Copper

Endpoint summary

Additional information

For the physical and chemical properties, a distinction needs to be made between (1) copper in massive form (specific surface area below 0.67 mm2/mg, which is equivalent to spherical particles with diameter above 1 mm), (2) copper in powder/particulate form (specific surface area above 0.67 mm2/mg) and (3) fine coated copper flakes. The composition of these materials is provided in section 1.2.

The physical and chemical properties of copper in massive and powder forms are expected to be the same, except for water solubility. Indeed, chemically, copper massives, have a somewhat higher purity then copper powders (99.9% versus 99.7%). The balancing element is Cu2O. This impurity has little influence on most of the physico-chemical properties. Copper in its metallic form (Cu°) is insoluble because copper needs to be transformed into soluble Cu ions to become soluble. The presence of Cu2O may influence solubility. More importantly, the rate and extent of Cu° transformation (into soluble copper ions) and dissolution into aqueous media depends on the surface area of the material as well as the physico-chemistry of the test media (especially pH). The difference in specific surface area (surface area per unit mass) between copper in massive and in powder form, therefore influence the solubility. Solubility tests in environmental and biological media have therefore been performed on both Cu in massive and powder forms. Transformation-dissolution tests have been performed on various copper forms. These are extensively discussed in chapter 4 of the CSR (Environmental fate properties).

Copper coated flakes on the other hand have a very high reactive surface area. Further, also the coating and the impurities may influence the physical and chemical, ecotoxicological and toxicological properties. Separate physico-chemical tests have therefore been performed with coated copper flakes.

The relevant physico-chemical properties of the materials are summarised below:

 

Table8:Overview of the physico-chemical properties

	Cu metal (massive and powder forms)	Coated copper flakes
Physical state	Solid,copper colour, odourless	Solid,copper colour, odourless
Melting point	1059-1069°C	1057-1058°C
Boiling point	Not applicable	Not applicable
Density	Relative density: 8.78 g. cm^-3at 20 °C	Tap density: 0.47 g/ml at 20°C
Vapour pressure	Not applicable	7.5e-9 Pa (20°C), 1.8e-8 Pa (25°C) and 8.4e-7 Pa (50°C).
Surface tension	Not applicable	Not applicable
Water solubility (H2O)	Insoluble * Stirring and oxidation for 14 days of the copper powder (pH 6.3-7.6) resulted in <1mg dissolved Cu/L	Insoluble * At pH 7-9: <1mg dissolved /L pH 4: 192 mg dissolved Cu /L
Partition coefficient n-octanol/water (log value)	Not applicable	Not applicable
Solubility in organic solvents	Not applicable	Not applicable
Auto-ignition	No auto-ignition	No auto-ignition
Flash point	Not applicable	Not applicable
Flammability	Non flammable	Non flammable
Explosive	Not explosive	Not explosive
Oxidising properties	Not oxidising	Not oxidising
Particle size and specific surface area	From massive forms to particulates and fine powders Copper powder is defined as powders and particulates with specific surface area above 0.67 mm2/mg (equivalent to copper spheres with diameter below 1 mm). .  Copper massive consists of particles with specific surface area below 0.67 mm2/mg (equivalent to copper spheres with diameter above 1 mm). Representative powder samples, characterised with d50 of <50 and 135 µm and specific surface area of 24 - 107 mm2/mg, were used as testing material.	Coated copper flakes have been surface treated and are characterised by a high specific surface area. The granulometric d50 values range between 5 and 100 µm.    A representative sample with a d50of 8-11µm and specific surface area of 2.9 m2/g was used as testing material
Stability in organic solvents and identity of relevant degradation products	Not applicable	Not applicable
Dissociation constant	Not applicable	Not applicable
Viscosity	Not applicable	Not applicable

* Based on information from special solubility tests used for the classification read-across for the environment and for human health. For the environment endpoints, transformation/dissolution tests are carried out- see Chapter 7 of the CSR