DSC studies on pure ESBO showed the presence of crystalline
polymorphism, characteristic of some lipids, such as soybean oil
[32]. This phenomenon was seen in the DSC curve of the pure
plasticizer used in this work (Fig. 4) as a crystallization phase
prior to melting, with two endothermic peaks around 15 C and
6 C. It should also be pointed out that some clear changes in
the base line could be observed at low temperatures, but it is not
easy to attribute these bands to any phase transition since the
base line was quite unstable in this region and no Tg values could
be determined. Nevertheless, Tg values for plastisols before
curing were clearly detected by DSC (Fig. 5), obtaining an inverse
and mostly linear correspondence between ESBO concentration
in plastisols and Tg. The excess of plasticizer in the plastisol with
50 wt% of ESBO could be confirmed in Fig. 5 since the two
characteristic endothermic peaks were clearly distinguished. As
indicated, this excess in the plasticizer concentration affected the
high initial degradation temperature obtained by TGA for this
sample. In the DSC study of gaskets, only the jam lid gasket, with
the highest percentage of ESBO (Fig. 3), yielded a detectable
value of Tg at 10.3 C, because Tg from cured plastisols as well as
values for samples with low amounts of plasticizer were poorly
detected.