Search

A small framed display panel holds a selection of paper and media common in works on paper plus a set of Blue Wool Standards. The selection of materials and design of the panel including two types of glazing are presented, and the purpose of the panel as a tool for explaining the effects of light on materials is discussed. At the centre of the panel are watercolour samples prepared using primary colours in mixed washes that illustrate hue shift resulting from selective fading of one colourant.

Six face- and back-mounted chromogenic print samples (each 120 × 160 cm) and one pre-damaged original photograph (120 × 120 cm) were exposed to alternating temperature conditions. Cold storage was set at 8 °C with a slightly fluctuating relative humidity at an average of 55 % in a cooling chamber; room temperature storage occurred at 19 to 27 °C depending on the prevailing weather conditions. The samples were exposed alternatingly to these setups in a 24-hour rotation over five weeks to assess the effect of strong and rapid fluctuations on the stability of the composite. After about one week under the extreme, stress-intensive testing conditions, irreversible deformation, and a local loss of translucency occurred. Further local delamination was observed on the pre-damaged original artwork. Exceeding the dew point temperature, which occurred in our experimental setup and should be avoided, resulted in condensation on the acrylic surface and led to extensive streaks and, in combination with the electrostatic charge, to extreme dust deposits. These findings suggest that cold storage cannot be recommended for face- and back-mounted chromogenic prints.

Newly produced face-mounted photographic prints feature perfectly clear, smooth acrylic surfaces. Cleaning these integral but vulnerable surfaces poses a high risk of mechanical damage, which increases with every repetition. We tested the mechanical impact of dry-cleaning to optimize the cleaning process of face-mounted artworks at the Kunstsammlung Nordrhein-Westfalen in Düsseldorf. We used four different microfibre cloths on one acrylic common in the production of face-mounted photographs. One additional option consisted of an antistatic silicone roller used for preliminary cleaning on one half of the plates. The plates were contaminated with street particulate soiling and fingerprint stains. All glasses were cleaned in either circular or straight wiping motions. The plates were photographed in dark field to document any side effects of cleaning involving scratches, smudges, and the static charge of the acrylic after cleaning. The microfibre cloth SM 711 in combination with the silicone roller performed best in the test. However, the same cloth, pre-used and washed, significantly increased scratch formation. These findings provide effective and safe recommendations for risk-minimized future cleaning procedures for face-mounted photographs.

The three treatment phases for pressure-sensitive tape removal included in this review are: removal of the carrier, adhesive removal from the paper surface, and adhesive removal from the paper interior. The latter process requires organic solvents. Solvent selection via the Teas chart or Zumbühl’s system are compared. Teas triangular chart supports the calculation of solvent mixtures with ideal mixing properties; Zumbühl’s bi-axial parametrization system supports solvent selection when solvent mixtures exhibit non-ideal behaviour and highlights vapour pressure as the solvent selection criterion. Strategies for working with solvents include a discussion of solvent mixtures and their application and the introduction of a suction disk design. Effects and common side effects of treatment are presented with examples. This review supports novices and practitioners in their treatment choices when dealing with the removal of pressure-sensitive tapes., Die drei hier vorgestellten Behandlungsphasen für die Entfernung von Haftklebeband umfassen die Abnahme des Trägers sowie die Ablösung des Klebstoffs von der Papieroberfläche und aus dem Inneren des Papiers. Für letztere sind organische Lösungsmittel erforderlich. Die Auswahl der Lösungsmittel wird anhand der Teas-Tabelle oder des Zumbühl-Systems verglichen. Das Teas-Dreiecksdiagramm unterstützt die Berechnung von Lösemittelgemischen mit idealen Mischeigenschaften, das biaxiale Parametrisierungssystem von Zumbühl unterstützt die Lösemittelauswahl bei Lösemittelgemischen mit nicht idealem Verhalten und hebt den Dampfdruck als Lösemittelauswahlkriterium hervor. Strategien für den Umgang mit Lösemitteln beinhalten eine Diskussion von Lösemittelgemischen und deren Anwendung sowie die Einführung eines Saugscheibendesigns. Wirkungen und häufige Nebenwirkungen der Behandlung werden anhand von Beispielen dargestellt. Diese Übersicht unterstützt Lernende und Praktizierende bei der Wahl der Behandlungsmethode für die Entfernung von Selbstklebebändern.

