Rheology and processing of talc filled thermoplastics.

摘要

We describe a study of the rheology and processing of talc filled thermoplastics. Processing operations such as annular die extrusion, blow molding, compression molding, and thermoforming are carried out to investigate the influence of talc particles on polymer processing.; Talc particle orientation in various simple viscometric flows is characterized using wide angle x-ray diffraction. The talc particles being disc-like in shape orient with the disc normals perpendicular to the flow direction. The discs orient with their surface parallel to the plate surface of the sandwich, cone-plate, and parallel plate rheometer. The surface of discs orients along the flow direction to the capillary and elongational rheometer.; A broad range of experimental measurements of the shear, elongational, and oscillatory flow behavior on thermoplastic melts with high loadings of talc particles is presented. The viscosity increases with increasing particle loading and with decreasing particle size. The talc filled thermoplastic melts with smaller particles at higher loadings exhibit yield values i.e. stresses below which there is no flow.; The implication of yield values in anisotropic compounds is considered. A 3-dimensional rheological model has been developed to interpret the anisotropic and plastic characteristics of talc-thermoplastic compounds. The anisotropic plastic visocoelastic fluid model is specialized to transversely isotropic form to represent the behavior of suspensions of oriented disc particles.; The influence of talc particles on the crystallization behavior of talc filled thermoplastics is determined using differential scanning calorimetry. The rate of crystallization increases with increasing particle loading and with decreasing particle size.; The annular extrudate swell and sag behavior of neat and talc filled high density polyethylene are investigated under isothermal conditions using a flow visualization technique. The annular extrudate diameter and thickness swell decreases with increasing particle loading and with decreasing particle size. The annular extrudate sag decreases with increasing particle loading and with decreasing particle size.; The particle and polymer chain orientation in blow molding, compression molding, and thermoforming is investigated using a wide angle x-ray diffraction pole figure technique. The results are represented in terms of orientation factors.