Pulp and paper
Jafar Ebrahimpour Kasmani; Ahmad Samariha
Abstract
Background and objectives: Fruit packaging cardboard protects fruits from impacts, pressure, and damage during transportation, while helping to maintain their freshness and quality. To achieve these objectives, it is essential to enhance the strength of the cardboard and minimize the interaction between ...
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Background and objectives: Fruit packaging cardboard protects fruits from impacts, pressure, and damage during transportation, while helping to maintain their freshness and quality. To achieve these objectives, it is essential to enhance the strength of the cardboard and minimize the interaction between its interior and exterior. At the same time, it must be biodegradable, durable, and environmentally friendly. Kraft paper is recognized as a suitable option for preserving the quality of fruits. Therefore, this research aims to improve the barrier and mechanical properties of cardboard by applying coatings of nano-graphene, fluorine, and zein, both separately and in combination, to provide consumers with higher quality cardboardMethodology: The brown kraft liner paper with a basis weight of 120 grams was obtained from the Mazandaran Wood and Paper Company. The nanographene type AO-4 was sourced from Graphene Supermarket in the USA, zein protein from Sigma Aldrich, and fluorine from Mine Kavaran Production Group. For coating, the nanographene, zein, and fluorine were weighed in specified weight percentages and mixed with 100 grams of distilled water for 30 minutes at 50 degrees Celsius, depending on the treatment conditions. Then, 2.5 grams of styrene-butadiene latex and 0.5 grams of dispersant D200 were added to the mixture and homogenized for 20 minutes at 1500 RPM. A 5% cationic starch solution was also added as a retention aid to enhance the coating. The coating solutions were applied to the paper sheets using an Auto Bar Coater (GBC - A4 GIST Co., Ltd). The physical and mechanical properties were measured according to TAPPI and ISO standards. The experimental design was completely randomized, and data analysis was performed using one-way ANOVA and Duncan's test at a 95% confidence level.Results: The one-way ANOVA analysis indicated that there are significant differences at the 5% level among the thickness, water absorption, and porosity of the 8 types of paper. The greatest thickness was observed in the brown liner paper coated with graphene and fluorine, while the lowest thickness was found in the control sample, with a difference of 27% between the maximum and minimum thickness. The lowest water absorption was noted in the brown liner paper coated with zein, fluorine, and nano-graphene, with a difference of 647.5% between the maximum and minimum water absorption. Additionally, the least porosity was attributed to the paper coated with nano-graphene, showing a difference of 7365.8% between the maximum and minimum porosity. Density analysis revealed that the highest density was observed in the sample coated with zein and nano-graphene, with a difference of 14.5% between the maximum and minimum density. Furthermore, the highest surface smoothness was recorded in the paper coated with nano-graphene and zein, with a difference of 23.9% between the maximum and minimum surface smoothness. For the tensile and tear resistance index, no significant difference was observed at the 5% level, with differences of 15.5% and 26.4% between the maximum and minimum tensile and tear resistance indices, respectively. However, for burst resistance, the lowest value was found in the paper coated with fluorine and zein, with a difference of 14.2% between the maximum and minimum burst resistance. In terms of ring crush test, the highest resistance was related to the paper coated with zein, fluorine, and nano-graphene, with a difference of 16.1% between the maximum and minimum ring crush test.Conclusion: The goal of food packaging is to extend shelf life and protect against spoilage factors. Paper and cardboard, as packaging materials, have specific advantages and disadvantages, including a lack of resistance to moisture. This research addresses the improvement of the physical and mechanical properties of kraft liner paper for fruit packaging and has demonstrated that coating increases thickness and reduces water absorption. These coatings enhance the prevention of water absorption by penetrating the pores of the paper. Various factors affect water permeability, including the paper structure and the type of coating. The use of nano-graphene and zein leads to a reduction in paper porosity and an improvement in its mechanical properties. In this study, coating the paper with nano-graphene and zein significantly increased barrier properties and improved paper quality. Additionally, the results indicate that these compounds can help reduce water absorption and porosity of the paper.