Ink corrosion on parchment is a phenomenon that, unlike its counterpart on paper, has so far been little researched. The same applies to the options for conservation treatment. In order to provide a guide for conservation practice as well as further research, five water-based treatment methods were examined: calcium phytate with pH 5.3 or 3.0, a 0.5% (w/w) solution type B gelatine, a 1% (w/w) solution of phytic acid at pH 2.2 and calcium phytate in combination with gelatine. These were tested on 70 specimens cut from on piece of buffed vellum and 36 specimens from an early modern deed on parchment that showed signs of ink degradation. After treatment and accelerated ageing, the samples were examined with colorimetry and ATR-FTIR spectroscopy and tested with bathophenanthroline for free iron ions. None of the tested treatment methods achieved a fully reliable inhibition of ink corrosion, but apart from a moisture-catalysed acceleration of degradation reactions, no adverse effects were observed either. Results from ATR-FTIR suggest that oxidation plays a more important role in damage related to ink corrosion of parchment than hydrolysis.

Correctness and reliability of molar mass data by viscometry in organometallic solvents (cuen, cuoxam, cadoxen) are compromised by the alkalinity of these solvents which causes immediate depolymerization especially in the case of pulps with higher carbonyl content (oxidative damage). The viscosity values thus correspond to the molar mass after the beta-elimination reactions that underly these degradative processes, which is sometimes significantly smaller than the molar mass determined by gel permeation chromatography (GPC) in the non-degrading solvent system DMAc/LiCl. Despite this well-known drawback, viscosity measurements have become a standard approach for molar mass measurements due to their ease and fastness, especially in the pulp and paper industries. A potential way to reduce the inherent error of these molar mass determinations via viscosity measurements is a reductive treatment prior to dissolution of the pulp in the organometallic solvents, which converts the labile, alkali-sensitive carbonyl structures back to the respective alcohols. Using sodium borohydride (NaBH4) on different types of cellulosic pulps, we demonstrate the beneficial effects of such a reduction step on the determined degree of polymerization (DP) for all three common solvents: cuen, cuoxam and cadoxen. Molar mass distributions and profiles of carbonyl groups were determined by GPC and by carbonyl selective fluorescence labeling (“CCOA method”). Such a reductive treatment was especially valuable for hemicellulose-containing pulps. While the decreased measurement error according to the new protocol is beyond doubt, an immediate acceptance in the pulp and paper industries is at least questionable, because the new, more correct data would not agree with the old – wrong, but consistent – numbers accumulated over years and decades. In the long run, however, the new, improved protocol will prevail here as well due to its lower error rate.

D5 (decamethylcyclopentasiloxane), a non-polar solvent that evaporates slowly, was tested for its suitability as a temporary masking agent for water-sensitive media on paper objects undergoing aqueous treatment. Three different treatment-related settings were tested on five different paper types, some prepared with water-soluble inks. In 10-min water immersion treatments, D5 proved largely ineffectual in protecting the water-soluble inks. In conjunction with melt-applications of cyclododecane, the addition of D5 enhanced its barrier function only in one case. To test the ability of D5 to prevent tideline formation, the test samples received applications of water, acetone, and a water-ethanol-mixture, creating an interface with freshly D5-impregnated areas. The papers were evaluated visually (VIS, UVA), some after artificial aging. D5 diminished the formation of visible tidelines in the two internally sized papers with low water absorbency in contact with acetone and the ethanol-water mixture, but did not prevent tidelines in contact with water. It also did not protect water-absorbent paper. The results indicate that D5, which is miscible with ethanol and acetone, may disperse tidelines caused by these solvents, but it proved largely insufficient for protecting media during water immersion.

Among bleaching agents available in paper conservation, hydrogen peroxide (HP) is a versatile choice that has many advantages in the removal of discoloration from paper. However, its well-known rad...

Hydrogen peroxide (HP) residues that remain after the conversion of blackened lead white may cause unwanted paper discolouration and degradation. Four VOCs sorption materials were tested for their ability to eliminate HP gas evolving from the treated substrate. This was tested by measuring the change in HP concentration in aqueous solution and in an enclosed air space in the presence of MicroChamber® Interleaving Paper, Corrosion Intercept® film, Zorflex® activated carbon cloth (ACC) and iron sulphate-impregnated paper. Detection with the colour indicator Quantofix® test strips and a Dräger X-am® 5100 single gas detection device showed that ACC is by far most efficient in decreasing the HP concentration. ACC was also effective in preventing paper discolouration in test objects that had been HP-treated for lead white conversion and then were stored sandwiched between ACC. Although ACC may not eliminate all HP from the substrate, it can diminish its negative effects on the treated object and protect other objects in the vicinity.

The viability of fiber optics reflectance spectroscopy (FORS) for the differentiation of red chalk drawing media was investigated, focusing on the group of drawings from the workshop of Giovanni Battista Piranesi (1720–1778) at the Staatliche Kunsthalle Karlsruhe, Germany. The evaluation of spectra was supported by principal component analysis (PCA). The method was tested on mock-up drawings made with recently acquired natural and synthetic red chalks of known origin. It was possible to sort these mock-up drawings according to chalk type and application technique. The compositional differences of these reference chalks were confirmed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Subsequent FORS analysis of selected original drawings revealed the existence of several closely grouped clusters, implying similarities on the basis of the underlying spectral features among the historical red chalks used in Rome. These similarities distinguished the historical drawings from the red chalk mock-up drawings, except for the drawings made with red chalk samples from the area near the town of Theley, Germany, which were shown to bear close similarities to those in the cluster of historical samples.

