. 2023 Apr 14;18(4):e0284473. doi: 10.1371/journal.pone.0284473

Table 3. Specifics of separation indices (SIs).

SIs Expression	Interpretation for improved storage stability
SPD = Softening point difference of top and bottom sub-portions	SPD = 0
$S I_{V i s c o s i t y} = \frac{V i s c o s i t y o f t o p}{V i s c o s i t y o f b o t t o m}$	SI = 1
$S I_{G * / s i n δ} = \frac{G * / s i n δ o f t o p}{G * / s i n δ o f b o t t o m}$
$S I_{J_{n r}} = \frac{M S C R J_{n r} o f b o t t o m}{M S C R J_{n r} o f t o p}$
SI_FTIR = Absorbance differential for binder from top and bottom sub-portions at 722 cm^-1 wavenumber	SI = 0
SI_RET = Mass difference of extracted rubber from top and bottom tube sub-portions	SI = 0