Cover Image

Not for Sale

View/Hide Left Panel
Click for next page ( 14

The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement

Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 13
13 Table 1. FL-DOT FM 5-573 test conditions. However, this test will not be able to evaluate manufacturing stresses like the FL-DOT test. A test that still holds promise Test Temp. Applied (C) Stress (psi) for that purpose is the ring stress-crack test (7). It could not 70 650 be used during this project because of the large variability in 80 650,450 pipe-wall thicknesses measured. However, there may be a way to modify it, or test multiple sections from a full diameter that would result in a valuable test for evaluating pipes containing Only the thinnest part of the specimen experiences the full recycled HDPE. More time and funding would be required to stress. develop the concept into a valuable quality control (QC) or There is significant sample preparation stresses imparted, qualification test. especially in larger diameters. Similarly, if the FL-DOT junction test could be performed on There are significant edge effects from the cutting die, wider test specimens, the results would be more meaningful. especially on larger diameters. However, this would require stress-crack testing devices that were larger to accommodate a wider specimen and greater Test method FM 5-573 calls for the test to be run under three loads. The FL-DOT junction test with a Type IV (as defined by different conditions of stress and temperature in deionized ASTM D638) specimen can be performed on most conven- tional stress-crack frames. (D.I.) water. These are shown in Table 1. Five replicates under These tests will be evaluated for use as a tool for predicting each set of conditions are tested. the long-term stress-crack (Stage II) resistance of pipe-resin The three sets of results are then analyzed by the RPM, which formulations containing recycled PE. has been used for many years on pressure pipe. The test protocol also allows the tests to be terminated when they reach the following conditions: The Long-Term Oxidation (Stage III) Resistance Terminate at 110 hours for 80C/650 psi. At very low service stresses and after very long times, a PE Terminate at 430 hours for 80C/450 psi. part can become oxidized and fail by many cracks forming Terminate at 500 hours for 70C/650 psi. in a short period of time. This failure mechanism is known, especially in exposed applications where UV initiates oxidation These times were determined with the use of an average or in potable water applications where higher concentrations slope of a number of stress-crack tests and POP. of chlorine can initiate oxidation. However, for typical buried pipe applications the rate of oxidation and the extraction The BFF Test of long-term antioxidants are very, very slow. Over the past 20 years, accelerated aging results on PE stabilized with com- The BFF test uses a specimen, cut from a plaque, about mon additive packages such as Irganox 1010* and Irgaphos the size of the BAM specimen (4 in. l 0.5 in. w). The test is 168 have suggested that the service lifetime is easily in the performed under the conditions of the FL-DOT durability hundreds of years. Therefore, it is believed that as long as there protocol (80C/650 psi, 80C/450 psi, 70C/650 psi) in D.I. is some basic stabilization, Stage III oxidation is not likely to water with a dumbbell shaped test specimen in which the ends occur in typical buried pipe applications. Specifications for are twice as thick as the center to reduce failures at the grips. pipe resins containing recycled content can specifically state The advantages of this test for testing pipe containing recycled that a particular stabilizer package be used. This can be verified HDPE are with an OIT test. The OIT test cannot identify specific additives, but it can measure concentration if 1,010 and 168 are used. The exposed surface area is about 5 times larger than the These ingredients are two of the least expensive stabilizers FL-DOT specimen. for PE. When used at levels of 1,000 ppm Irganox 1010 and The thickness is controlled so the stress is even throughout the specimen. The specimen thickness (0.0040 in. to 0.0045 in.) means *The Transportation Research Board, the National Research Council, flaws will have a greater effect than on thicker specimens. the Federal Highway Administration, the American Association of State A wider and thinner test specimen means less edge and Highway and Transportation Officials, and the individual states partic- ipating in the National Cooperative Highway Research Program do not cutting die effects. endorse products or manufacturers. Trade or manufacturers' names It is sensitive to contaminants found in PCR HDPE, like appear herein solely because they are considered essential to the clarity particulates. and completeness of the project reporting.