Carbon Black | EUROLAB

What Is Carbon Black Content?

Carbon black analysis answers two separate questions. The first is QUANTITY: the sample is pyrolysed in an inert atmosphere, the polymer decomposes, and the remaining carbon black is weighed (ISO 6964). The second is DISPERSION: thin sections are examined under a microscope and graded for agglomeration (ISO 18553).

Purpose of Carbon Black Content

The purpose is to verify the UV protection of polyolefin products used outdoors. Carbon black is the fundamental additive enabling polyethylene pipes to last decades outdoors, but it only works if present in sufficient quantity AND well dispersed.

Which Products Is Carbon Black Content Applied To?

Polyethylene water and natural gas pipes
Geomembrane and geotextile products
Polyolefin parts used outdoors
Cable sheaths
Agricultural film products

In Which Sectors Is Carbon Black Content Used?

PlasticsPackagingAutomotiveElectronicsConstruction

Standards Related to Carbon Black Content

ISO 6964 (carbon black content in polyolefin pipes and fittings — pyrolysis)
ISO 18553 (assessment of pigment or carbon black dispersion in polyolefins)
ASTM D1603 (carbon black content in polyolefins)
EN 12201 / EN 1555 (PE water and gas pipes — product standards)

Carbon Black Content Conditions

Quantity method: Pyrolysis and residue weighing under inert gas
Distribution method: Microscopic examination and grading of thin sections
Specimen: It is taken from the pipe wall in a position in accordance with the standard.
Section: Thin sections taken with a microtome

Equipment for Carbon Black Content

Pyrolysis furnace and nitrogen supply system
Analytical balance and desiccator
Microtome
Light microscope and image analysis system
Comparison grades (ISO 18553 templates)

Sample Requirements for Carbon Black Content

The sample must be taken so as to represent the batch or production run.
Sample description, material type, and production direction if any, must be stated.
The standard to be applied and any customer specification must be provided together with the sample.
The test may be destructive; the required number of samples must be confirmed in advance.
Surfaces that will be tested must be protected during transport.

Duration of Carbon Black Content

Pyrolysis and weighing are completed within one working day; dispersion examination takes additional time together with section preparation.

Carbon Black Content Procedure

1The sample is taken from the pipe wall in accordance with the standard.
2For quantity, the sample is weighed and placed in the pyrolysis furnace.
3Heated under inert gas until the polymer decomposes.
4The residue is cooled in a desiccator and weighed.
5Thin sections are taken with a microtome for dispersion.
6Sections are examined under the microscope and agglomerate sizes assessed.
7Quantity percentage and dispersion grade are reported together.

Carbon Black Content Acceptance Criteria

The method standard defines how the test is performed, not what the result must be. The acceptance limit comes from the material or product standard, the customer specification, or the relevant regulation; this page therefore does not give a numerical limit.

Evaluation of Results

The result is compared against the requirements given by the product standard (e.g. EN 12201) for carbon black content and dispersion grade. Both conditions must be met: sufficient quantity but poorly dispersed carbon black creates weak points around agglomerates.

Carbon Black Content Report

Sample description, material/product information, and batch number if any
Sample preparation method and conditioning conditions
Standard and test conditions applied
Instrument used and calibration status
Measurement results and units
Measurement uncertainty (if requested)
A statement that the result applies only to the specimen submitted for testing

Accreditation

EUROLAB holds internationally recognised accreditation obtained from accreditation bodies party to the IAF and ILAC multilateral recognition arrangements, under ISO/IEC 17025 for laboratory testing, ISO/IEC 17020 for inspection and surveillance, and ISO/IEC 17021-1 and ISO/IEC 17065 for system and product certification. This chain ensures the reports and certificates issued are accepted worldwide.

Whether this test can be offered within accredited scope depends on your product and the standard applied; since accreditation is method-based, the scope is confirmed in writing at the quotation stage.

Scope and authorisations

Related Regulations

Harmonised standards applied according to the product family
EU 765/2008 (market surveillance and accreditation framework)
Relevant product regulations and customer specifications

Plastics Testing — What Does This Testing Field Cover?

