Plastics

Tailor light exposure to the intended application

Targeted UV exposure and broader-spectrum solar simulation represent different loads. The appropriate option depends on the test objective and the agreed procedure. Where relevant, filtering through glass or other covers is also considered.

Alongside the spectrum, irradiance, exposure duration and spatial distribution are defined. For comparable results, the radiation actually reaching the samples must remain traceable. Changes in sample position or luminaire distance are therefore documented.

Key design parameters:

• Relevant wavelength ranges and spectral distribution
• Irradiance at the sample plane
• Size and uniformity of the usable test area
• Radiant exposure and exposure profile over time
• Filtering through glazing or materials positioned in the optical path

Consider temperature, humidity and specimen mounting together

Irradiation is planned together with the other boundary conditions. The actual sample temperature is particularly important, as it can differ from the air temperature. Different colours, material thicknesses and mounting arrangements can lead to different thermal conditions.

If humidity, wetting or additional loading phases form part of the test programme, these are defined within a coordinated sequence. For comparative tests, sample preparation, conditioning and storage between test steps must also remain traceable.

Relevant boundary conditions:

• Specimen temperature and ambient temperature
• Humidity and wetting conditions, where applicable
• Material thickness, specimen geometry and irradiated side
• Mounting and heat transfer through the specimen holder
• Conditioning, interruptions and intermediate storage

Assess changes according to the material’s function

Evaluation is based on the requirements placed on the plastic material. Optical properties may be decisive for a transparent cover, while mechanical or functional characteristics may be the focus for a component subjected to loads.

Measurement methods and evaluation criteria are established in advance and applied after defined exposure stages. Transferring accelerated laboratory results to specific service periods requires validation appropriate to the material and application; test duration alone does not provide a universal conversion factor.

Possible evaluation parameters:

• Colour change, yellowing and gloss
• Transmittance and haze of transparent samples
• Cracks and changes in surface structure
• Mechanical properties determined using agreed test methods
• Function and dimensional stability of selected components

Design irradiation equipment to suit the specimen programme

Whether testing small sample series or larger plastic components, the setup must suit the intended formats and laboratory workflow. Specimen changes, sensor positions and verification measurements are considered during planning.

BF Engineering tailors the irradiation system to the required test area and agreed loading conditions. Interfaces with climate control, temperature monitoring and data acquisition are defined for each project.

Relevant integration considerations:

• Dimensions and number of samples tested simultaneously
• Suitable holders for sheets, films and three-dimensional components
• Electrical supply and heat removal
• Monitoring of irradiation and temperature conditions
• Accessibility for specimen changes, cleaning and maintenance