*Applied Polymer Symposium No. 27, 193-204 (1975)*

**A STATISTICAL METHOD FOR DETERMINING THE GLASS**

**TRANSITION TEMPERATURE FROM DILAOMETRIC DATA **

**NELSON P. C. CHAO and JOHN A. CUCULO**

*Department of Textile Chemistry*

**A. RONALD GALLANT**

*Department of Statistics*

**T. WALLER GEORGE**

*Department of Textile Technology*

North Carolina State University,

Raleigh, North Carolina 27607

**SYNOPSIS**

An objective procedure for estimating the glass transition
temperature (T_{g}) from dilatomctric data is described. The
method uses the technique of fitting a segmented linear regression
model by least squares. The regression model employed may be specified
so as to allow a transition either of the first order in the
thermodynamic sense or may be constrained to fit a second order.
Methods are given for finding statistical confidence intervals for the
estimated glass transition temperature (T_{g}). Experimental
data obtained from PET fiber are used for illustration, these data
indicate a preference for the second-order transition model.