Assay Creosote Extraction of Selected Posts from the 1958 Cooperative Test After 50 Years of Exposure as a Ground Contact Preservative

Transcription

1 Assay Creosote Extraction of Selected from the 1958 Cooperative Test After 50 Years of Exposure as a Ground Contact Preservative David A. Webb Creosote Council Valencia, Pennsylvania Stacy A. McKinney Koppers, Inc. Harmarville, Pennsylvania Russel G. Pfeiffer Koppers, Inc. Harmarville, Pennsylvania ABSTRACT This paper presents creosote retention and gas chromatographic data from the southern pine posts, which have been a part of the 1958 Cooperative Project. The data is from selected posts treated with creosotes that closely matched distillates conforming to the American Wood Protection Association (AWPA) Standards for Creosote P1/P13 and Creosote Solution P2. INTRODUCTION The Creosote Cooperative Project was established to determine the effect of different creosote components (as distillates) on the preservative characteristics of this high-temperature coal tar distillate. The original investigators in the project were representatives from Allied Chemical Corporation, Koppers Company, Inc., and Aristech Corporation (formerly U.S. Steel Corporation); subsequently five years after initiation, the Bernuth, Lembcke Co., Inc., joined the project. The paper being presented before this Annual AWPA Meeting here in Savannah is the seventeenth (17) report given to the Association concerning this study the 1958 Cooperative Creosote Project. The most recent paper (Webb, et al. 2009) published as a part of the annual AWPA Proceedings reported results of the 2008 post inspection - 50 years of exposure. The 2008 field inspection was the final one as the exposure site has been closed. The original experimental program consisted of eight (8) test projects: (1) soil-block bioassay, (2) marine-block bioassay, (3) accelerated field exposure: (a) land stakes %-in. square and 28 in. in length, (b) marine waters boards % by 3 by 14 in. (4) simulated land service test with 7-ft. posts, (5) simulated marine service test with 41/2-ft. posts, (6) evaporation studies-3% by 18 in. post sections. 242

2 AMERICAN WOOD PROTECTION ASSOCIATION Original Test Plot for 1958 Cooperative Study Using Southern Pine One of the most significant results from the 1958 Cooperative Project has been the 1978 change in the AWPA, P1/P13 Standard for Coal Tar Creosote for Land and Fresh Water Use. Several changes were made in the distillation specifications of the Standard to reflect the increased wood preservative service life performance that was achieved with an increased concentration level of the high-boiling creosote constituents. The service life of creosote treated wood products is increased with the use of a higher residue; less volatile type of creosote. As shown by creosotes F and G, which have given excellent performance throughout the duration of this 50-year service test. For all practical purposes Creosote G represents AWPA, Standard P1/P13 type creosote and Creosote F represents AWPA, Standard P2 type creosote solution without the addition of coal tar, both creosotes ranked No. 1 in performance at the conclusion to the 50 year southern pine post test. The coal tar distillates used for the project were produced by Allied; the coal tar and petroleum were supplied by Koppers. The coal tar distillates were blended to reflect adjustments in the amount of distillate below 270 C and to also reduce residue below 355 C. These distillation points were characterized by the AWPA E-flask distillation method as given in Standard Al. However, consider that this paper only describes and discusses coal tar distillates F and G. Note for reference purposes Leach reported in 1964 the original physical property information on all eleven of the creosote blended materials as described by the E-flask distillation method. In 1958 the then current AWPA, P1-54 creosote was 41% to 270 C. and 17% residue at 355 C. a low residue; highly volatile creosote this creosote was designated as Creosote A used in the 1958 Cooperative Study. The AWPA Creosote Standard for P1/P13, which as previously indicated changed in 1978 to a higher residue 23% and somewhat lower front-end range of 10 to 40%; with most production usually around 20%. The entire list of creosote physical properties will not be sited in this paper; however, the data is available in the AWPA Proceedings of 1964 with the paper written by C. W. Leach. MATERIALS AND METHODS OF TEST As previously indicated the creosote southern pine posts were installed in 1958 at The Blessing Plantation exposure site in Charleston, South Carolina. For this study purpose only two creosotes G and F were evaluated from those creosote treated post, which containing Creosote G (AWPA, Standard P1/P13) and creosote F (similar to AWPA, Standard P2). No. 414, 436, 438, 439, 443, 446, and 448 represent Creosote G and were originally treated to 9 to 11 pcf by weight. No. 367, 380, and 389 represent Creosote F and were treated to a 7 to 9 pcf retention; while Nos. 375 and 385 retention was 9 to 11 pcf. After pulling the posts, a three foot (3) section was cut using a change saw from each post with the ground-line in the middle of the sample section, and wrapped in plastic bags. Cross section discs one inch thick were cut on a bandsaw and, before analysis, then further reduced into three zones 0 to ½ inch, ½ to 1-inch, and 1 to 2-inches. 243

