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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.

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.

The use of recovered paper in the paper and board industry worldwide has increased in the last decade. The recycling process affects several properties of the paper, so recovered pulp needs to be enriched with a certain amount of virgin fibre to increase the strength and quality of the paper, and thus the quality of the print. Since the cellulose-based printing substrates are sensitive to photolytic damage caused by exposure to light and high temperature, the focus of the research was to evaluate the stability of digital UV inkjet prints on laboratory substrates with wheat pulp. Assessment of the optical stability of laboratory substrates and prints made on them after ageing treatment was based on the reflectance spectra measurements before and after artificial ageing. In order to observe the optical changes that occur in cellulose printing substrates, unprinted and digital printed substrates were placed in an artificial ageing equipment SunTEST XLS+ test chamber according to standard ASTM D 6789-02. The test chamber emits visible and near ultraviolet electromagnetic radiation in the range from 290 nm to 800 nm. With the deterioration of the optical stability of unprinted and digital printed substrates, it was observed through the reflectance spectra (R) and the Euclidean colour difference (ΔE00*) that the highest colour degradation of all analyzed samples, occurs in the first 48 hours of artificial ageing. The results of this analysis confirm that the addition of wheat pulp in paper pulp provides better optical stability of unprinted and digital printed laboratory substrates.

Wood is still the most widely used raw material for pulp and paper production in the world. However, due to the necessity to supply the paper industry with raw materials used in the extraction of cellulose fibres and the overexploitation of forests, new sources of primary pulp fibres had to be identified. The aim of this research is to highlight the important features of cereal crop residues and their utilization in the paper industry. As the chemical composition of plant materials is one of the most important indicators of how such materials can be used in paper production, the analysis of the chemical composition of straw with the highest grain production was performed. The straw, as a harvesting residue, is a fibre resource available from the annually renewable crops, produced abundantly in numerous regions all over the world. For the purpose of the research, wheat, triticale and barley straw were selected for the analysis. The analysis of carbohydrate, lignin and extraneous material (organic extractives and inorganic minerals) was performed in order to obtain the straw chemical composition. Based on the results of the chemical composition of all analysed straw, it was confi rmed that straw, as an agricultural by-product, is rich in cellulosic fi bres and, therefore, a valuable raw material for the paper industry. Out of all analysed straw, based on the results of their chemical composition, triticale straw is considered potentially the best source of alternative cellulose fibres., Drvo je još uvijek najčešća sirovina za proizvodnju celuloze i papira u svijetu. Međutim, s obzirom na količinu sirovine za izdvajanje celuloznih vlakanaca potrebnih papirnoj industriji te na prekomjernu eksploataciju šuma, nužno je pronaći nove izvore primarnih celuloznih vlakanca. Cilj ovog istraživanja bio je istaknuti važnost slame koja je kao poljoprivredni ostatak prikladna sirovina za industriju papira. Kako je kemijski sastav biljnog materijala jedan od najvažnijih razloga njegove upotrebe u proizvodnji papira, određen je kemijski sastav slame žitarica s najvećim doprinosom zrna. Slama, kao ostatak nakon žetve, godišnje je obnovljiv izvor vlakanaca u mnogim regijama diljem svijeta proizvodi u izobilju. Za ovo je istraživanje izabrana slama pšenice, pšenoraži i ječma. Obavljena je kvantitativna analiza ugljikohidrata, lignina i ekstraktivnih tvari (organski ekstrakti i anorganski minerali) kako bi se odredio kemijski sastav slame žitarica. Na temelju kemijskog sastava svih analiziranih slama potvrđeno je kako je slama kao poljoprivredni nusproizvod bogat izvor celuloznih vlakanaca, a time i vrijedna sirovina za industriju papira. Od svih analiziranih uzoraka slama pšenoraži svojim se kemijskim sastavom nametnula kao najveći potencijalni izvor alternativnih celuloznih vlakanaca.

