THE HORIZONTAL STRETCHING OF TEST LIQUID M1

Tests are described in which a polybutene/kerosene-based liquid (supplied by Dr. T. Sridhar) is stretched horizontally in a simple new apparatus. Liquid issuing from a nozzle is pulled horizontally onto the surface of a cylinder rotating about a vertical axis. Tests are of two types. In the first type, photographs of stretching jets are taken and the stress, strain and strain rate found at equal intervals along the jet. In the second type, with shorter filaments, the speed of rotation of the cylinder is raised progressively and the same quantities are determined over the full length of the jet. The extensional viscosity rises with distance along the jet and, for the two longer jets, reaches a steady level of the order 104 Pa s towards the high-speed end of the jet. This corresponds to a Trouton ratio of 3000; values of up to 6000 are obtained during experiments of the second type. A plot of extensional stress against extensional strain rate shows marked scatter of the experimental points, whilst a plot of extensional stress against total strain gives lower gradients for experiments of the first type than for those of the second type. It is clear from this plot that decreased time of stretching produces increased stress and it is shown that total strain divided by total stretching time controls the extensional stress, under the conditions used. Using this as a measure of extensional strain rate, the extensional viscosity for all tests becomes 110 Pa s, giving a Trouton ratio of 35. The test fluid is stated to combine the properties of a liquid with those of a weak rubberlike solid. The results are discussed and it is suggested that interested workers should contact the author in order to obtain copies of the raw data. Extensional strain rates vary from 2 to 17 s-1 and stretching times from 80 to 700 ms. © 1990.