An etching that was visibly damaged as a result of previous bleaching with a 5.6 % aqueous sodium borohydride solution underwent retreatment involving washing to stabilize the embrittled paper and to remove potentially present bleaching residues. During a final immersion in a dilute calcium hydrogen carbonate solution administered for deacidification, an unexpected and severe blistering occurred that is explained as a recurrence of previous bleaching-related blistering. The blisters were laid down. The treatment concluded with a consolidation of the bleach-damaged paper surface using a 0.5 % gelatine solution applied by misting.

High performance daylight LED lamps are compared with HID lamps for light bleaching of paper. The LED can be placed in closer proximity to the object than the HID lamps, causing a significantly increased, uniform light exposure. Two commercial LED systems with 4000 K and 6500 K colour temperature were installed in a convertible test device with a polypropylene tray in default exposure distance of 10 cm and 20 cm. A HID lamp in 60 cm and 120 cm distance served as a reference. Samples of two naturally aged rag papers were bleached with both LED systems and with the HID while immersed in water. All three light sources increased brightness (CIELAB L*), though the LEDs with 4000 K colour temperature were most effective. They had no negative effect on the molar mass and the cellulose carbonyl group content while LEDs with 6500 K colour temperature caused molar mass decrease and carbonyl group increase. LEDs of a 4000 K or similar colour temperature are a promising option for improved light bleaching of paper, reducing the treatment and aqueous exposure time and eliminating UV radiation.

Although cellulose is the oldest macromolecule we have known, its intrinsic properties are still not well understood because of the lack of suitable solvents. The recent development of ionic liquids enables preparation of cellulose solutions in which cellulose molecules are supposed to be dispersed molecularly. Conventionally a semi-flexible-chain model or a worm-like chain model has been applied to describe the dilute solution properties of cellulose. A semi-flexible chain model is specified in terms of a persistent length to determine the chain stiffness of a solute molecule, completely neglecting details of the solvent–solute interaction, and the discussion is mainly focusing on the conformation of a solute molecule. In this paper we adapt a cylinder model which at least specifies the local shape of a solute molecule. Since the ionic liquids are now available as a new solvent of cellulose, we have prepared cellulose/ionic liquid solutions for small-angle X-ray scattering (SAXS) measurements which provide information on the local structure of cellulose molecules in the restricted range. The SAXS measurements were performed on the cellulose/ionic liquid solutions at two independent synchrotron facilities and confirmed the consistency of the observed scattering profile. Standard methods were applied to analyze the scattered data first, and afforded a model for representing a cellulose molecule in ionic liquid solutions. Two types of ionic liquids were used, and it was ascertained that cellulose was not degraded under the conditions used. The solution characteristic was found to change by heating during the preparation of each solution. The heating effect on the conformational change of cellulose was discussed in terms of the solute–solvent interaction from the simulation with a coaxial double layer cylinder model. The state of solvent packing was considered as well from the thickness and relative electron density of the sheath in the simulated coaxial double layer cylinder model.

Literature is strongly contradictory about the molecular reasons for yellowing and brightness reversion of pure (lignin- and hemicellulose-free) celluloses, such as in highly bleached pulps, bacterial cellulose, or cotton linters. While oxidized groups—carbonyls (CO) and carboxyls (COOH)—have been recognized as the initiators of yellowing, they are generally always found together; thus, their effects are permanently superimposed in real-world cellulose. For this reason, their individual contributions could not be reliably determined. To tackle this conundrum, we have used a two-stage study: the employment of glucopyranose-derived model compounds and the use of special cellulosic pulps. Both substrates had either only carbonyl functions, only carboxyl functions, or defined ratios of both functionalities present at the same time. The model compounds alone already provided strong indications of the CO-related and COOH-related effects, and further confirmation was obtained by the pulp study. Here, in regard to the polymer case, the carbonyl groups are the minimum functional unit in cellulose responsible for chromophore generation (termed as the “CO effect”). The carbonyl groups are the precursors for the chromophores that are formed later upon yellowing/aging. Chromophore formation increases strictly linearly with the carbonyl content at a constant given carboxyl content. Carboxyl groups alone (i.e., in the absence of carbonyl groups) are fully innocent regarding the color generation. However, they have a strong promotive action when carbonyl groups are present (termed as the “COOH effect”), which includes acidic catalysis and an additional activation by electronic effects. The general roles of CO and COOH are the same for all aging types (e.g., thermal, acidic, or alkaline), while the respective rates of chromophore generation evidently depend on various parameters such as the temperature, medium, and pH value.

