Natural Solar Exposure Testing for Durable Plastics
ISO 877-2 is an internationally-recognized standard that provides guidance on exposing plastic materials to real-world solar radiation. It is the second part of a three-part series (ISO 877-1, ISO 877-3) and focuses specifically on direct weathering and exposure behind window glass. By utilizing standardized outdoor exposure methods, manufacturers can accurately assess property changes over time, aiding in the development of more durable and weather-resistant products.
Test Parameters
Exposure Orientation
- Aspect and Direction: Test racks must face the equator to capture maximum solar radiation.
- Tilt Angles: Common configurations include 5° (to prevent water pooling) or 45° (for high solar exposure and comparison with historical data). Note the angle is with respect to the horizontal.
- Latitude Adjustments: For sites at latitudes greater than 20°, the tilt should be adjusted to the site latitude minus 5° to 10°
- Ground Clearance: Specimens must be mounted at least 0.5 m above the ground or any other obstruction to avoid interference.
- Shadow Avoidance: Sites must be situated so that no shadows fall on specimens when the sun's elevation is 20° or higher.
Mechanical and Material Requirements
- Corrosion Resistance: All fixture materials, such as stainless steel or specific aluminum alloys (6061T6 and 6063T6), must resist corrosion without surface treatments.
- Stress-Free Mounting: Holders must apply minimal stress to specimens, allowing for natural movement like shrinkage, expansion, or warping.
Method A: Direct Weather Exposure
- Material Exposure: Specimens are open to all climatic elements, including rain and wind.
- Climatic Recording: Testing requires the continuous monitoring of solar radiant exposure and local climatic factors to provide context for the observed property changes. Q-Lab provides weather data from its Florida, Arizona, and Ohio sites.
Method B: Under Glass Exposure
- Ventilation Gap: A distance of at least 75 mm (but no more than 300 mm) is required between the glass cover and the specimen surface to allow for adequate airflow.
- Glass Specifications: The glass must be non-laminated, uniformly transparent flat glass with a thickness between 2.0 mm and 3.2 mm. (Refer to ASTM G24 for guidance on glass pre-aging, routine maintenance, and lifetime of glass)
- Transmission Monitoring: Glass must be replaced if its transmission at 320 nm drops to 80% or less of its original value, or at least every five years if not measured.
- Radiant Exposure: If measuring radiant exposure, the radiometer must be positioned behind the glass, parallel to the specimen rack at a distance of 75 mm.
Exposure Stages and Measurement
- Duration: Exposure is typically specified in months or years
- Radiometry: Radiometers must be mounted 75 mm behind the glass and parallel to the specimen rack.
Why Test to ISO 877-2
ISO 877-2 allows manufacturers to asses material performance against global quality standards. This standard offers a framework for assessing the long-term durability of plastics in benchmark outdoor weathering locations. By utilizing these exposure methods, manufacturers can make data-driven decisions that strengthen product life cycles and maintain material integrity in the field.
Pros and Cons of ISO 877-2
- Realistic Testing Conditions
- Natural outdoor testing provides the most accurate and realistic testing environment - the true answer to make sure your accelerated laboratory tests are appropriate
- Versatile Testing Methods
- ISO 877-2 provides two different testing methods (direct exposure, and under glass), allowing for the simulation of both outdoor and indoor/automotive environments
- Internationally Recognized Standard
- The standard specifies exact requirements for apparatus, specimen mounting, climatic measurements, and site selection, which helps minimize variables between OEM testing programs
- Inexpensive
- Like all outdoor testing, ISO 877-2 is an inexpensive option that provides valuable benchmark data
- Flexible configurations
- By allowing different exposure angles, glass types, and mounting options, ISO 87702 allows users to select the right exposure type for their applications
- Unpredictable variability
- While exposing materials to natural outdoor elements is crucial to a successful testing program, there are many variables that can impact the results. It's important to constantly monitor specimens to fully understand any property loss on materials.
- Long testing duration for durable materials
- Although outdoor testing gives true results regarding in-service performance, some users may prefer accelerated testing for faster results and control of test parameters, though that should always be validated with outdoor data
How Q-Lab Can Help
Q-Lab offers outdoor exposure testing programs at our internationally-recognized, ISO 17025-accredited benchmark locations in Florida and Arizona. Weathering exposures at these sites are not only realistic; they also could be considered a form of accelerated weathering testing (depending on where the product will be used outdoors) and are the best way to verify laboratory test results. Q-Lab also provides all users with climate data to enhance interpretation of data collected during outdoor exposures. See our Outdoor Testing brochure for more information on these sites and our Testing Services brochure to learn about our full range of weathering testing services.
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