毛细管流变仪RG25

In this work the unsteady-state contact angle at the interface between polymer melt and carbon black (CB) was measured. The transition of contact angle from an unsteady to a steady state can be divided into three stages, the unsteady thermo-stage, the wetting stage, and the reach of equilibrium contact angle. Subsequently, three critical indices, the unsteady heat-transfer period t0, the retardation time τ, and the contact angle at equilibrium state A∞ are defined herein. The decrease in contact angle against time can be simulated by an exponential decay that involves these three critical indices. Molten polypropylene (PP) and polystyrene (PS) have the smallest equilibrium angle A∞, followed by polybutylene terephthalate (PBT), and polymethyl methacrylate (PMMA) has the greatest angle. Interestingly, this order is strongly related to the solubility parameter of each polymer. The CB coated with sulfonated polyester slightly changes the equilibrium angle A∞, but drastically reduces the retardation time τ for PP and PBT. This finding indicates that the CB, whose surface is modified by sulfonated polyester, can effectively reduce the compounding time of PP and polyester. Experimental results also reveal that reduce compact density slightly increases A∞ but barely affects τ. Furthermore, modifying PS with polybutadiene particles yields a high contact angle A∞ and a low τ value.