Lightweight cellulose II aerogels featuring densities of about 40–70 mg cm−3 were prepared from 1 to 3% solutions of different pulps in hot (60°C) tetra-n-butylammonium fluoride (TBAF)·H2O/dimethyl sulfoxide (DMSO) by (i) the coagulation of cellulose with EtOH to afford self-standing, transparent and homogeneous gels, (ii) gel ripening and washing, (iii) solvent exchange and (iv) supercritical carbon dioxide (scCO2) drying. Size exclusion chromatography (SEC) analyses confirmed that the chemical integrity of cellulose is largely preserved at short dissolution times. Dissolution of more than 2% of cellulose at a sufficiently low viscosity for solution, casting was achieved after the water content of TBAF was reduced to a value equaling that of the monohydrate. Intriguingly, the obtained aerogels featured higher specific surfaces (≤470 m2 g−1) than comparable materials prepared from other cellulose solvents. This is due to the particular morphology of TBAF aerogels, which is supposedly formed by spinodal decomposition of the cellulose/solvent mixture upon exposure to the cellulose antisolvent. As a result, largely homogeneous three-dimensional (3D) networks of agglomerated cellulose spheres were formed, which simultaneously acted as supporting scaffolds for interconnected micron-size voids. As cellulose spheres are composed of very small interwoven nanofibers, TBAF-derived aerogels contain a high portion of micropores and small amounts of mesopores, too.

Lignosulfonates (LSs) are the main components of the byproduct of sulfite pulping processes accumulated in large quantities of hundreds of kilotons per year. Furthermore, they are currently the most widely utilized form of lignin due to their chemical and physical properties. LS molar mass characteristics determine their functional properties; however, there is a lack of fast and precise methods for LS molar mass analysis. The complex LS structure after pulping as well as the presence of considerable amounts of impurities in the raw sulfite spent liquor require tedious and time-consuming sample purification steps if conventional size exclusion chromatography (SEC) is to be used for analysis. Asymmetric flow field-flow fractionation (AsFlFFF) represents a good alternative to the conventional SEC technique, as the absence of a stationary phase allows purification and molar mass analysis of nonpurified industrial black liquors in one step, resulting in a drastically simplified procedure. The method’s applica...

The dihydroxyacetophenones 2,5-dihydroxyacetophenone (2,5-DHAP) and 2,6-dihydroxy-acetophenone (2,6-DHAP) belong to the key chromophores in cellulosic materials. The pulp and paper industry targets these key chromophores in their bleaching sequences to obtain brighter products. 2,5-DHAP and 2,6-DHAP were degraded with hydrogen peroxide in alkaline media, similar to conditions of peroxide bleaching (P stage) in industrial pulp bleaching. Degradation product analyses were performed by GC–MS and NMR. The degradation reaction starts by loss of acetic acid originating from the acetyl moiety of the dihydroxyacetophenones (Baeyer–Villiger rearrangement). Further reaction steps involve introduction of another hydroxyl group at C-1 (previously acetyl bearing), and further oxidation of the resulting trihydroxybenzene to quinone intermediates which are ultimately degraded to a mixture of low-molecular weight carboxylic acids.

According to published studies, certain nonaqueous solution-based treatments can be highly effective for prolonging the useful lives of bound volumes, within which the paper had been formed under acidic papermaking conditions. Such treatments, which typically use reactive alkoxide-based organometallic compounds dissolved in low-surface-tension liquids, have been shown to decrease the tendency of the paper to become brittle during long storage or during accelerated aging. This article reviews published evidence concerning the underlying mechanisms of such treatments. Evidence suggests that dissolved alkoxides and related carbonated alkoxide-based compounds are able to react directly with acidic species within acidic paper during treatment of books. Such reactions help explain the demonstrated effectiveness of nonaqueous solution-based deacidification treatments.

Chemical modification by attaching functional groups to lignocellulosic pulp fibers might be a strategy for improving the pulp, and thereby, paper properties. Several studies have described positive effects on paper strength properties for handsheets prepared from cationic-modified pulp or pulp fractions. This study addressed whether these effects are related to the cationic groups, e.g., by increasing electrostatic attraction and thus paper strength, or rather side effects of the chemical modification process, e.g., fiber flexibilization. To eliminate or at least minimize these side effects, only the fines fraction, which was already highly flexible, was cationized. While the addition of cationized fines affected various pulp and paper properties, most notably drainage time, no difference in strength properties was observed when comparing the addition of cationic or unmodified fines to different pulps or fractions thereof.

