AN EXPERIMENTAL-STUDY OF PLANAR ENTRY FLOW OF RUBBER COMPOUND

An automated rheometer based on an injection molding machine is develo ped for the evaluation of entry flow problems. Several entry flow geom etries having different contraction and expansion angles and different channel lengths are tested. Two pressure transducers are flushmounted along the die length and a displacement transducer is installed to me asure the screw motion. Signals generated by the pressure transducers and displacement transducer are supplied to an A/D converter and an IB M PC/AT computer. The pressure losses for a rubber compound are measur ed between two cross-sections along the flow direction. The time evolu tion of pressure with overshoot during flow before and after the entry region is observed. At low flow rates the pressure drops of the expan sion flow are larger than those of the contraction flow. At high flow rates the pressure drops of the contraction flow become higher than th ose of the expansion flow. A ratio of the pressure drop to absolute pr essure before the entry is found to be almost independent of flow rate .