3 AMERICAN WOOD PROTECTION ASSOCIATION Wrapping Post Sample Sections Creosote Assay Extraction Samples for extraction were obtained by splitting each zone radially and along the grain into splints approximately one-eighth inch thick. Six 12 to 15-gram samples prepared for each zone were extracted using the A6 method (AWPA Standards 1986), including a 5-hour refluxing time in toluene. Moisture and retention data were developed for all four zones in each section and the extracts in toluene saved for later qualitative analysis using the gas chromatograph. Calculated retentions shown in Table 1 are based on oven dry extracted weight of wood and volume of wood as estimated by using 32 pounds per cubic foot (pcf) density for southern yellow pine (.5126 grams per cubic centimeter). All samples were sapwood and entirely penetrated with preservative. AWPA, A6 Extraction Method Being Performed by Rus Pfeiffer 244

4 Table 1. Summary of Retention Data in Pounds per Cubic Foot (pcf) Section Post #. Creosote Assay Zone 0 to 0.5 inches 0.5 to 1.0 inches 1.0 to 1.5 inches Above Ground 367 F* All F** All G** All Below Ground 367 F* All F** All G** All Creosote F* Creosote F** Creosote G** treater originally to 7 to 9 pcf 9 to 11 pcf -- original treatment 9 to 11 pcf -- original treatment 245

5 Gas Chromatography Prep A sample of the Extracted solution was filtered through a 0.45 micron syringe filter, placed into a two ml sample vial and positioned into the sample tray for analysis. The toluene used in the extraction is a suitable solvent for the Gas Chromatography (GC) method therefore there is no need for the addition of other solvents. Upon analysis, the sample was injected into the GC with a SPB-5 capillary column supplied by Supelco or an equivalent substitute, equipped with a split/splitless injection system, the components being detected with a Flame Ionization Detector, and the data integrated by Perkin-Elmer Turbochrome software. Included with the sample set, a certified standard was analyzed to verify the retention times of the components with its results being compared to the Certificate of Analysis to verify that the equipment was functioning properly. The following are the chromatography conditions that were used, with the results reported in Area %: Injection Temp.: 300 C (split set 30:1) Detection Temp.: 320 C Initial Temp. 40 C for 5 minutes Oven Profile: 5.0 C/minute to 165 C, Ramp 1 hold for 5 minutes 10.0 C/minute to Ramp C, hold for 10 minutes Helium was used as the carrier gas with the pressure set constant at approximately 10.9 psig. DISCUSSION OF RESULTS This study of creosote residuals is not intended to give specific conclusive evidence about the quality or quantity of preservative after 50 years of exposure. However, generalizations can be made using this information which may be useful when consideration is given to reasons for which changes were made the creosote specifications. As previously indicated in 1978, the P1/P13 creosote specification was change based entirely on field inspection data. The higher residue and less volatile (creosote G ) gave significantly better performance than the then current AWPA Creosote P1/P13 Standard represented by creosote distillate A. Toluene extractable creosote as shown by retention data in Table 1 was concentrated in the outer zone in both above and below groundline. With both Creosotes F and G, the concentration of creosote components was in the outer half inch zone. In addition, as expected the concentration of creosote was in the below groundline section of the posts. This supports the theory of creosote preservative migration into the lower portions of the post, along with evaporation from upper weathered exposured areas of the posts. Toluene extractable creosote was from post 367 were analyzed using gas chromatography and these data shown in Table 2. Once again the data supports the fact that higher residue distillates creosote give more satisfactory service life for treated wood products. Change in AWPA Specification in 1978 to make creosote less volatile was the proper decision. Compare the first five low boiling compounds indane, the three naphthalenes, and biphenyl which were not even detected in the 50 year aged creosote post treated with Creosote F, with the current P2 creosote, in which all five of the these compounds were detected. However, the authors are suggested that these low boiling compounds be further reduced as this could have an affect on viscosity and the ability of creosote to penetrate wood during pressure treatment. 246

