Apparent Density Tester for Cellular Plastics

What is the Apparent Density Tester for Cellular Plastics?

An apparent density tester determines the mass per unit volume of rigid or flexible cellular plastic specimens, including any skin, by weighing and measuring the specimen. It is specified for foams where bulk density and true skeleton density are both misleading.

Overview

Apparent density of a cellular plastic is defined as the mass of the specimen divided by its total volume, including pores, voids and any integral skin. Specimens are cut to regular shapes such as cubes or cylinders with defined minimum dimensions, weighed on a balance, and measured with a caliper or by immersion if the surface is sealed. Because foam density can vary across a block, specimens should be taken from defined positions and the sampling plan recorded. The result is used for insulation board, packaging foam and structural foam mouldings, and it differs significantly from both the bulk density of granules and the true density of the polymer skeleton measured by gas pycnometry.

How does it work?

The classical method applies Archimedes' principle: the sample is weighed in air and again while immersed in a liquid of known density, and the difference gives the sample volume. This suits void-free solid specimens and returns density to three or four decimal places. A density gradient column contains a liquid column whose density varies linearly with height, so a small specimen sinks to the level matching its own density and is read against calibrated glass floats, which is useful for very small or thin samples. Gas pycnometry measures the volume of a sample by helium displacement in a calibrated chamber, so it handles powders and porous or irregular material. Bulk and apparent density methods instead measure the mass that fills a defined volume, which is the relevant quantity for granules, powders and cellular plastics.

What are the key features?

• Specimen holder for regular cube or cylinder cutting
• Digital caliper and balance integration
• Support for immersion volume measurement
• Sampling position record for block foam
• Skin-inclusive evaluation option
• Density reported in kg/m³ for board products

What are the technical specifications?

A typical apparent density tester for cellular plastics configuration offers density range of 10–500 kg/m³, specimen size of Cubes from 25 mm, cylinders from 30 mm, balance resolution of 0.01 g, caliper resolution of 0.01 mm, measurement accuracy of ±1% on regular specimens and sampling points per block of Defined by method, typically 5. Values are indicative of the product class; the exact figures for each configuration are confirmed on the quotation and the calibration documents supplied with the instrument.

Which applications is it used for?

The Apparent Density Tester for Cellular Plastics is used in insulation board apparent density verification, packaging foam quality control, structural foam moulding consistency and buoyancy and flotation material checks. Across the wider Density Testing class, laboratories also deploy it for incoming verification of resin density, filler and mineral content estimation in compounds and crystallinity and formulation consistency checks.

Which standards and certifications apply?

Relevant standards and methods include ISO 1183-1, ISO 1183-2, ISO 1183-3, ASTM D792, ASTM D1895, ASTM D1622, ISO 845 and IEC 61010-1. Certification candidates for this model are CE and ISO 9001 manufacturing; each is to be confirmed for the specific configuration before shipment, and certificates are supplied only where they have been issued.

Temperature control is essential because liquid density and sample volume both change with temperature; record the temperature and apply the liquid's density-temperature table. Remove air bubbles from immersed specimens and from pycnometer chambers, as a single trapped bubble changes the volume materially. Weigh the specimen wet mass promptly to limit evaporation and use a covering liquid that does not swell or dissolve the polymer. Calibrate the balance and verify liquid density with a certified glass float or hydrometer at defined intervals. For bulk density, follow the specified funnel, orifice and cup, since changing any of these changes the result.

How do I select the right Apparent Density Tester for Cellular Plastics?

Choose this method for any cellular plastic where the density of the product as used is the required figure, which includes insulation boards, buoyancy materials and packaging foams. Confirm the specimen size and conditioning required by your product standard, and decide whether an integral skin must be included or removed, because that changes the result and must be stated.

How does it compare with other Density Testing variants?

Match the method to the material form. Solid, void-free mouldings and pellets are measured by immersion balances or by density gradient columns when only a small specimen is available. Powders, porous parts and materials that must not contact a liquid are measured by gas pycnometry. Granules, flakes and powders that are handled in bulk are characterised by bulk or apparent density, and rigid cellular plastics by their own apparent density method with a defined specimen. For specification testing, follow the method named in the material standard: ISO 1183 parts and ASTM D792 give different procedures and tolerances for solid plastics, and results from different methods should not be mixed in one data set.