NUNES, M. A. B. S.; NUNES, MÁRIO A.B.S.; http://lattes.cnpq.br/5627276465290072; NUNES, Mário André Brito Seixas.
Resumo:
This work aims to investigate the influence of the use of different processing
temperatures on rheological, mechanical and biodegradation properties of PBAT/TPS
blends and of a biocomposite based on one of these blends. Three PBAT/TPS blends
(90:10, 80:20, 70:30) and a biocomposite based on babassu mesocarp/PBAT/TPS,
(17:58:25), were prepared by melt blending on a torque rheometer at three different
processing temperatures (150, 170, 190 °C). The samples for the tensile and
biodegradation tests were obtained by hot pressing, the latter being later buried in
simulated soil. The rheological characterization showed that higher processing
temperatures reduced significantly the molecular weight of the blends and
biocomposites, and that this reduction tended to increase with the amount of TPS in
the blend. The mechanical properties of the PBAT hardly changed with processing
temperature. In general, the mechanical properties of the blends tend to decrease with
starch content and temperature. Optimium properties were achieved for the samples
processed at 170 °C containing 20% starch and unoptimized properties for the blends
and biocomposite systems processed at 190 °C, indicating that the temperature had a
more significant effect on these properties than the amount of TPS. The addition of
fibers led to a system with higher modulus and a lower strength and elongation at break
than that of the corresponding blend at all processing temperatures investigated.
Biodegradation tests revealed high degradation rates for the blends and
biocomposites, this reduction being proportional to the amount of TPS in the systems.
The blend with the highest fraction of thermoplastic starch presented a biodegradation
rate equivalent to that of the biocomposite. PBAT did not show significant mass loss
after being buried in soil for up to 12 weeks. Morphological analysis showed that after
6 weeks burial all blends and biocomposites displayed evidence of surface erosion.
Differential scanning calorimetry analyzes showed that the increase in biodegradation
exposure time led to a progressive increase in melting and crystallization temperatures
and to a reduction in the crystallization rate of the blends and biocomposite systems.