y polyoxypropylene is between approximately 5000 and 7000 daltons;a is a number such that the portion represented by polyoxyethylene constitutes between approximately 10% to 40% of the compound by weight, and; b is a number such that the polyoxypropylene portion of the total molecular weight of the octablock copolymer constitutes between approximately 60% and 90% of the compound by weight. 2.