Application of smoothing methods for estimation of service life for polymers from tensile testing

We propose a procedure for extracting reliable information regarding service life of a polymer product from an experimental scatter plot obtained by mechanical tests. Consideration was given to the change in elongation at break as a result of natural weathering for stabilized polymers. We suggest using locally weighted regression scatter plot smoothing to estimate the service life (threshold time)-weathering time at which the elongation at break of a polymer reduces by half. For the first time the construction of realistic confidence intervals (accuracy of the estimations) for the service life obtained from tensile testing of aged polymers is discussed. The proposed approach is general and applicable to other degradation processes.