1. n. [Drilling Fluids]
Hydroxypropyl starch is a derivative of natural starch, used primarily for fluid-loss control in drilling muds, drill-in, completion and workover fluids. Being nonionic, it is only slightly affected by salinity and hardness in fluids. Linear and branched carbohydrate polymers in natural starch have three reactive OH groups on each glucose unit. During manufacture, these polymers are reacted with propylene oxide, adding hydroxypropyl (CH(OH)CH2CH3) groups at the OH positions by an ether linkage. By adding the hydroxypropyl groups, the HP starch becomes more resistant to thermal degradation and bacterial attack.
Alternate Form: HP starch