Background: The water unextractable arabinoxylans (WUAX) contain beneficial phenolic compounds that can be used for food rather than for animal feed. The antioxidant activities of defatted rice bran obtained by xylanase-aided extraction is reported herein. The chemical and molecular characteristics of extracted fractions were investigated.; Results: The WUAX hydrolysate precipitated by 0-60% ethanol (F60), 60-90% ethanol (F6090), and more than 90% ethanol (F90) had decreased molar masses with increasing ethanol concentration. The fractions of interest, F60 and F6090, contained 75% arabinoxylans with ferulic acid as the major bound phenolic acid, followed by p-coumaric acid. According to chemical-based antioxidant assays F60 and F6090 exhibited higher diphenyl-1-picrylhydrazyl (DPPH) radical scavenging and ferric iron reducing ability than F90 which contained minor contents of small sugars and free phenolic acids. In cell-based antioxidant assays, using the fluorescent 2',7'-dichlorofluorescein diacetate probe, all three fractions were potent intracellular scavengers.; Conclusion: The high molar mass of WUAX hydrolysates with high amount of bound phenolics contributes to the chemical-based antioxidant activity. All fractions of WUAX hydrolysates showed high potent intracellular scavenging activity regardless of molar mass, content and the component of bound phenolics. © 2017 Society of Chemical Industry.; © 2017 Society of Chemical Industry.

The detection of individual chromophores that contribute to the overall discoloration of paper or pulp ("yellowing") is a challenge because these substances are only present in extremely small amounts (ppm to ppb range). In this work, paper spray (PS) coupled with mass spectrometry was used to detect a low-concentrated cellulosic key-chromophore, 2,5-dihydroxyacetophenone (DHAP). Sensitivity was enhanced by derivatization with Girard's reagent T (GT). DHAP was successfully detected in historic paper samples and also was applied to model papers in order to investigate different factors that influence its generation: temperature, time, relative humidity, and the presence of iron ions, by means of a full factorial design. The main factors, temperature and relative humidity, have the most impact on the generation of DHAP, but the interactions between the factors are also significant and are therefore important for the degradation process. The historical papers containing DHAP were then compared to the artificially aged samples. The results were confirmed by independent, accurate mass measurements.

Studies of cellulose aging and yellowing that involved a 1,4-dimethyl 3-keto β-d-glucoside (compound 1) model of oxidized cellulose led to a hemi-hydrated crystal of title compound 2 (1,6-dihydroxy-3,8-bis-hydoxymethyl-5,10-dimethoxy-4,9-dioxa-tricyclo [5,3,1,1,2,6] dodecane-11,12-dione). The same compound 2 was isolated in low yield from “real-world” oxidized and aged cellulosic pulp. Formation of compound 2 implies cellulose chain cleavage and, unexpectedly, cross-linking during aging. X-ray diffraction revealed an encompassing 10-membered ring whose two carbonyl group bridges define two eight-membered rings and three six-membered rings. The central six-membered ring is antecedent to 2,5-dihydroxy-1,4-benzoquinone (compound 3), a potent and nearly ubiquitous chromophore in aged cellulose; the outer rings derive from the keto-glucosides and have 4C1 and 1C4 shapes with gt and rare tg O-6 positions. Weak trans-annular interactions between >C=O carbon and ring oxygen atoms were confirmed with Atoms-in-Molecules theory. That theory was also used to analyze a questionable cyclic hydrogen bond and bonds between adjacent O–H and carbonyl oxygens.

Bleaching in paper conservation is a complex, highly invasive treatment that involves decisions regarding cultural, aesthetic, technical and scientific parameters. We present an overview of key req...

Fibers resulting from pulping of wood are negatively charged by nature. This charge might be reversed by chemical modification for different applications. In this study, different options to determine the degree of substitution (DS) with cationic groups introduced using 2,3-epoxypropyltrimethylammonium chloride, a common cationization reagent, are compared. Classical analytical methods for this purpose include elemental analysis, which is unspecific, and titration, which is sensitive toward impurities and highly elaborate. These are complemented by fast and robust approaches based on infrared spectroscopy or thermogravimetric analysis. The absorption increase at 1480 cm−1 is specific for the introduced R-NMe3 and linearly correlated with the DS. For bleached Kraft pulps, cationization splits the thermal degradation of cellulose in two phases, their ratio being roughly proportional to the DS. Both methods require virtually no sample preparation. Infrared spectroscopy is particularly easy to apply and allows a quantification of pulp cationization in short time.

