In recent years, due to environmental awareness regarding the harmfulness of polymeric materials, there has been a growing interest in using papers, especially those from alternative raw materials. ...The importance of using all available raw materials is imperative today. Raw materials that were once viewed as waste are now of great importance because they have the ability to replace raw materials that are used irrationally or are lacking. Cereal straw is a lignocellulosic material that could be used in the paper industry and in the production of increasingly prevalent paper packaging. The aim of this research was to analyze the relationships between the qualitative parameters of straw-based printed papers containing 30% agricultural residues (wheat, barley, or triticale). The influence of two qualitative parameters (ink penetration depth and optical ink density) on the print-through was observed using multiple regression analysis on straw-based papers produced at the laboratory level. Throughout the research, 100% recycled wood paper was used as a reference sample. The results of the regression analysis showed that none of the variables individually make a statistically significant contribution to the prediction of the dependent variable in a linear context, that is, they indicate a non-linear interaction between the variables and the specific conditions under which the dependent variable reaches local extremes and changes in the gradient. Considering the results of the regression analysis and the visualization of the relationship, the model was additionally tested with other independent variables (paper type). From the results obtained, it can be concluded that the alternative straw-based paper with 30% barley pulp has the best interaction between ink and paper, which is the most similar to the reference sample in terms of printability, while the alternative straw-based paper with 30% wheat generally differs significantly from the reference paper when all three prints are considered.
Natural ageing has a major influence on the properties of paper, while light, heat, and humidity are the environmental influences that most disrupt the stability of paper. This research focuses on ...changes in straw-containing papers caused by accelerated ageing. The papers were made in the laboratory by mixing straw pulp with the pulp of recycled fibers in different weight ratios and were artificially aged by a dry-heat treatment (thermal oxidation) and UV radiation treatment (photo-oxidation) over a 24 h period to simulate natural ageing. The observed changes in the optical, surface, and chemical stability of papers were analyzed and are discussed in this paper. It is evident that, regardless of the origin of straw for pulp production, it forms papers that undergoes similar optical properties (photo-yellowing and brightness lose), while certain differences have been observed in surface and chemical stability. Based on all analyses performed as part of this research, it was found that paper produced with the addition of wheat pulp is the most stable of all laboratory straw-containing papers. However, it must be emphasized that, if lignin-containing straw pulp is used as the main constituent of paper, the brightness stability of such pulp must be improved, or the paper surface must be improved by surface finishing in order to obtain greater stability against ageing.
Paper performance qualities strongly depend on the origin of cellulose fibers. Awareness of environmental issues and sustainable development has led to the increase in the use of recycled printing ...papers. Recovered fibers are often used as a substitute for virgin wood fibers in the production of certain types of papers. As recovered fibers cannot provide the same quality level of paper products as virgin wood fibers, alternative sources of virgin cellulose fibers need to be identified. The aim of this research was to analyze the printability of laboratory papers made of different contents of straw pulp. Therefore, the printing papers were formed using straw pulp of three different cereal species (wheat, barley, and triticale) and mixing them with recycled newsprint in different weight ratios. The printability of these laboratory papers was analyzed by classifying dot reproduction quality based on four dot reproduction attributes. Printed dot reproduction greatly affects the quality of reproduction in graphic products, as dots are the most important element in multi-color reproduction of texts and images. It was confirmed that laboratory papers containing straw pulp provide the same or even better dot reproduction quality than laboratory control papers formed only of recycled newsprint.
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Paper is one of the most important materials for packaging and the demand for
this material is constantly increasing. The printing and packaging
industries are researching alternative sources of ...fibre, to produce more
environmentally friendly paper without compromising quality. As a packaging
material, paper must meet high strength requirements, and it has to exhibit
acceptable surface properties to preserve the printing quality. This
research had two objectives: to produce paper made from pulp of recycled
fibre reinforced with virgin straw fibre and to evaluate the print quality
on such papers. Straw pulp used for this purpose was obtained from three
cereal crops: wheat, barley, and triticale. The paper produced was printed
by using five printing techniques. Rubbing stability was evaluated by the
difference in colour and reflectance spectra before and after performing rub
tests and a comparison was made for the best interaction of paper and ink
determined by the printing technique. For the prints with the highest colour
difference after the rub test, the surface of the rub test receptor
(uncoated recycled paper) was examined for signs of ink transfer during the
test and the areas of transferred ink coverage were calculated on their
processed microscopic images.
The use of non-wood fibres for paper production could be one of the most environmentally friendly and economical alternatives. Reducing the consumption of wood pulp in paper and cardboard production ...by replacing wood pulp with alternative plant biomass could be a viable solution, as the amount of non-wood fibres in biomass is far from being exhausted. In this study, straw from the most commonly grown agricultural crops in Croatia was used as a source of non-wood fibres. Agricultural residues from wheat, barley and triticale were selected as a substitute for wood fibres for the production of laboratory papers with straw fibres. Under laboratory conditions, straw pulp was mixed with recycled wood pulp in a ratio of 30:70 to produce paper sheets that can be printed with different printing techniques. Regardless of the printing technique used, it is desirable that the prints contain a high-quality reproduction of the image and text on the surface of the paper and that the ink does not penetrate completely through the substrate. In this context, this study observed the use of laboratory-made papers with non-wood fibres as the printing substrate by analysing the maximum depth of ink penetration into the printing substrate obtained with two printing techniques - a modern one (digital UV inkjet) and a very high quality conventional one (gravure). It was found that the gravure printing favoured a greater penetration of the UV ink into the substrate with the addition of straw pulp compared to the digital printing technique. However, this is a consequence of the printing technique, as similar ink penetration was also observed on the laboratory substrate made only from recycled fibres. Compared to commercial papers, the ink penetration is slightly higher into the laboratory made printing substrates. It is interesting to note that the printing substrate with the addition of 30% triticale pulp has the lowest ink penetration, especially in multicolour prints produced with the digital UV inkjet printing technique.
