Technology, Restoration and Arts Enhancement Center

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Effect of the dispersion state of minerals on the properties of cellulose nanofiber-based composite films

Publication . Alves, Luís; Ramos, Ana; Ferraz, Eduardo; Sanguino, Pedro; Santaren, Julio; Rasteiro, Maria Graça; Gamelas, José AF

The dispersion state and the efficiency of the mixture of the different components in a composite film have an important impact on its mechanical and optical properties. In the present work, the impacts of different dispersion treatments on the disaggregation state of fibrous clay particles in water, and on the properties of related cellulose nanofiber (CNF)-based composite films, were evaluated. X-ray diffraction studies, performed on samples of sepiolite and palygorskite, revealed only minor changes in the diffraction pattern when the minerals were subjected to ultrasonic treatment, with or without the addition of different chemical dispersing agents. Conversely, microscopic studies revealed important differences in the dispersion state of the samples, induced by the addition of the different dispersants, showing an improvement in the disaggregation of the mineral crystals. The composite films prepared with sepiolite (and carboxymethylcellulose, as chemical dispersant) dispersed using ultrasonic treatment, and different types of CNF, showed improved optical and mechanical properties when compared with composites of the same counterparts prepared with sepiolite dispersed using a high-speed shear disperser.

2023-03Journal article

Open access

Composite Films of Nanofibrillated Cellulose with Sepiolite: Effect of Preparation Strategy

Publication . Alves, Luis; Ramos, Ana; Rasteiro, Maria G.; Vitorino, Carla; Ferraz, Eduardo; Ferreira, Paulo J. T.; Puertas, Maria L.; Gamelas, José A. F.

Cellulose nanofibrils (CNFs) are nanomaterials with promising properties to be used in food packaging and printed electronics, thus being logical substitutes to petroleum-based polymers, specifically plastics. CNFs can be combined with other materials, such as clay minerals, to form composites, which are environmentally friendly materials, with acceptable costs and without compromising the final properties of the composite material. To produce composite films, two strategies can be used: solvent casting and filtration followed by hot pressing. The first approach is the simplest way to produce films, but the obtained films may present some limitations. In the present work, CNFs produced using enzymatic or TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical) oxidation pretreatments, followed by high-pressure homogenization, or only by mechanical treatment (homogenization), were used to produce films by both the available procedures. The films obtained by filtration + hot pressing presented higher tensile strength and Young’s modulus compared with those obtained by solvent casting. In general, a decrease in the values of these mechanical properties of the films and a decrease in elongation at break, with the addition of sepiolite, were also observed. However, for the TEMPO CNF-based films, an improvement in tensile strength could be observed for 10% of the sepiolite content. Furthermore, the time necessary to produce films was largely reduced by employing the filtration procedure. Finally, the water vapour barrier properties of the films obtained by filtration are comparable to the literature values of net CNF films. Thus, this technique demonstrates to be the most suitable to produce CNF-based composite films in a fast way and with improved mechanical properties and suitable gas barrier properties.

2022-02-23Journal article

Open access

Dodging Nostalgia: filming and dealing with facts in industrial heritage sites

Publication . Sol, Hermínia; Luz, João

Documentary film is commonly seen and defined has a genre with social engagement ambitions. In fact, many directors and critics view it as a form of social history by giving central roles to individuals or communities that tend to be rendered invisible or voiceless by mainstream media. This perspective gains relevance when one considers films which deal with labour relations in manufacturing plants which, often, expose forms of psychological violence inflicted by those in power positions towards the underprivileged. Filmmakers such as Luc Decaster, Michael Moore as well as Steven Bognar and Julia Reichert, to mention but a few, have all worked on film narratives that explore the process of deindustrialization in their countries of origin. While exposing the complexity and disturbing effects of the dismantling of an industrial order, the adopted stance is one that refuses to glorify the outgoing paradigm. Inspired by the work of the aforementioned directors, the authors of this paper have ceased the opportunity to work on a film about the extinction of a paper producing industrial node in Tomar (Portugal) and on the repercussions for the region. During the course of filming, however, they felt the need to produce a theoretical reflection on the negotiating process adopted to reach a balance between the perspectives of elements of former managerial and technical staff. With that in mind, this proposal aims at sharing their musings as well as the difficulties found during the research and shooting periods to distance themselves from an industrial sublime nostalgic narrative that effaces the complexity of class conflicts, along with the violence of manually assembled work, by focusing on the grandeur of the buildings and of the machinery. Special emphasis will be placed on the difficulties of dodging a nostalgic industrial sublime narrative. Firstly, because this narrative is still very much ingrained in a prevailing industrial heritage protection discursive trend and, secondly, because it was a narrative shared by white and blue collar-workers alike. Hence, the sanitizing and violent features of the dominant nostalgic discourse will be analyzed by resorting to a work still in progress.

2021-11-05Conference object

Open access