corresponding to the terminal flow region of the sol); the gel exhibited a significant increase of η′ and a plateau in G′ curve, as well. The loss tangent, tanδ, for the gel was around 1 in the whole frequency range measured. These results for the gel imply that (i) the PDTS aggregates into a percolation network of a large spatial scale, and that (ii) the association of the dissolved PDTS in the matrix into the networks and the dissociation of the PDTS molecules in the networks into the matrix are in dynamical equilibrium, giving rise to the large tanδ. A model of the sol-gel transition was presented.
Characteristics of flow curves for the blends of immiscible polymers, whose flow curves intersect each other, were investigated by computer simulation based on the concentric multi-layer model proposed previously. Flow curves of component polymers were approximated by the power-law. Calculations were performed for a few combinations of power-law indexes and for various blending ratios. Following results were obtained. (1) Flow curves for the blends with various ratios intersect at the same point as those of parent polymers do. (2) Flow curves lie in the order of blending ratio. (3) Flow curves are similar to that of a lower viscosity component at either side of the cross point on flow curves of parent polymers. (4) The region on flow curves, where the conventional blending rules on viscosity are applicable, depends on the ratio of power-law indexes of parent polymers and the value of shear rate and viscosity at the cross point. A good agreement between predicted and experimental results were attained for the blends of polystyrene and high density polyethylene.
Unsteady rheological properties of liquefied soil in the Chiba-ken Toho-oki (East-off Chiba pref.) Earthquake were measured by means of parellel-plate rheometers. The size (the longest diameter) of the soil particle was distributed from 30 to 300 μm and the average was about 95 μm. The soil shows a typical flow curve of a heterogeneous system having a yield stress. The yield stress of the soil suspension is proportional to c7.7in the concentrations below 71 wt% and to c67at the higher concentrations where the soil liquefies during the course of cyclic strain applications. The dynamic rigidity decreases to about 1/10 to 1/40 of the initial value by the cyclic strain.