Overview
ISO 1068:1975 - Plastics - Homopolymer and copolymer resins of vinyl chloride - Determination of compacted apparent bulk density - specifies a laboratory method to measure the compacted apparent bulk density of PVC resins. The procedure densifies a weighed sample by vibration under defined conditions and calculates the bulk density from the sample mass and the compacted volume (density = m / V). This standard is essential for quality control, material specification, and process optimisation where powder packing and flow behaviour of PVC powders matter.
Key topics and technical requirements
- Scope: Applies to homopolymer and copolymer resins of vinyl chloride (PVC resins) and measures compacted (vibration-densified) apparent bulk density.
- Sample and measurement:
- Use a precision 250 ml graduated glass cylinder, graduated in 2 ml with at least 50 ml non‑graduated top; internal diameter ≈ 38 mm; mass ≈ 220 ± 40 g.
- Weigh the empty cylinder and the cylinder with sample to 0.1 g accuracy. Typical test portion ≈ 100 g.
- Read volumes to the nearest 1 ml.
- Compaction apparatus and conditions:
- Shaking machine: 100–250 falls per minute, fall height 3 ± 0.2 mm.
- Cylinder holder mass: 450 ± 20 g.
- Metallic piston: diameter slightly less than cylinder internal diameter for levelling without compaction.
- Procedure:
- Fill cylinder, place in shaker, perform 1 250 ± 50 cycles, level, read volume.
- Repeat a further 1 250 ± 50 cycles and read again. If readings differ by ≤ 2 ml, take the lower volume; if > 2 ml, continue in 1 250‑cycle increments until two successive readings differ ≤ 2 ml.
- Calculate compacted apparent bulk density as m (g) / V (ml); report in g/ml.
- Instrumentation tolerances and repeatability are specified to ensure comparable results across labs.
Applications and users
- Useful for PVC manufacturers, compounders and masterbatch producers for incoming material inspection, process control (feeding, dosing, blending), and packing/transport decisions.
- Employed by quality control laboratories, independent testing labs, R&D teams and material procurement specialists to specify and compare powder handling properties.
- Helps predict powder behavior in extrusion, molding feed systems and automated dosing equipment where packed bulk density affects throughput and formulation accuracy.
Related standards
- ISO 1068:1975 references the non‑compacted apparent bulk density method in ISO/R 60 (Determination of apparent density of moulding material pourable from a specified funnel).
- Users should consult other PVC test standards and local regulatory test methods for complementary physical and chemical characterisation.