Pulp and paper
Jafar Ebrahimpour Kasmani; Ahmad Samariha; Alireza Khakifirooz
Abstract
Background and objectives: Waste paper recycling has grown as an industry in Iran and the world and offers many benefits to the environment and humans. Municipal waste is also reused after recycling processes. Cardboard recycling industry has great environmental and economic importance and with the lack ...
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Background and objectives: Waste paper recycling has grown as an industry in Iran and the world and offers many benefits to the environment and humans. Municipal waste is also reused after recycling processes. Cardboard recycling industry has great environmental and economic importance and with the lack of wood resources and high demand for paper products, it plays an important role in the development of paper-related industries. However, recycling can be associated with a reduction in the optical properties of the paper. The use of nanoparticles in the paper industry is also expanding day by day. Nanosilica is one of the most important nanoparticles used as a retention aid in the paper industry. In order to reduce the consumption of long fibers and obtain the desired optical properties, the use of nanosilica alone or in combination with other materials such as cationic starch and cationic polyacrylamide is investigated. The purpose of this research is to compare the effect of separate and combined use of nanosilica additives, cationic polyacrylamide, cationic starch and long fibers on the optical properties of white liner paper pulp.Methodology: In this study, white paper pulp with a brightness of at least 78% and a gloss of at least 45% was used to prepare handmade papers. Long fiber chemical paper pulp from coniferous kraft imported from Russia with a brightness of 89% was used in the laboratory. Nanosilica powder (NanoSiO2) produced by Degussa, Germany, cationic polyacrylamide with Farinret K325 brand, produced by Degussa, Germany, and cationic starch from LyckebyAmylex, Slovakia, were used. Independent treatments include the addition of 10% refined long fibers paper pulp, 6% nanosilica, 1.5% cationic starch and 0.15% cationicpolyacrylamide and combined treatments include 6% nanosilica and 1.5% cationic starch and 6% nanosilica and 0.15% cationic polyacrylamide. Then 127 g.m-2 handmade papers were prepared and their optical and microscopic properties were evaluated.Results: The results showed that by adding 10% of long fibers, the brightness decreased and by using 6% of nanosilica, the maximum brightness was obtained. Meanwhile, the whiteness of papers with 6% nanosilica was minimum and maximum with 0.15% cationic polyacrylamide. Opacity showed its highest value with the combination of 6% nanosilica and 0.15% cationic polyacrylamide. Also, by increasing the amount of polyacrylamide and cationic starch, individually or in combination with nanosilica, the opacity increased. The light absorption coefficient was the lowest in papers with 6% nanosilica and the light scattering coefficient was the highest in papers containing 6% nanosilica and 0.15% cationic polyacrylamide. A colorimeter was used to measure the color components and the results showed that the additives had an effect on the brightness and whiteness of the papers. Also, changes in the color spectrum and the amount of color change were also observed. Additives increased the darkness and changes in different colors.Conclusion: The use of nanosilica separately and in combination with starch and cationic polyacrylamide increases the brightness of papers. Also, the use of cationic polyacrylamide separately and in combination with nanosilica leads to an increase in the whiteness and opacity of papers. The brightness factor of the papers, which is representative of the L* component, decreased with the exception of the addition of 10% long fibers and 6% nanosilica. The amount of overall color change with ∆E* was the lowest in samples containing 1.5% cationic starch and the highest in samples containing 0.15% cationic polyacrylamide. The use of some treatments can lead to a decrease in the optical properties and a decrease in the printability quality of the white liner. To solve this problem, mechanical paper pulp that has been decolorized or coated on the surface of the paper can be used. The presence of nano-silica particles in the structure of the paper improves the bond surface and reduces the prosity, which results in the reduction of surface roughness and less light refraction, and increases the light reflection and brightness of the paper.
