PBT in FR3: Measured Strength and an Illustrative Aging Forecast

The problem addressed here is a molded support immersed in natural ester fluid, which must retain its tensile strength and deformability under heat and fluid exposure. Cargill TR-610 reports measured tensile strength for PBT with 30% glass fiber at 17,673 psi initially and 10,660 psi after 2,000 hours at 170°C in FR3, and a two-point first-order proxy model was fit to exactly reproduce both of these measured values. Using that proxy, illustrative values were generated at other time points: 13,726 psi at 1,000 hours, an interpolation between the two measured points, and 9,394 psi and 4,994 psi at 2,500 and 5,000 hours, both unmeasured extrapolations beyond the measured range. The ±20% rate limits shown are illustrative scenarios rather than statistically derived prediction intervals.

Importantly, there is no held-out validation for this model, meaning these projected values are analytic examples only and do not represent ElastoSure software output or verified predictions. For product context, Cargill FR3 is the actual fluid referenced in the report, while BASF Ultradur is used only to illustrate a general category of PBT products, since the original report does not specify an exact Ultradur grade. The source for this data is Cargill's 2015 technical report, Table 11, which is non-peer-reviewed.