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T&D > Programs Areas > Inventory & Monitoring > String Degradability Program Areas
String & Flagging Degradability


A total of four types of hip chain line and 17 types of flagging tape were chosen from Ben Meadows and Forestry Suppliers. The tapes varied by texture, color, and material, with an emphasis on brighter colors. Testing methods are similar to those recommended by ASTM International. The tapes were cut into five inch lengths and the line was 12 inches, as indicated by ASTM D 882-02 and ASTM 2256-02. A pair of samples were tested at each level of exposure – new (control test), 126 hours, and 500 hours.The samples were then tested for breaking strength.

Caveats - It is important to take note of a few points regarding these testing procedures. These tests investigate degradability. Degradability is not the same as biodegradability. Degradability refers to the break down of material due to physical influences, such as UV light. Biodegradability refers to the break down of material through biological means, like bacteria. These tests were conducted a single roll of each type of flagging or string. Variations may exist among other samples due to manufacturing practices or storage conditions. The intent of this work is to provide a relative idea regarding the degradation of these field materials.

Weather acceleration was conducted in a Q-Sun Xenon Test Chamber Model Xe-3-HS. This chamber has three Xenon Arc bulbs with a specific filter. There are several filters available for the Q-Sun; this test employed a filter equivalent to noon, summer sunlight, which was the Daylight – Q. With the bulbs and the filter in place, the exposure to any test sample would be an accelerated form of degradation compared to natural sunlight. While no actual timeframe for accelerated exposure can be compared to natural conditions, the manufacturer of the Xenon Test Chamber informed us that typical testing times were 500 and 1000 hours and increasing by increments of 500. The 500 hour test created considerable deterioration of some materials, so an intermediate test of 126 hours was also used.

Photo of the face of the Xenon Test Chamber.
Face of Xenon Test Chamber.

Xenon Test Chamber
Xenon Test Chamber.

The test performed is Cycle 1 in ASTM G 155-05, also known as the "102/18" cycle and parameters such as humidity, irradiance, wavelength and temperature were set and controlled. The first 102 minutes exposed the samples to an equivalence of noon summer sunlight and the next 18 minutes had the same exposure just with a 5 second spray of deionized water every minute. This is the typical exposure test cycle that is used when testing nonmetallic materials in a Xenon Test Chamber, according to ASTM G 155-05.

With the samples in the chamber, aluminum frames were used to retain the test samples. These frames expose 3 inches of each flagging sample and at least 10 inches of line.

Aluminum Frames

Aluminum Frames with Samples

For the second part of the test, a Tinius Olsen Testing Machine was used to determine the breaking force required for each sample. Aluminum clamps were constructed to accommodate ASTM D 882-02 and foam tape was used to eliminate breakage and slippage. The ASTM requires samples to break in 20 seconds +/- 2 seconds. Two rates of separation were determined for the 17 types of flagging tape. There were four fiber type flagging samples, know as biodegradable flagging; these samples required a slower test rate then all the other samples. With the Tinius Olsen at the slow setting, the rate of separation was 0.02 in/min. For the rest of the samples, the rate of separation was dialed in at 0.2 in/min. The sample of the each tape tested was two inches in length. While the string samples were 10 inches long. Due to issues with the clamping mechanism, the hip chain line was tested manually using a Pesola Medio-Line scale.

Tinius Olsen with Clamps

The Tinius Olsen output and scale readings were compiled, and the paired breaking strengths were averaged and assembled into the charts provided.