In this work was studied the permeation of CO2in films of high-density polyethylene (HDPE) and organoclay modified with polyvinylalcohol (MMTHDTMA/PVA) obtained from melt blending. Permeation study showed that the incorporation of the modified organoclay generates a significant effect on the barrier properties of HDPE. When a load of 2 wt% ofMMTHDTMA/PVAwas incorporated in the polymer matrix, the flow of CO2decreased 43.7% compared to pure polyethylene. The results of TEM showed that clay layers were dispersed in the polymeric matrix, obtaining an exfoliated-structure nanocomposite. The thermal stability of nanocomposite was significantly enhanced with respect to the pristine HDPE. DSC results showed that the crystallinity was maintained as the pure polymeric matrix. Consequently, the decrease of permeability was attributable only to the effect of tortuosity generated by the dispersion ofMMTHDTMA/PVA. Notably the mechanical properties remain equal to those of pure polyethylene, but with an increase in barrier properties to CO2. This procedure allows obtaining nanocomposites of HDPE with a good barrier property to CO2which would make it competitive in the use of packaging.
We studied the crystallization of
ZSM-5 zeolite by hydrothermal
treatment in the absence of organic structure directing agents (OSDA)
at 170, 180, and 190 °C, using Perlite as a natural source of
SiO2 and Al2O3. Experimental data
were fitted by nonlinear regression following the Kolmogorov–Johnson–Mehl–Avrami’s
nucleation/crystallization model in order to calculate kinetic constants
(k), induction periods (t
0), and Avrami’s exponents (n). A constant
value of n = 3.4 implicates the same mechanism in
the studied range of temperature with a contribution from three dimensions
to crystal growth and a nucleation that may include both sporadic
and instantaneous mechanisms. Different stages of crystallization
were clearly differentiated, and specific kinetics parameters were
calculated. Compared with previously reported preparations, we found
that the synthesis from Expanded Perlite is a promising alternative
as it not only avoids the use of OSDA but also consumes less energy.
Finally, a five steps crystallization mechanism has been proposed.
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