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Identification of archaeological and historical textile fibres is important because it gives insight into resource management in former times. The arrival of new tools such as table-top scanning electron microscopes, have led to an increased interest in the topic. Unfortunately, there have been cases where a lack of documentation regarding instrument settings and selection criteria has led to questionable conclusions being drawn. Optical and scanning electron microscopy are powerful techniques, but they must be used correctly and with proper knowledge of their limitations. Furthermore, ancient fibre material is often difficult to examine due to issues such as sample degradation, mineralization and the scarcity of material, which means that conclusions based on a statistical analysis of a large number of fibres are essentially not possible. In a cultural heritage context, it is therefore essential to distinguish between characteristic features, by which we mean features that are often, but not always present in a particular species and distinguishing features, which are always present in a particular species and can therefore be used for identification even if only a small amount of sample material can be examined. We argue that the community will have to accept that, quite often, a secure identification is not possible and that absolute statements such as: "This textile is made of flax" will often have to be replaced by relative statements such as "The material is likely to be flax". In this paper, we address these issues as follows: first, we present a fibre identification diagram which can be used, with some limitations, to distinguish between flax, hemp, nettle, jute, hops, and cotton using optical and electron microscopy. We then move on to highlight some of the typical pitfalls of using optical and electron microscopy for fibre identification. Finally, we present measurement documentation tables for optical and electron microscopy images, which we suggest should always be included in publications. Material scarcity means that the amount of material used for investigations should be kept at an absolute minimum. It is thus crucial that results are published with proper documentation so that measurements do not need to be repeated (more material is used) in future studies. It is our hope that the measurement documentation tables will be adapted by the community and used in future publications in the field. The paper finishes with a demonstration example, presenting a fibre analysis of Viking Age textile fragments from the 10th Century with documentation tables. [ABSTRACT FROM AUTHOR]

A persistent rise in the costs of construction materials has led to the need to address this problem in line with the Sustainable Development Goals. This research employed vegetal soft and rigid fibers in a screed mortar to produce a sustainable fabric–cement matrix. Four different vegetal-dried fibers (hemp, flax, miscanthus, and bamboo) with dosages of 0.4, 0.6, 0.8, 1.2, 2, and 4 kg/m3 were used. Laboratory investigations were slump test, bulk density, air occluded, shrinkage, and mechanical strength. Scanning Electron Microscope (SEM) assessments were performed and analyzed on the natural fibers and the screed formulation. The results highlight that fiber dosages significantly influence the above-mentioned properties. [ABSTRACT FROM AUTHOR]

This study assessed the impact of alkali treatment of hemp and flax fibers on mechanical properties (determined by means of the uniaxial tensile test, impact tensile strength test and hardness test), processing properties (the course of the extrusion and injection process) and usable properties (shrinkage of molded pieces, degree of water absorption) of biocomposites on the base of poly (3-hydroxybutyric-co-3-hydroxyvaleric acid) (PHBV) biopolymer. For this purpose, 1 mm of length flax and hemp fibers was surface-modified by means of aqueous solution of NaOH (sodium hydroxide) with concentrations of 2%, 5% and 10%. The composites were made using the extrusion technology. The test specimens were produced by injection molding technology. In total, eight types of biocomposites with modified and non-modified fibers were produced, and each biocomposite contained the same filler content (15 wt.%). Their properties were compared in some cases with pure PHBV polymer. In the case of biocomposites filled with hemp fibers, it was noted that an increase of the alkalizing solution concentration improved most of the tested properties of the obtained biocomposites. On the other hand, in the case of flax fibers, there was a significant decrease in most of the mechanical properties tested for the composite containing fibers etched by 10% NaOH solution. The obtained results were verified by examining fibers and the destroyed specimens with a scanning electron microscope (SEM) and an optical microscope, which confirmed, especially, the significant geometry changes of the flax fibers etched by 10% NaOH solution. This procedure also resulted in a significant change of processing properties—a composite of this fiber type required about 20 °C lower temperature during the extrusion and injection molding process in order to obtain the right product. These results lead to the important conclusion that for each filler of the plant-origin and polymer matrix, the fiber alkalization method should be selected individually in order to improve the specific properties of biocomposites. [ABSTRACT FROM AUTHOR]