SynopsisCommercial guargum is known to be a shear stable drag reducing agent. However, the aqueous solutions of guargum start degrading within 8 hrs. of their preparation and after 65 hrs., they degrade completely. In the present investigation, the graft copolymers of guargum and polyacrylamide have been prepared. It has been shown that the purification and grafting enhance the drag reduction effectiveness and biodegradation resistance considerably in guargum.

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SynopsisAn extensive study on the turbulent drag reduction caused by the various mixtures of polyacrylamide, purified guargum, xanthangum, and their graft copolymers has been conducted at low concentrations and Re = 14,000 using a turbulent flow rheometer. It has been found in most of the cases that the drag reduction caused by mixtures shows a positive deviation from the linearly additive straight line. This effect is more prominent when the drag reduction caused by both the constituents differ appreciably. In most of the cases, the drag reduction caused by the mixtures is higher than the DR caused by either of the constituent polymers; however, the drag reduction caused by the mixture is less than the sum of the drag reduction caused by both the constituents at their respective concentration in the mixture. I t has also been noticed that there is no evidence of synergism in these mixtures at low concentrations.

Abstract:The shear stability of drag reducing polymer-polymer and polymer-fibre mixtures has been studied at a Reynolds number of 14,000 using a turbulent flow rheometer. The ratio of the drag reduction at a particular pass number to the initial drag reduction has been determined for the mixtures at various pass numbers and compositions in order to determine the effect of composition on the shear stability of the mixtures.It has been found in both cases that when there is a drastic difference in the shear stabilities of the constituents of the mixtures, the incorporation of a small amount of the less shear stable drag reducing agent reduces the shear stability drastically. On the other hand, when the shear stability of the constituents are of the same order, there is only a proportional change in the shear stability of the mixtures on addition of one component to the other. A correlation between the decay coefficient of the mixture (RM), the decay coefficients of the constituents (R 1 and R2) and the weight fractions of the mixture components (W 1 and W2) is suggested. An efficacious method for preparing asbestos fibre stock suspensions is also described.