Any cellulosic pulp consists of particles of different dimensions. When trying to understand and control its properties, it is important to consider not only the bulk amount of long fibres, but also the material known as ‘fines’, which may comprise between 1 and 40% of a pulp. These fines have a great impact on the behaviour of pulp, on its processing, and on the characteristics of the resulting products. We compiled a review of research efforts to characterise the fines fraction by origin, morphology, and chemical composition, and to evaluate the fines’ effects especially in papermaking. The main feature of fines is the large specific surface area associated with their size. Their chemical constitution, particularly their charge, and the magnitude of their surface are the basis for their interactions with other pulp components such as extractives, fillers, and retention aids. The surface of fines affects drainage, as well as sheet density and strength. Several optical paper properties are influenced by the morphology of fines and by their chemical composition, which deviates from that of the long fibre fractions. The targeted utilisation of fines is a potential control variable in papermaking applications in order to obtain desirable paper properties.

The results of a research project on verdigris on paper have been applied in the conservation of a celestial atlas and a series of printed books with images of cities in Renaissance time. Paper degraded by verdigris was chemically stabilized by applying a solution of benzotriazole, a copper complexing agent, in ethanol by brush from the verso. Tears and brittle areas were mechanically stabilized with pre-coated Japanese tissue papers. The copper ion content and the effect of complexation were monitored with self-prepared copper ion indicator papers. Paper samples with different concentrations of benzotriazole were light-aged to evaluate the effect of yellowing.

Zusammenfassung Nach einer kurzen Einführung in die Technologie der Papierherstellung und der Mengenentsäuerung werden zunächst die Entwicklungen auf dem Gebiet der Qualitätskontrolle aufgezeigt. Zurzeit sind der pH-Wert, die alkalische Reserve und ihre Verteilung die Hauptkriterien zur Bewertung des Behandlungserfolgs. Da diese destruktiven Messmethoden nicht an Originalobjekten erfolgen können, muss ein universell einsetzbares Testpapier definiert werden. Im Wesentlichen muss dieses Testpapier das Absorptionsverhalten eines Entsäuerungsreagenzes und dessen Reaktionen mit im Papier vorhandenen Säuren darstellen können. Passend dazu müssen entsprechende Messmethoden den Entsäuerungserfolg zweifelsfrei darstellen können. Mit der Kombination von geeignetem Testpapier und spezieller Celluloseanalyse wurde hier im Rahmen der ISO / TS 18344 ein neuer Weg beschritten.

Fibers resulting from pulping of wood are negatively charged by nature. Both the cellulose and hemicelluloses contribute to the anionicity. The negative charge of cellulosic material can be reversed with the same reagent commonly used for the cationization of starch. In this study, a bleached Kraft pulp was cationized in systems with different water-miscible organic solvents. Replacing 90% of the water with isopropanol and particularly with tetrahydrofuran yielded higher degrees of substitution and increased reaction efficiency. The degree of substitution depends on the concentration of the cationization reagent in water; partially replacing water with tetrahydrofuran can simulate a higher concentration while maintaining supramolecular properties, such as crystallinity and polymer chain integrity.

The effect of the degradation induced by the solvents for cellulose cuoxam and cadoxen and its dependency on the nature of the carbonyls in oxidatively-damaged cellulosics was investigated by combining a novel approach of sample regeneration and gel permeation chromatography coupled with carbonyl-selective labelling for reliable molecular characterization. The type of cellulosic pulp, degree and mode of oxidation and dissolution time were considered. Results show that the main discriminating factors in determining the degradation of oxidatively-damaged celluloses in alkaline dissolving media are: (1) the type of pulp, i.e. hemicellulose-containing pulps are more severely compromised; (2) of particular relevance, the prior oxidation mechanism, meaning not only the amount of oxidized moieties (greater oxidation, greater solvent-induced damage) but also their position on the chains (i.e. peroxide-oxidized cellulose is more unstable than hypochlorite-oxidized cellulose).

Iron gall inks are known to be detrimental to the permanence of historic documents. Among the transition metals present, copper is the greatest threat and an open challenge due to the lack of Cu-specific treatments. In this study, we address the inhibition of copper by comparing extraction (a newly proposed glucose-based treatment) vs. chelation (phytate-based) approaches in terms of performances in scavenging copper and slowing the degradation rate, and of possibly induced side effects. Results show that the glucose treatment partially extracts copper, but it causes long-term damages to paper, i.e. increased fragility and discoloration. The phytate protocol was found beneficial in inhibiting the catalytic activity of copper-rich inks. It limits both long-term oxidation and hydrolytic breakdown of samples without compromising the visual appearance.

The detection of individual chromophores that contribute to the overall discoloration of paper ("yellowing") is a challenge because those substances are only present in very small amounts. In this research, two analytical approaches based on ambient ionization techniques, namely, desorption electrospray ionization and paper spray, both coupled to mass spectrometry, are compared to each other with regard to their suitability for detecting acetylated cellulosic key chromophores. The paper spray approach proved to be the more sensitive and versatile method. Subsequently, paper spray (PS)-mass spectrometry was applied to model papers and historical papers in which the acetylated chromophores were detected successfully. Independent accurate mass measurements confirmed the results obtained from reference compounds, model samples, and real-world specimens.

