Overview
ISO 22498:2005 specifies a mechanical sieving method for determining the particle size distribution of vinyl chloride homopolymer and copolymer resins (PVC resins). The standard covers sample preparation, apparatus, test procedure and calculation of results so that outcomes can be reported either as the percentage retained on each sieve or as a single mean particle size for the test sample. The method is intended for routine quality control and material characterization and is not recommended for sieve meshes smaller than 0.038 mm.
Key topics and requirements
- Test sample: 20.0 g ± 0.1 g of resin; anti‑static agent (e.g., aluminium oxide or carbon black) may be added up to 0.1% by mass.
- Sieves and apparatus:
- Nominal 200 mm diameter sieves conforming to ISO 565; recommended mesh sizes include 0.425, 0.250, 0.150, 0.106, 0.075 and 0.063 mm as a minimum.
- Mechanical sieve shaker delivering a vertical motion with a “tap” at each stroke; tapping rate 150 ± 15 taps/min; timer set to 13 min ± 2 min.
- Balances: precision to ±0.001 g and ±0.1 g for weighing sieves/pans and retained resin.
- Other items: soft‑bristle brush, vacuum cleaner for cleaning, rubber blocks (approx. 40×10×15 mm, Shore A hardness ~70–80).
- Procedure essentials:
- Clean and inspect sieves, weigh empty sieves and pans, assemble stack in ascending order of mesh size (largest aperture on top).
- Run two determinations per sample, weigh retained resin on each sieve and the pan.
- Calculations:
- Compute average mass retained on each sieve (mean of two determinations) and express as percentage of the test sample.
- For mean particle size, compute an average particle size for adjacent sieve pairs (midpoint of adjacent mesh sizes) and calculate a weighted mean using the percentage retained on the smaller aperture in each pair. Ignore material retained on the largest sieve and in the pan for this mean-size calculation.
- Cumulative retention across the stack and pan must exceed 99% or the test must be repeated.
- Precision: Interlaboratory precision data are not available (precision unknown).
Applications and users
- Typical users: PVC resin manufacturers, QC/analytical laboratories, compounders, material suppliers, and R&D teams.
- Practical uses:
- Routine quality control and acceptance testing of vinyl chloride homopolymer and copolymer resins.
- Specification compliance and supplier qualification.
- Process optimization in extrusion, compounding and molding - particle size distribution affects flow, dispersion and final product properties.
- Batch-to-batch consistency checks and troubleshooting (e.g., dust levels, fines content).
- Benefits: Standardized, replicable mechanical sieving provides clear, comparable particle‑size data for material selection and process control.
Related standards
- ISO 565 - Test sieves (nominal opening sizes and construction)
- ISO 868 - Plastics - Shore hardness (used for rubber block specification)
- Prepared by ISO/TC 61/SC 9 (thermoplastic materials)
Keywords: ISO 22498:2005, particle size determination, mechanical sieving, vinyl chloride homopolymer, copolymer resins, sieve shaker, mean particle size, particle size distribution, PVC resin quality control.