RESUMO
A polyethylene (PE) film surface modification method is proposed via benzoic acid (BA) alkylation grafting to improve the surface affinity to polar substances. The procedure involves sequentially spraying AlCl3 and BA onto the heat-softened PE surface. The occurrence of the alkylation reaction was evaluated through comparative chemical, morphological, and thermal analyses. It was demonstrated that the grafting reaction of BA onto the PE film surface took place, limited to the surface layer, while preserving the bulk properties of PE. The reaction resulted in the formation of aluminum benzoate complexes, which improved the surface affinity to polar compounds. The impact of grafting on the surface properties of PE was further assessed by comparing the behavior of PE films treated with BA and untreated PE films when painted with watercolors. The PE film grafted with BA exhibited increased affinity towards watercolors, providing strong evidence of a change in surface polarity from hydrophobic to hydrophilic. These findings indicate that the proposed methodology effectively renders the PE surface paintable, even with non-toxic water-based inks, making it suitable for applications such as packaging.
RESUMO
Scanning electron microscopy (SEM) images of polymer blends followed by digital image analysis is a rapid and easy method for the measurement of particle size and dispersion. The particle size determination is done with appropriate off-line image analysis software. However, it is necessary to understand how machine parameters involved in the formation of the SEM image influence area measurements of morphological features. In this work, the influence of the accelerating voltage used during image acquisition was examined with standard samples and with polymer blend samples. A systematic study centered on two mutually exclusive assumptions of area variation or no area variation with accelerating voltage was carried out. The off-line image analysis software was then calibrated according to the assumptions. The main conclusion of this study was that kV has an important influence on area measurement in SEM images. This effect was observed for different standard materials (metallic and polymeric) and for the range of magnifications used. The higher the accelerating voltages, the greater the error at high magnification for polymer samples. As the beam energy increases, the primary electrons penetrate more deeply into the solid specimen, producing low-resolution signals. These signals degrade the image and surface details, which became less well defined. Therefore, images of polymer samples must be taken at lower accelerating voltages so the desired surface details can be imaged clearly. To avoid area measurement errors, particle measurement must be done with the calibration of the off-line image analysis software corresponding to the accelerating voltage and magnification used for the acquired images.