Textiles

Select illumination to suit the test objective

General UV irradiation does not automatically replace a specified lightfastness test procedure. The required light source and filtering are therefore selected according to the investigation objective and, where applicable, the agreed test specification.

Different conditions may be relevant for outdoor applications, interiors or exposure behind glazing. Alongside the spectrum, irradiance, temperature and the sequence over time are defined. Reference materials are included where required by the selected procedure.

Important exposure parameters:

• Radiation source and spectral requirements
• Filtering suited to the intended application
• Irradiance or the procedure-specific reference parameter
• Temperature and, where applicable, humidity conditions
• Exposure duration and required reference materials

Position flexible materials under defined conditions

Textile specimens require a mounting arrangement that reliably maintains their position during exposure. At the same time, unwanted stretching, folds and shading should be avoided. Mounting is therefore adapted to the material and the area being investigated.

The backing and layer construction can also influence the result. For multilayer products, it is established whether only the outer material or the complete composite will be investigated. Orientation, sampling and any masking are documented.

Relevant specimen mounting considerations:

• Dimensions and orientation of the textile specimen
• Defined tension or low-stress mounting
• Backing and multilayer construction, where applicable
• Flat positioning without folds and unobstructed exposure of the test area
• Identification and masking of designated comparison areas

Align evaluation with the property being investigated

In a lightfastness investigation, the focus is on colour change. Broader ageing investigations may require additional mechanical or functional tests. These are defined as separate evaluation steps.

Measurements before and after exposure are performed under agreed conditions. Demonstrating the UV-protective performance of a textile requires an appropriate measurement and evaluation procedure; an irradiation test alone does not establish a protection classification.

Possible evaluation parameters:

• Colour change according to the selected evaluation procedure
• Differences between exposed and reference areas
• Changes in the surface and condition of the coating
• Mechanical properties according to a separate test plan
• Retention of defined textile product functions

Coordinate the irradiation system with textile sample series

Textile testing can involve numerous small samples and comparison variants. A clearly organised sample arrangement and unambiguous identification make it easier to link exposure with results. Intermediate evaluations and repeated sample changes are also considered in the workflow.

BF Engineering plans the irradiation equipment to suit the required area and intended specimen holders. Requirements for temperature control, monitoring and interfaces are established together with the operator.

Relevant integration considerations:

• Number and format of specimens exposed simultaneously
• Suitable holders for flexible materials
• Accessibility for intermediate evaluations and specimen changes
• Monitoring of the agreed exposure conditions
• Cleaning, maintenance and verification of the irradiation area