Weathering outdoor testing

Another advantage of the amino-resin systems is their applicability to solid wood and wood-composite products. Cedar shingles were the first products treated with this type of fire-retardant system (99, 100, 113, 114). Commercially treated shingles available in the U.S. are based on these systems. Generally, these systems exhibit good durability to outdoor weathering when tested over extended periods (115-17). 

The increase in cellulose content of the weathered wood surface was shown by Browne (50) in work reported by Kalnins (26). Browne compiled analytical data on white pine wood that had been weathered outdoors for 20 years. Results showed that weathering degraded and solubilized lignin. Cellulose appeared to be considerably less affected, except in the top surface layer of the wood. Similar results were obtained with various kinds of wood exposed on a test fence for 30 years. The outer gray layer consistently exhibited very low lignin content (Table II). The lignin content of the brown layer immediately below this layer varied from 40 to 60% of that normally found for fresh nonexposed wood. The composition of inner wood layers only a few millimeters under the outer gray surface was similar to that of... 

Textiles- Tests for colour fastness—Part B03. colour fastness to weathering Outdoor exposure (ISO 105 B03. 1994). 

The destructive effect of the weather varies with geographic location, season, time of day, cloud cover, and exposiue orientation because of variations in the critical weather factors with these conditions. Different weather conditions can also be encoimtered in individual years. Therefore, outdoor tests in one location dining a specific time interval cannot be expected to provide information on either absolute diuabiUties or stability rankings of materials under various service conditions. Tests are commonly carried out in environments that have the most... 

For a product to pass outdoor testing it must be free of any obvious mechanical failure such as peeling or cracking and uniform in appearance, and the average ellipsoid value of weathered samples must be less than or equal to 1.0. 

The accelerated weathering task group members reevaluated their analysis method. They determined that rank-order correlation between the outdoor and accelerated tests was less important than whether the accelerated test method accurately predicted which samples would pass outdoor testing and which would fail. In an effort to determine this, threshold maximum EVs were used in subsequent testing. 

The correlation to outdoor tests for non-white PVC samples was very good, but the white samples did not weather the same as they did in the Arizona outdoor testing (hot and dry). 

Hardcastle HK (2004) Considerations for relating artificial laboratory and natural outdoor weathering durability testing. In Proceedings of the annual technical conference of the society of plastics engineers, Chicago, IL, May 2004... 

Tests in outdoor testing stations have shown that cladding provides an effective protection for many years, whether exposed to weathering or immersed in seawater [29]. The consumption of the cladding avoids corrosion of the underlying core (Figure B.5.5). 

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