3. Results and discussion
Mechanical behavior of TPS films was characterized by two independent
and complementary techniques (tensile tests and quasistatic
assays). It is well known that fillers incorporation to TPS
matrixes allows improving mechanical properties of composite
materials. Fig. 1 shows stress-strain curves corresponding to TPS
and its bionanocomposites containing talc particles determined by
both techniques. As it is observed in the curves obtained by tensile
and quasi-static assays, filler addition did not modify stress-strain
behavior of TPS, showing a characteristic curve of ductile materials.
Table 1 presents mechanical properties of developed materials.
Despite different values were obtained by both techniques,
talc addition influence on TPS mechanical performance was similar.
Tensile and quasi-static experiments revealed that the lowest used
talc concentration did not affect (p > 0.05) film stiffness. Considering
results from quasi-static assays, a stiffness increment of
around 15% was observed for samples with 3% w/w talc concentration.
A 5% w/w of talc addition increased Young’s modulus
around 68 and 81%, determined by tensile and quasi-static experiments,
respectively. Incorporation of 1% w/w talc particles to TPS
formulations increased 1.2 times the maximum tensile stress,
determined by tensile tests. Both techniques demonstrated that 3
and 5% w/w talc incorporation increased significantly (p < 0.05)
TPS yield stress. Well dispersion and distribution of nanoparticles
within the matrix, attributed to good starch-talc compatibility,
allow TPS materials reinforcement (Lim, Lee, & Tay, 2009). Particlematrix
interfacial adhesion could be associated to the edge surfaces
which have hydrophilic groups such as -SieOH and -MgeOH
(Chabrol et al., 2010). In addition, Ferrage et al. (2002) reported the
presence of electronegative sites on talc tetrahedral sheets propitious
to form hydrogen bonds with polypropylene methyl groups.
Similar interaction could be expected for composites based on TPS
and talc nanoparticles.