Wood is still the most widely used raw material for pulp and paper production in the world. However, due to the necessity to supply the paper industry with raw materials used in the extraction of cellulose fibres and the overexploitation of forests, new sources of primary pulp fibres had to be identified. The aim of this research is to highlight the important features of cereal crop residues and their utilization in the paper industry. As the chemical composition of plant materials is one of the most important indicators of how such materials can be used in paper production, the analysis of the chemical composition of straw with the highest grain production was performed. The straw, as a harvesting residue, is a fibre resource available from the annually renewable crops, produced abundantly in numerous regions all over the world. For the purpose of the research, wheat, triticale and barley straw were selected for the analysis. The analysis of carbohydrate, lignin and extraneous material (organic extractives and inorganic minerals) was performed in order to obtain the straw chemical composition. Based on the results of the chemical composition of all analysed straw, it was confi rmed that straw, as an agricultural by-product, is rich in cellulosic fi bres and, therefore, a valuable raw material for the paper industry. Out of all analysed straw, based on the results of their chemical composition, triticale straw is considered potentially the best source of alternative cellulose fibres., Drvo je još uvijek najčešća sirovina za proizvodnju celuloze i papira u svijetu. Međutim, s obzirom na količinu sirovine za izdvajanje celuloznih vlakanaca potrebnih papirnoj industriji te na prekomjernu eksploataciju šuma, nužno je pronaći nove izvore primarnih celuloznih vlakanca. Cilj ovog istraživanja bio je istaknuti važnost slame koja je kao poljoprivredni ostatak prikladna sirovina za industriju papira. Kako je kemijski sastav biljnog materijala jedan od najvažnijih razloga njegove upotrebe u proizvodnji papira, određen je kemijski sastav slame žitarica s najvećim doprinosom zrna. Slama, kao ostatak nakon žetve, godišnje je obnovljiv izvor vlakanaca u mnogim regijama diljem svijeta proizvodi u izobilju. Za ovo je istraživanje izabrana slama pšenice, pšenoraži i ječma. Obavljena je kvantitativna analiza ugljikohidrata, lignina i ekstraktivnih tvari (organski ekstrakti i anorganski minerali) kako bi se odredio kemijski sastav slame žitarica. Na temelju kemijskog sastava svih analiziranih slama potvrđeno je kako je slama kao poljoprivredni nusproizvod bogat izvor celuloznih vlakanaca, a time i vrijedna sirovina za industriju papira. Od svih analiziranih uzoraka slama pšenoraži svojim se kemijskim sastavom nametnula kao najveći potencijalni izvor alternativnih celuloznih vlakanaca.

For paper industry and consequently graphic industry it is very important that fibres used in paper production provide high quality and printability of the paper. In pulp and paper industry fibres of cellulose pulp derived still predominantly from wood, but in the last few years the consumption of non-wood raw materials for that purpose has grown. This work presents research on the chemical stability of printed hemp fibre based papers to water, alcohol and alkali. Evaluation of chemical degradation on prints was determined through the spectro-photometric measurements. Deviations in colour of prints have shown that highest chemical stability provides prints made on industrially paper formed from mixture of hemp and post-consumer fibres with high share of inorganic components. Further, bleached hemp fibres in handmade 100 % hemp fibre based paper give prints with the lowest chemical stability.

This paper presents the study results of performance and efficiency of fresh offsetprinted Croatian daily newspaper, deinked by means of novel chemistry, named Eco-alkali. Eco-alkali is naturally gained alkali prepared from domestic by-product wood fly ash collected after hardwood ignition. Brightness, opacity and effective residual ink concentration (ERIC) as optical properties were evaluated for the deinked pulp before and after flotation. Lingering ink particles and their total surface area were measured by means of image analysis method. Experimental results are compared to the pulp deinked with worldwide accepted method INGEDE Method 11, using identical steps through the whole deinking process. The insights obtained from present work, especially removing particle efficiency results before flotation, indicated that eco-alkali have potential to be used in flotation deinking of newspapers.