Diffusion Limited Oxidation (DLO) Modeling of Tires During Oven Aging

This report is the sixth in a series of scientific reports intended to provide an understanding of the chemical reactions responsible for the degradation of light vehicle tires during on-vehicle service. The report series was used to guide the agency’s development of a laboratory-based accelerated service life test for light vehicle tires (i.e., “tire aging test”). Oven aging tires at 55 to 65°C, while pressurized with an oxygen-rich inflation gas, has been identified as the primary candidate for a tire aging test. However, the agency was cautioned that the level of oxygen required for reactions within the tire rubber at the higher oven temperatures could exceed the supply of the oxygen diffusing to the rubber components, resulting in an effect termed Diffusion Limited Oxidation (DLO). DLO could result in the outermost layers of the tires experiencing anaerobic (without oxygen) reactions that are not representative of what light vehicle tires experience during normal service. To explore these concerns, the oxidation rates in the shoulder region of twenty four tire models were predicted at two temperatures (55°C and 65°C) using a computer model. To confirm simulation results, chemical and physical property data was taken from the shoulder region of the tire models before and after actual oven aging at the same conditions as were simulated by the computer model. The computer simulations predicted that none of the tires would experience DLO at 55°C oven aging, and conversely that all of the shoulder regions would experience some DLO at 65°C, especially in the tread of light truck tires. To explore these results, tires that had high and low levels of predicted DLO were compared using two measures. The first measure, the level of fixed oxygen in the tread compound, showed no indication of the predicted DLO after aging at 65°C for eight weeks. The second measure, modulus profile of the tread shoulder, also showed no indication of the predicted DLO. Therefore, the 65°C oven aging temperature is not expected to significantly limit oxidation in any component of the tire shoulder region. A probable reason for the significant over-prediction of DLO in these tires is likely the inability of the 1-D computer model to account for the multi-dimensional wicking of oxygen, especially at elevated temperatures, throughout the carcass, steel belt layers, and, if present, the nylon plies of a tire.

• Record URL:
  http://www.nhtsa.gov/DOT/NHTSA/NVS/Vehicle%20Research%20&%20Test%20Center%20(VRTC)/ca/811266.pdf
• 
• Corporate Authors:

  Akron Rubber Development Laboratory, Incorporated

  2887 Gilchrist Road
  Akron, OH  United States  44305

  Transportation Research Center, Incorporated

  P.O. Box B-37, 10820 State Route 347
  East Liberty, OH  United States  43319-0337

  National Highway Traffic Safety Administration

  1200 New Jersey Avenue, SE
  Washington, DC  United States  20590
• Authors:
  • Terrill, Edward R
  • Centea, Mark
  • Pannikottu, Abraham
  • Karmarkar, Uday
  • Evans, Larry R
  • MacIsaac Jr, James D
• Publication Date: 2010-2

Language

• English

Media Info

• Media Type: Web
• Edition: Final Report
• Features: Figures; References; Tables;
• Pagination: 62p

Subject/Index Terms

• TRT Terms: Aging (Materials); Light vehicles; Ovens; Oxidation; Rubber; Service life; Tires; Vehicle safety
• Uncontrolled Terms: Diffusion limited oxidation
• Subject Areas: Highways; Safety and Human Factors; Vehicles and Equipment; I91: Vehicle Design and Safety;

Filing Info

• Accession Number: 01357976
• Record Type: Publication
• Report/Paper Numbers: HS-811 266
• Contract Numbers: DTNH22-03-D-08660, DTNH22-07-D-00060
• Files: HSL, TRIS, USDOT
• Created Date: Dec 1 2011 9:56AM