We present wetting, hygroscopicity, and interfacial activity of hemicellulose with respect to etherification and contrast it to their potential as interfacial modifiers, which is demonstrated by oil-in-water emulsification containing up to 60 vol% of the oil phase. Tunable amphiphilicity of hardwood and softwood hemicelluloses, xylans, and galactoglucomannans, respectively, was accomplished via controlled etherification. A series of degree of substitution (DS) of hydroxypropylated and 3-butoxy-2-hydroxypropylated ("butylated") grades was synthesized. The hemicellulose ethers were characterized by gel permeation chromatography, spectroscopic techniques, such as NMR, and contact angle measurements. An attenuated total reflectance infrared method was developed for fast identification of the DS. Near infrared analysis was utilized to explore the hygroscopicity of the material and to perform principle component analysis. The modification to butylated grades decreased the hygroscopicity, whereas the hydroxypropylated grades bound moisture. All of the hemicellulose ethers were water-soluble. The interfacial tension of the aqueous hemicellulose solutions was determined by pendant-drop tensiometer, and it was demonstrated to be dependent on the degree of modification.

Advanced approaches to wound healing have attracted much attention in the last decades due to the use of novel types of dressings that provide a moist environment and take an active part in wound protection and tissue regeneration processes. The materials for novel wound dressings should have a set of features that will contribute to efficient skin recovery. The use of bacterial cellulose (BC) is attractive for advanced wound management because of the favorable characteristics of BC, such as its biocompatibility, non-toxicity, mechanical stability, and high moisture content. Numerous approaches can be taken to modify BC to address the shortcomings of the native material and to optimize its biocompatibility, water uptake and release, and antimicrobial activity. This review highlights possible pathways for functionalization of BC, affecting all levels of its structural organization. The focus is on post-production treatment of BC, although selected studies concerning in situ modifications during the biosynthesis process are also emphasized.

Dialdehyde cellulose (DAC) has gained increasing interest because its (masked) aldehyde functionalities promise a rich follow-up chemistry and further conversion into different derivatives with varying properties. So far, the question of degradation upon DAC production and the resulting molar mass changes have remained unanswered since the problem of molar mass determination of DACs had not been solved. In this study, we present a comparison of two methods based on aqueous eluants, size exclusion chromatography and asymmetric flow field-flow fractionation (AsFlFFF), to determine the molar mass distribution of highly oxidized and thus water-soluble DACs, and to elucidate the impact of oxidation on the chain length of different cellulose substrates. Molar masses were determined by multi-angle laser light scattering in the case of both separation systems. The measurements were complemented by dynamic light scattering. AsFlFFF demonstrated an overall better separation efficiency, but at the expense of increased time consumption for method development. The results of molar mass analysis strongly depended on the eluant. Hemiacetal crosslinks are stable in near-neutral, low ionic strength eluants, while they have a tendency to be cleaved in acidic eluants or in solvents of higher ionic strength. By comparison of different dissolution strategies the optimal conditions for DAC analysis are proposed for both separation techniques. It is concluded that the extent of degradation upon dissolution can be significantly minimized by controlling the dissolution parameters, but degradation cannot be avoided completely.

Vibratory ball milling of cotton in the presence and absence of styrene was studied by electron paramagnetic resonance spectroscopy, gel permeation chromatography and ultraviolet resonance Raman (UVRR) spectroscopy. Mechanoradical formation in ball milling of cellulose was detected, but the radical content was significantly lower and the molar mass slightly higher in the presence of styrene. UVRR also showed a small but consistent increase in aromatic signal, even after 5 h acetone extraction. A small portion of styrene was attached to cellulose, which was observed as an increase in the aromatic band intensity. Stabilization or a slight increase in molar mass of the samples that were milled in the presence of styrene was also observed. Overall, under the studied conditions, ball milling is not sufficient to significantly polymerize styrene onto cellulose. For future trials of mechanochemical copolymerization, it is recommended that a vacuum or an inert atmosphere be used.

A round robin on GPC of a wide range of different pulp samples was conducted among leading groups in cellulose analysis. The aim was to survey the status quo of the methods available to date. The pulp samples covered not only fully-bleached dissolving pulps but also bleached paper pulps and one un-bleached sample. The methods applied were current state-of-the-art GPC with RI, MALLS, and viscosimetry detectors. Different dissolution protocols were compared as well. Following from the obtained results, more standardized protocols were proposed for approaches with different equipment (RI or MALLS/RI) and solvent systems (direct dissolution or derivatization). Major influencing factors, such as derivatization compared to direct solution, calibration versus light scattering and in-between lab variation, were discussed.

