Determining Polyethylene Specific Gravity Thresholds for Tariff Entry
Polyethylene tariff entry requires density testing per ISO 1183-1 Method A on annealed plaques, where crossing 0.940 g/cm³ shifts classification from 3901.10 to 3901.20.
Calcium Carbonate Filling Density
Meaning
Material composite properties define the physical behavior of polymer blends containing particulate mineral reinforcements. The calcium carbonate filling density is the resulting specific gravity of a polymer compound that has been loaded with calcium carbonate particles. This value increases in direct proportion to the percentage of mineral filler added to the polymer matrix.
Compounding Influence
Compounding extruders mix mineral filler into the virgin resin to reduce material costs and increase stiffness. The calcium carbonate filling density is determined by the weight ratio of the heavy mineral filler to the lighter polymer resin. A typical resin has a density of about 0.9 grams per cubic centimeter, while the mineral filler density is around 2.7 grams per cubic centimeter.
Adding more filler increases the overall density of the polymer compound.
Molding Performance
Molded part weight and cycle times are affected by the formulation of the polymer. A high calcium carbonate filling density increases the weight of the molded part compared to a part molded from unfilled resin. This increase in weight means the moulder must buy more material by weight to produce the same number of parts.
However, the mineral filler conducts heat faster than the polymer, which allows for faster cooling and shorter cycle times.
Laboratory Measurement
Quality control checks must monitor the uniformity of the compound across the production run. Moulders measure the calcium carbonate filling density to confirm that the compounding step has distributed the filler evenly. If the measured density deviates from the specification sheet, the compounding process has drifted.
This test prevents parts with uneven mechanical properties from reaching the customer. An uneven distribution causes structural failure in the molded part during use.