Plastic material prepared from commercial low density polyethylene (LDPE). obtained from DSM Resolve, Galeen, The Netherlands.
The CRM was prepared from a low-density polyethylene (LDPE) granulate spiked with inorganic pigments (As2O3, Green 36, ZnS/CdS, Green 7, Cr2O3, PbCrO4/PbSO4, HgS, Sb2O3, SnO2). Most frequent use of the target elements is as colourant, i.e. in the form of pigments. Therefore, inorganic pigments were added to achieve the target contents for the various elements. Due to the nature of the production process, these pigments cannot be present in the initial polymerisation process but have to be blended into the final LDPE granulate.
Pigments were ground to particle sizes < 1 μm if necessary. For each material, a master batch of a higher element concentration was produced by mixing with PE powder in a nail mill and subsequent extrusion. The granulate obtained was mixed, blended with blank LDPE to yield the desired element concentrations and extruded. The granulate from this step was mixed again and extruded a second time.
Certification of the CRM included testing of the homogeneity and stability of the material as well as the characterisation using an intercomparison approach.
The new CRMs have been certified for their content of As, Br, Cd, Cl, Cr, Hg, Pb, S, Sb and indicative values have been established for Sn and Zn. Additional information about acid digestible Cr is given.
These CRMs are intended for use in quality assurance of measurements of elements in polymers and related matrices.
keywords: Industrial material, Polymers, Trace elements, Heavy metals