Maria Emília Amaral

Cold-plasma assisted grafting of cellulose fibres by acrylic monomers

Additive-free hand sheet paper samples were activated by cold-plasma in the presence of acrylic acid (AAc), acrylamide (AAm), methyl acrylate (MAc) and methyl methacrylate (MMa). The characterisation of the modified substrates showed that there grafting has occurred efficiently, as established by weight gain and FTIR spectroscopy. The contact angle measurement were carried out, as a function of pH and showed that the deposition of a drop of water at the surface of the tested samples formed 55° for unmodified substrate to 87°, for MMa-treated papers, respectively, indicating that the surface has became totally hydrophobic. ATR-FTIR spectroscopy was used to check the grafting efficiency.

Study of repeatability of an optical laser system for characterization of the paper fiber distribution and mass density

This work addresses the study of repeatability of an optical laser system, previously implemented by our research team, for characterization of the fiber distribution and mass density of two paper samples with different characteristics. In the experiment that has been carried out in the current work, both paper samples were laser scanned by the system on a total of 16 times (4 times per day in 4 different days). The data acquired and registered during the experimental work, associated to both tested samples, were then processed and the obtained results showed that the optical system is precise.

Retro-diffusion and transmission of laser radiation to characterize the paper fiber distribution and mass density

This work concerns the characterization of the fiber distribution and mass density of paper samples (extracted from paper sheets) using an optical laser system previously designed and implemented by our research team. To accomplish this task, the developed optical system was used to illuminate the paper samples with laser radiation, by opposite sides, while two image detectors captured images of the retro-diffused and transmitted laser radiation on each side of the paper samples. The captured images were then submitted to several processing routines to enable the assessment of the fiber distribution and mass density. In our experiments, two paper samples extracted from paper sheets of different characteristics were used. In terms of experimental work, the samples were both scanned with the system considering several points dispersed across their entire area, allowing the assessment of both parameters locally (for specific locations of the samples) and globally (considering the samples as a whole).