6 Table 2. Gas Chromatograph Analyses of 50 Year Post Post No. 367 (below ground)* Creosote Component Creosote F Current P2 Creosote Indane 0% 1.5% Naphthalene methyl naphthalene methyl naphthalene Bipheny Acenaphthene Dibenzofuran Fluorene Phenanthrene Anthracene Carbazole Fluoranthene Pyrene *Assay zone zero to 1.5 inches CONCLUSIONS There are several valid conclusions that can be drawn for creosote as a wood preservative based on data gathered in the 1958 cooperative study: The service life of creosote treated wood products is increased with the use of a higher residue; less volatile type of creosote. Creosote F & G, which have given excellent performance throughout the duration of this 50-year service test. For all practical purposes Creosote F represents AWPA, Standard P2 type creosote and Creosote G represents AWPA, Standard P1/P13 type creosote. Both types of creosote have performed similar in the southern pine throughout this study. There is a very significant conclusion that can be reached from this long-term test on creosote. Based on short-term soil-block test results, one can conclude that creosote formulations F and G will give improved service life as compared to high volatile creosotes such as creosote A. It is thus possible to establish, in this instance with creosote, that the short-term soil-block test could predict the long-term perform of creosote treated wood products. This comparative data with soil blocks and posts is given in Table 3. ACKNOWLEDGMENT This 50-year study yielded valuable data on the long term performance of creosote as a ground contact wood preservative. The authors wish to acknowledge the assistance of all the original companies, who had the foresight to initiate this study on creosote. Many individuals played an important role while this 50- year project was evolving. Most are listed in the literature cited section of this paper as authors of the papers various papers cited. However, a few deserve special mention Randy Baileys gave a paper, published in the AWPA Proceedings 1987, which gave GC data on creosote extractions from these test posts after 26-years in test. This was ground breaking work. 247

7 In addition the authors appreciate Billy Cairns gas chromatograph laboratory work with the creosote samples. Jim Gauntt, executive director of the Railway Tie Association, believed in the continuation of the 1958 Cooperative Project and provided financial support for several of the last inspections. Table 3. Comparative Rank of Creosotes in Soil Block, Stakes (Empty Cell) and 7 Ft at 6 PCF Creosote Retention 3/4 inch Rank Soil Block Stakes 20 Years 25 Years 30 Years 35 Years 43 Years 50 Years 1 F F (57) G (96) G (92) G (94) G (81) F-G (63) 2 G D-G (30) C-F (91) F (90) F (89) F (78) -- 3 D C (85) C (88) C (73) C (51) 4 C C (22) D (76) D (63) D (54) D (31) D (23) 5 A A (20) A (29) A (16) A (3) A (0) -- () Indicates average index of condition in the 5.0 to 6.9 creosote retention range. LITERATURE CITED 1. AWPA Method for the Determination of Oil-Type Preservative and Water in Wood. American Wood Protection Association Standard A6-09. Standard Method for Determination of Retention of Oil-Type Preservatives from Small Samples, Birmingham, AL. 2. Baileys, R. T., and D. A. Webb, Cooperative Creosote Project XII: An Analysis of Creosotes from after 26 Years in Test. 3. Colley, R. H The Practical Meaning of Preservative Evaluation Tests. AWPA Proceedings 66: Colley, R. H., H. J. Fry, W. T. Henry, and D. A. Webb Cooperative Creosote Project-X: Field Tests with Stakes and after 20 Years in Tests. AWPA Proceedings 76: Leach, C. W Cooperative Creosote Project: I. Laboratory Soil-Block Tests. AWPA Proceedings 60: Webb, D. A., R. H. Colley, R. F. Fox, and W. T. Henry Cooperative Creosote Project-XI: Field Tests with after 25 Years in Test. AWPA Proceedings 80: Webb, D. A., and R. T. Baileys. 1995, 1958 Cooperative Creosote Project XIV: 35 Years of Field Exposure with. AWPA Proceedings 91: Webb, D. A., R. T. Baileys, G. P. Merrick, and R. G. Pfeiffer. 2002, Creosote 43 Year of Experience as a Ground Contact Preservative, AWPA Proceedings 98: Webb, D. A., R. F. Fox, and R. G. Pfeiffer. 2009, Creosote Final Inspection of the 1958 Cooperative Test After 50 Years of Exposure as a Ground Contact Preservative 248