FLOW BIREFRINGENCE MEASUREMENTS IN A CALE NDER GAP

Velocity profiles and the various components of the stress tensor with in the flow field of viscoelastic liquids in the gap between two rotat ing rolls of a calender are very complex despite the simple geometry o f the apparatus. For the measurement of the stressfield in the gap bet ween the two rolls, the optical birefringence method was used in fluid s with viscoelastic rheological behaviour. The local principal stresse s are calculated from the stress optical law using measurements of the anisotropy of the sheared fluid for the penetrating monochromatic bea ms of laser light by means of the stress optical law. A polyisobutene melt of low molecular weight is used as the liquid.