The chromophore release and identification method isolates well-defined chromophoric substances from different cellulosic matrices, such as highly bleached pulps, cotton linters, bacterial cellulose, viscose or lyocell fibers, and cellulose acetates. The chromophores are present only in extremely low (ppm to ppb) concentrations. The concept of primary and secondary chromophores is introduced, with primary chromophores arising only from the polysaccharides inherent to cellulosic materials. Secondary chromophores also include atoms from the chemicals used to process the cellulose. Most primary chromophores belong to one of three compound classes: hydroxy-[1,4]-benzoquinones, hydroxy-[1,4]-naphthoquinones, and hydroxyacetophenones. Among them, three individual compounds dominate: 2,5-dihydroxy-[1,4]-benzoquinone, 5,8-hydroxy-[1,4]-naphthoquinone, and 2,5-dihydroxyacetophenones, amounting to more than 80 % of the total isolated chromophores in most cases. In lignin-free cellulosics, these three compounds can thus be regarded as key chromophores. The prevalence of these molecules is due to both exceptionally strong resonance stabilization, as reflected in delocalized double bonds, and their ready reformation from carbohydrate degradation products by recondensation reactions. The findings that (a) most chromophores in lignin-free cellulosic materials belong to only three compound classes and that (b) three chromophore compounds make up the bulk of the chromophore mixtures are foundational for future bleaching research: Based on this knowledge, specific searches for optimized bleaching conditions can now concentrate on these compounds and still cover the vast majority of chromophores.

2,5-Dihydroxy-[1,4]-benzoquinone (DHBQ) is one of the key chromophores in cellulosics. Due to its special resonance stabilization, it is a prime survivor of bleaching treatments and its degradation is essential in pulp bleaching. The clarification of the degradation mechanism of this compound is indispensable for targeting improvements of pulp bleaching processes. Previous studies revealed that DHBQ degradation by hydrogen peroxide (H2O2) is influenced by salts. This study addresses the effects of alkaline metal salts, alkaline earth metal salts, and Al2(SO4)3 on the degradation of DHBQ under simulated conditions of pulp bleaching in a peroxide stage. The degradation by excess H2O2 followed first-order kinetics in the presence of alkaline metal salts and alkaline earth metal salts, which enhanced and retarded the reaction, respectively. Kinetic studies and theoretical computations provided detailed mechanistic insights: Li+, Na+, and K+ stabilize several reaction intermediates by complex formation, causing the enhancement of the degradation, whereas Mg2+ and Ca2+ coordinate and stabilize the reactant, resulting in the observed retardation. Al2(SO4)3 exhibited a strong enhancing effect, but the degradation followed second-order kinetics with regard to DHBQ, suggesting a fundamentally different degradation mechanism.

The lack of simple differentiation of all-polysaccharide-film components in nanoscale hinders unveiling their structure-property dependency. Submicron hierarchy of films of cellulose nanofibrils (CNFs) and carbohydrate-based additives was revealed via visualization of the components by their differentiating adhesion to an Atomic Force Microscope (AFM) tip. The differentiation of the film components revealed that distribution of hydroxypropylated hemicellulose in the CNF matrix could be tuned by addition of a plasticizer. The hemicellulose hydroxypropylation degree of substitution (DS) was detected to be another parameter affecting the film structure due to the water-solubility depending on the DS. This was further verified via Quartz Crystal Microbalance with Dissipation Monitoring (QCM-D). The translucent, self-standing films comprising CNFs, sorbitol and hydroxypropylated hemicellulose were tested for mechanical, optical and oxygen diffusion performance. The performance was linked to their structural evenness, which confirmed that the oxygen diffusion through the film is tremendously affected by the film nano hierarchy.

5,8-Dihydroxy-[1,4]-naphthoquinone (DHNQ) is one of the key chromophores in cellulosic materials. Its almost ubiquitous presence in cellulosic materials makes it a target molecule of the pulp and paper industry’s bleaching efforts. In the presented study, DHNQ was treated with hydrogen peroxide under alkaline conditions at pH 10, resembling the conditions of industrial hydrogen peroxide bleaching (P stage). The reaction mechanism, reaction intermediates, and final degradation products were analyzed by UV/vis, NMR, GC–MS, and EPR. The degradation reaction yielded C1–C4 carboxylic acids as the final products. Highly relevant for pulp bleaching are the findings on intermediates of the reaction, as two of them, 2,5-dihydroxy-[1,4]-benzoquinone (DHBQ) and 1,4,5,8-naphthalenetetrone, are potent chromophores themselves. While DHBQ is one of the three key cellulosic chromophores and its degradation by H2O2 is well-established, the second intermediate, 1,4,5,8-naphthalenetetrone, is reported for the first time in ...