Poly$($ethylene terephthalate$)$ was crystallized at $110C$ and the densities were measured

after the indicated time of crystallization $($A$.$ Keller, G$.$R$.$ Lester, and L$.$B$.$ Morgan, Phil.

Trans. R$.$ Soc. London, $247$A$,1,1954).$ Using density as the property measured to deter$-$

mine crystallinity, evaluate ${}_c$ as a function of time for these data. By an appropriate

graphical analysis, determine the Avrami exponent $($in doing this, ignore values of ${}_c$

$0\mathrm{.}15,$ since errors get out of hand in this region$).$ Calculate $($rather than graphically evalu$-$

ate$)$ the value of $K$ consistent with your analysis.