Influência do negro de fumo na absorção da radiação na região do infravermelho para o reaquecimento do copolímero de poli(tereftalato de etileno) - PET.
Resumen
The objective of this work was to study the influence of the use of carbon
black as infrared absorber to improve the PET resin heat-up during the
stretching blow molding of bottles. It was investigated the correlation between
the main physical properties of the carbon blacks and the source setup
conditions and the PET infrared absorption. Therefore, five carbon blacks with
different physical characteristics were selected and mixed with a PET resin
bottle grade by injection molding. The correlation between particle size, surface
area and structure of carbon black and the optical properties, rheological
behavior and heat-up of the compositions were studied. The rheological
measurements showed that the carbon blacks did not modify the profile of the
PET rheological curve; however both the viscosity and elasticity properties of
the PET were dependent on the carbon black particle size and structure. The
differential scanning calorimetry (DSC) results showed that the carbon black
particles modified the PET crystallization kinetics by increasing the induced
crystallization temperature during the cooling step. Through the L* a* b* color
measurements, it was verified that the L* color was indirectly proportional to the
carbon black content. Finally, the heat-up performance was investigated using
two methods: (a) the surface temperature measurement of samples heated
under infrared lamps and, (b) the total absorption of each composition
calculated using the spectrum data obtained by near infrared spectroscopy
(NIRS). Using the scanning electron microscopy (SEM) it was verified that the
carbon black content did not modify significantly the morphological aspect and
the fracture surface of the compositions.