Worldwide Tire Survey: Inflation Pressure Retention Loss Rates

The inflation pressure of the tire impacts its performance: rolling resistance, treadwear, handling, and durability.  Reducing tire inflation pressure loss rates (IPLR), as measured by percent air loss per month, is a key parameter to improving tire performance.  Copolymers based on polyisobutylene are notable for their low permeability to small-molecule diffusants as a result of their efficient intermolecular packing.  Halobutyl rubber, both bromobutyl and chlorobutyl, is the polymer of choice in the innerliner compound due to its excellent air and moisture impermeability, and excellent flex-fatigue and age resistance. 

During the last 25 years, we have made a series of tire surveys in order to evaluate the influence of halobutyl rubber content in the tire on IPLR.  The historical trend for five major tire manufactures was to increase the use of halobutyl rubber in the innerliner compound, while reducing the liner gauge. In the last ten years, we have made surveys of tires that were manufactured and purchased around the world.  We have measured Tire IPLR and made detailed studies of the innerliner compound by analyzing the polymer composition, by determining the filler type(s) used, by quantifying the total filler use, by characterizing the volatile content, and estimating the total formula weight. It is found that statistically significant results are obtained for low Tire IPLR values to halobutyl use, region where the tire was manufactured, if the tire was manufactured for original equipment use, and if the manufacturer was from a Top 10 producer.