Understanding the Standard
ISO 4892-3 is a standard that specifies the test conditions duplicating weathering effects on plastic components. This test is done with UV fluorescent lights whereas ISO 4892-2 relies on the use of xenon arc lamps as an illuminating source.
The fluorescent lights discussed in ISO 4892-3 include UVA-340, UVA-351, UVB-313, or a combination of four fluorescent lamps. Accelerated fluorescent UV exposure is essentially used to assess the loss of mechanical properties of the material.
The lamp most recommended in weathering is UVA-340 because its spectral distribution is very similar to the sun, especially at low wavelengths. Conversely, UVA-351 is prescribed to simulate accelerated aging behind a glass window.
Typical Experimental Parameters
Successful exposure testing depends on the precise control of the UV lamp type, irradiance levels, temperature during wetting/exposure phases, and the timing of each part of the cycle.
Pros and Cons of ISO 4892-3
Pros
• UV Degradation Correlation: Strong correlation with material failures experienced in natural outdoor environments.
• Hot Condensation: Delivers continuously reforming condensation at elevated temperatures, providing the most realistic way to accelerate moisture attack.
• Lamp Variety: Offers various lamp types (UVA, UVB) to meet specific testing goals and individual material needs.
• High-Irradiance Cycles: Optional cycles can shorten test times for materials primarily sensitive to light.
Cons
• Realism Limits: Shortwave UVB or very high irradiances may cause some polymers to degrade differently than they would outdoors.
• Aesthetic Coverage: Lack of full-spectrum sunlight may not reproduce all color change effects.
• Excess Spray: Water spray periods of up to 1 hour are often less effective than hot condensation for moisture attack.