Granule, Ground Powder or Sheet: Which Form Survives Your Dosing Line

A converter switching from a 30/60 mesh granule to a 100 mesh ground powder expected faster wet-out and a 4 percent dose reduction. What he got was a feeder that flooded, a dust collector that ran at 90 percent load, and a forming screen that blinded every third shift. The powder was faster, but the line could not carry it. The mistake was choosing the form on absorption data instead of on the machine that had to move it.

Polyacrylate comes as granule, ground powder, and sheet, and each form suits a different kind of equipment. This article compares them on the three things that decide a line: how they feed, how they dust, and how they segregate.

What Each Form Does to a Volumetric Feeder

A 30/60 mesh granule at 0.65 bulk density flows through a 40 mm screw with a fill factor of 85 to 95 percent and holds plus or minus 2 percent over an hour. A 100 mesh powder at 0.55 bulk density floods: the screw fills completely and the feed rate depends on the hopper level rather than the screw speed, giving plus or minus 12 percent until the hopper drops below a third.

Sheet, which is a partially dried polyacrylate film 0.3 to 1.2 mm thick, is not fed at all in the conventional sense. It is slit and cut to width and laid into a product, or ground on the line immediately before use. Where a process wants sheet, it usually wants it because the sheet is the product, not because it feeds well.

Dust, Bridging and Segregation by Form

Dust scales with the fines fraction, and fines scale with the grinding step. A granule carries 1 to 4 percent below 150 microns; a 100 mesh powder carries 25 to 40 percent. That difference shows up as visible dust at every transfer point, a 3 to 5 percent mass loss on a pneumatic line, and a housekeeping burden that is easy to underestimate.

Segregation is the quieter issue. In a hopper, a mixed powder separates by size as it flows: fines migrate to the centre and coarse particles to the wall, so the first and last parts of a hopper discharge are different products. With a granule the size spread is narrow and the effect is small; with a wide powder cut it can be 8 percent in fines between the start and end of a hopper.

Sheet for Clean Lines, Granule for Bulk

Sheet wins where the process needs a fixed dose in a defined area: a thin absorbent layer in a tray, a cable tape, a wound-care dressing. The dose is set by the cutter, not by a feeder, so there is no metering error at all. The cost per kilo is higher because the drying and slitting steps are more complex, typically 20 to 35 percent above granule.

Granule wins in every bulk application: waste solidification, sludge conditioning, spill kits, soil dosing, ice pack filling. It feeds predictably, it resists attrition, and it is the cheapest form per kilo of water absorbed as long as the process gives it 20 seconds to work. Powder wins only where the residence time is genuinely under 10 seconds and the equipment is enclosed.

A 3 kg Trial That Settles the Argument

Before committing to a form change, run 3 kg through the actual feeder at the actual rate for 30 minutes. Weigh the output in three 10-minute increments and calculate the variation. Then run the material through the next process step and measure the result, not the absorption in a beaker.

If the variation is over 5 percent, the form is wrong for the feeder regardless of what the datasheet says. If the downstream result is better but the variation is worse, fix the feeder before changing the product: a 60 degree hopper, a vertical auger with a variable pitch, or a loss-in-weight system will usually recover most of the difference for less than the cost of a reformulation.

Most lines settle on a granule between 20 and 60 mesh, which is the range that feeds well and still wets fast enough for a 30-second mix. The granule, powder and sheet specifications are listed together so the comparison can be made on one page.