10 u03bcm 60 u03bcm with a density of 0 4 g cm various thermoplastic materials were co extruded with glass microspheres using a 33 mm co rotating twin screw extruder sterling extruder corporation plainfield n j with a length to diameter ratio of 24 1 multiple feed ports fitted with an underwater pelletizer gala industries eagle rock va two volumetric feeders accurate dry materials feeder whitewater wis were used to feed additives into the extruder with a screw speed of 250 rpm resulting in a die output rate of 5 7 pounds hr u02dc 2 6 kg hr the material was fed in a polymer glass microspheres weight ratio of 12 7 7 3 the compounding temperature range from hopper to die is cited in table 1 below pelletized material is dried at room temperature for several days before packaging for examples 6 10 composite microspheres 1 0 g were placed in drilling fluids 10 0 g available from halliburton energy services as identified in table 2 the sample was allowed to set at room temperature for four days the mixtures were then filtered through a 250 mesh screen and the solid composite microsphere material was allowed to drain for 1 hour the composite microsphere sample was then weighed w f and wt gain was calculated using the formula u2062 u2062 wt u2062 u2062 gain w f 1 0 1 0 u00d7 100 a slurry was prepared by thoroughly mixing glass microspheres acrylate resin and initiators using a mixer obtained from hobart corporation troy ohio model number a120t specific formulation can be found in table 3 the abrasive slurry was mixed in the mixer on low speed using a flat beater style impeller for 30 minutes and heated to a.