From the moment of production, paper as a printing substrate is exposed to the process of natural ageing regardless of the type of cellulose fibres in its composition. Accordingly, the prints ...produced by the various printing techniques are also exposed to several factors that impair the quality of the print i.e. its colour over time. Therefore, it is very important to properly select the printing substrate for achieving a high quality of graphic products. For that purpose, three types of papers with hemp fibres were used as printing substrates which were printed with laboratory hand-operated instrument Esiproof using flexographic cyan (C), magenta (M), yellow (Y) and black (K) water-based inks. Prints were artificially aged in SunTEST XLS+ test chamber according to standard ASTM D 6789-02 for 48 and 96 hours. Based on changes in the reflectance spectra of each printed ink after exposure to electromagnetic radiation it was noticed how composition of printing substrate strongly influence on colour stability of prints due time. An increase of exposure time to electromagnetic radiation leads to a decrease in the value of the reflectance of the printing substrate and cyan, magenta and yellow prints. It was confirmed how electromagnetic radiation have the greatest impact on the reflectance of yellow print, while the black one is the most stabile regardless of the substrate it was printed on.
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Surface characteristics of printing substrates are of the utmost importance to all types of paper that interact with ink. During all types of printing processes, the behaviour of the liquid phase ...(ink or dye) on the paper is directly defined by the paper cellulose-based surface. The printed ink spreads and penetrates more into paper fibres when the paper surface is rougher and more permeable. Contact angle measurements by sessile drop method are considered the most appropriate for determining the paper sheet surface energy. Paper as hydrophilic material has a high absorption rate resulting in a low contact angle. The objective of this study was to evaluate the surface free energy of laboratory-made papers containing straw pulp obtained from residues after the harvest of the most cultivated cereals in Croatia (wheat, barley and triticale). The obtained surface free energy results are promising for straw pulp usage in the manufacture of printing paper.
Nowadays, there is a strong initiative to use recycled or biodegradable materials in all aspects of production including the graphic industry. In this study, paper was used as a material fulfilling ...the two of mentioned properties. Under laboratory conditions, papers were made of 70% pulp from recycled wood fibres with an addition of 30% straw pulp (wheat, barley or triticale). Considering the importance of the possibility of printing such media based on their end use, the influence of fibre type on vapour barrier properties was studied and overall migration to hydrophilic and fatty food simulants was measured. Analyses were performed on digital, flexographic, and offset prints obtained by printing laboratory papers with UV-curable black ink. It was found that prints produced using the offset technique, in which the ink remains on the surface of the paper, had lower overall levels of migration compared to other printing techniques. The paper produced appears to have the potential to be used as a secondary food packaging material.
This research observes changes in the properties of commercially available hemp office papers exposed to photo-oxidation for artificial aging. In order to accelerate the changes that naturally occur ...in paper, photo-oxidation was performed using a Xenon light source. The electromagnetic radiation was administered in doses of 550?W/m2 over 24 hours with a temperature of 60°C. Three types of hemp office papers that differ in chemical composition and manufacturing process were used as samples. The strength properties (tensile index, elongation at break, tear index), surface properties (Bendtsen roughness, Bekk smoothness), pH of paper extracts, and optical properties were observed. The listed properties of artificially aged samples were compared to those of unaged commercial paper samples. The results show that, after only 24 hours, accelerated aging with a Xenon arc lamp affects all observed paper properties. For all analyzed office papers, the values of the tensile index, Bekk smoothness, and pH of paper extracts decreased, while the values of elongation break, tear index, and Bendtsen roughness increased due accelerated aging. Regarding the CIE L*a*b* color space value, lightness (L*) generally decreased after the aging treatment, and all paper samples became less reddish (a* decreased) and more yellow (b* increased). The obtained results of this research reveal that pulp with hemp fibers can produce higher-quality office paper that is more stable against light and temperature influences than those made with post-consumer fibers. However, to increase the durability of manufactured paper, hemp fibers must be bleached.
The aim of this research has been to demonstrate the use and applicability of substrates containing non-wood fibres in the printing industry, with an emphasis on flexographic printing for packaging. ...To obtain such substrates, laboratory papers were produced with the addition of 30% non-wood fibres (wheat, barley and triticale), in combination with recycled wood pulp. These substrates were tested for chemical and mechanical resistance after flexographic printing with conventional and ultraviolet curing inks. The results showed that all laboratory papers with the addition of 30% non-wood fibres, printed with water-based inks, had fairly good chemical and mechanical resistance, except for the prints treated with sodium hydroxide. Thus, such papers should not be used as packaging materials for alkaline products. UV-curable inks on these substrates showed low chemical resistance, thus should only be used on substrates intended for secondary packaging. The mechanical resistance of UV prints was very good, thus papers containing straw pulp could be used for various applications.
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