The section below describes the field that the Carbon Black Content test belongs to; the conditions and acceptance criteria of this particular test are given in the sections above. The scope specific to your product is confirmed in writing at the quotation stage.

Plastics testing determines the mechanical, thermal and burning behaviour of a polymer material. Unlike metals, plastics are VISCOELASTIC: their behaviour depends on loading rate, temperature and moisture. The same material therefore gives different results under different conditions, and the test conditions are an inseparable part of the result.

The practical consequence of viscoelasticity is this: a plastic part continues to deform over time under a constant load (creep) and the stress it carries at constant deformation falls over time (stress relaxation). A screwed joint loosens, a clamp loses its clamping force, a shelf sags over time. A short-term tensile test does not show this behaviour; a long-term test or an accelerated model is needed.

Thermal behaviour is the second main axis. Melt flow rate indicates the processability of the material and lot-to-lot consistency; heat deflection temperature and the Vicat softening point give a rough limit for service temperature. Thermal analysis (DSC, TGA, DMA) reveals the identity of the material: glass transition temperature, melting behaviour, crystallinity, filler content and decomposition temperature.

Burning behaviour is the third axis and ties directly into product standards. The UL 94 class and the limiting oxygen index are written into the material data sheet; a particular class is required for the housing of an electrical appliance, while a different classification system applies to a construction product.

Ageing is the most frequently skipped part of the field. Plastics degrade under UV, heat, moisture and oxygen: colour changes, the surface cracks, impact strength falls. For a part intended for outdoor use, what matters is not its values on day one but its values after ageing. Xenon arc and fluorescent UV equipment accelerate this degradation and allow comparison.

The output of this family is usually written into the material data sheet, and product standards refer to that sheet. But there can be a difference between the data sheet value and the behaviour of the actual part: orientation formed during moulding, weld lines and internal stresses make the part behave differently from the specimen.

The use of recycled content has added a new question to the field. Recycled resin varies from lot to lot; mechanical properties, colour and burning behaviour can shift between batches. For a manufacturer using recycled material, incoming material control is therefore not a choice but a necessity.

Method groups in this field

Mechanical
Tension, compression, bending, Charpy and Izod impact, hardness (Shore), creep and environmental stress cracking.
Thermal
Melt flow index (MFI), heat deflection temperature (HDT), Vicat softening temperature, linear thermal expansion.
Thermal analysis
Transition temperatures and crystallinity by DSC, composition and decomposition by TGA, dynamic mechanical behaviour by DMA.
Burning
UL 94 classification, limiting oxygen index (LOI), glow wire and needle flame tests.
Ageing
Accelerated ageing by xenon arc and fluorescent UV, hot air ageing, humidity and condensation.
Physical
Density, water absorption, ash content, gas and water vapour permeability of films and sheets.

Commonly confused in this field

A plastics result without a stated test rate and temperature cannot be interpreted; viscoelastic behaviour depends on these parameters.
A specimen result does not transfer directly to the actual part; moulding orientation and weld lines are decisive.
HDT and Vicat values are NOT service temperatures; they are a rough indication of an upper limit and do not apply under load.
The UL 94 class depends on thickness; a different wall thickness requires re-verification.
For moisture-absorbing polymers (such as polyamide), results are misleading unless conditioning is carried out.
ASTM D638 and ISO 527 results are not directly equivalent; the specimen geometries and rate definitions differ.

Which decisions these results support

Material selection and supplier approval
Meeting the flammability and thermal requirements of the product standard
Verifying the use of recycled content and lot control
Moulding process control and lot consistency
Demonstrating ageing resistance for outdoor use

Related Tests

Frequently Asked Questions About Carbon Black Content

If quantity is sufficient, is dispersion assessment still needed?

Yes. Agglomerated carbon black leaves UV protection uneven and creates stress concentration points. Product standards therefore require both together.

Is it applied to coloured products too?

Carbon black analysis is for black products. UV protection in coloured polyolefins is provided by different additives and assessed by other methods.