On the Structure of Porous Poly(vinylidene fluoride) Membrane Prepared by Phase Inversion from Water-NMP-PVDF System
A PVDF membrane was prepared by isothermal immersion precipitation of a PVDF/NMP solution from pure water bath. FESEM imaging of the formed membrane revealed its porous structure, featuring tight skin, macrovoids, and cellular pores. These structural characteristics were common to membranes that were formed by precipitation of amorphous polymers from harsh nonsolvents. Evidence of crystallization in the present PVDF membrane could be observed on the surfaces of the various pores in the form of branching dendrites.
Modification of PVDF membrane by two-dimensional inorganic additive for improving gas permeation
ABSTRACT In the present work, polyvinylidene fluoride (PVDF) membrane has been modified by incorporating un-exfoliated and exfoliated fillers of hexagonal boron nitride (h-BN) to enhance the gas permeation through it. In order to check the distribution and homogeneity of h-BN, PVDF/h-BN composite membranes were characterized by scanning electron microscopy, atomic force microscopy, Fourier transform infrared spectroscopy and thermogravimetric analysis. Highest permeabilities of 1.88969 × 105, 2.07866 × 105 and 1.21780 × 105 Barrer at 80 psi were obtained for PVDF/h-BN (exfoliated) membrane against pure O2, CO2 and CH4 gas, respectively. Modified Higuchi model was fitted fairly with the experimental results.
Efficacy of Biodentine as an Apical Plug in Nonvital Permanent Teeth with Open Apices: An In Vitro Study
The aim of this study was to evaluate the apical microleakage of Biodentine and MTA orthograde apical plugs and to compare the effect of thickness of these biomaterials on their sealing ability. A total of eighty maxillary anterior teeth were used. The apices were removed by cutting with a diamond disc (Jota, Germany) 2 mm from the apical root end in an attempt to standardize the working length of all specimens to 15 ± 1 mm. Both materials were placed in 1–4 mm thickness as apical plugs root canal. Root canal leakage was evaluated by the fluid filtration technique. One-way ANOVA was used in order to determine normality of dispersal distribution of parameters; thereafter, results were analyzed by Kolmogorov-Smirnov test. Overall, between microleakage values of MTA and Biodentine regardless of apical plug thickness, no difference was observed. In terms of plug thickness, a statistically significant difference was observed between the subgroups of MTA and Biodentine (p < 0.05). The apical sealing ability of Biodentine was comparable to MTA at any apical plug thickness.