مجله تحقیقات علوم چوب و کاغذ ایران
سال سی و نهم شماره 4 (پیاپی 89، زمستان 1403)

Plastic packaging is considered one of the most important sources of environmental problems due to its slow decomposition. To address this issue, biomaterials have garnered attention for their quick decomposition and renewability. In this context, the use of cellulose fibers in packaging is preferred over plastic. However, the main challenge of using cellulose fibers in packaging production is their poor water resistance. This issue can be improved with a suitable bio-coating, which has inspired the current study. The aim of this study was to use a simple method to prepare hydrophobic paper that is environmentally friendly with a biopolymer.

The raw material used to make handsheets was bleached softwood Kraft pulp from the Pars paper mill. The Canadian Standard Freeness (CSF) of refined paper decreased from 750 ml CSF to 350 ml CSF. To enhance strength properties, the fibers were treated with carboxymethylcellulose (CMC) in the presence of electrolyte (CaCl2). A suspension of untreated (70%) (LF) and CMC-treated (30%) cellulose fibers was used to make handsheet paper (MLF) with a grammage of 60 g/m2. To prepare the emulsion, beeswax was melted in hot water at different concentrations (1, 5, 10, 15, and 20%), then dispersed in water using ultrasound for 9 minutes with an amplitude of 100. The paper was air-dried, immersed in different concentrations of beeswax emulsion, and then heat-treated at various temperatures (25, 60, 70, 80, and 90 ⁰C). The effect of thermal treatment on the efficiency of beeswax was examined by measuring water absorbency time and water contact angle for all treatments, with 70 ⁰C identified as the optimal temperature. The next step is to evaluate the effect of different concentrations of beeswax on properties such as water absorption (cobb), thickness, grammage, tensile strength index, brightness, and opacity.

Compared to untreated paper, the water absorbency time and water contact angle of all paper treated with different concentrations of beeswax at various temperatures (25, 60, 70, 80, and 90⁰C) increased significantly. The contact angle of handsheets treated with beeswax increased significantly with the temperature of thermal treatment. The highest water contact angle was achieved with handsheets immersed in 20% beeswax and heat-treated at 70 ⁰C. However, further increases in temperature beyond 70 ⁰C did not significantly affect the water contact angle of the paper samples. The water absorption in LF and MLF papers was 65.96 g/m2 and 7.96 g/m2, respectively. Treatment with beeswax reduced the water absorption rate compared to the control treatment at all concentrations. Paper coating increased the thickness and grammage of the paper, which increased with higher concentrations of beeswax emulsion. The tensile strength index increased after using modified fibers with CMC compared to LF paper, but coating with beeswax emulsion decreased the tensile strength index of the paper. MLF treatment and beeswax-coated paper had higher brightness compared to LF paper. Immersion in beeswax slightly decreased opacity, but this change was not statistically significant.

The results indicate that the barrier characteristics in samples covered with beeswax improved compared to the blank sample. The study demonstrates the efficient, simple, and cost-effective production of hydrophobic paper as a biodegradable material. A key advantage of this method is the absence of chemicals containing flora or organic solvents in the preparation, making it suitable for industrial applications and meeting the requirements for sustainable development through the use of green ingredients.

Many studies have been conducted on the use of cellulosic resources to provide portion of raw materials for wood and paper industries. Waste branches for some species such as palm and Prosopis cineraria in southern parts of country can be a solution for deficiency of raw material in wood and paper industries. This study investigated the possibility of using a combination of Prosopis cineraria and industrial wood particles to produce particleboard with acceptable physical and mechanical properties.

The variables in this study were the ratio of Prosopis cineraria to industrial wood particles at four levels (0:100, 15:85, 30:70, 45:55) and urea formaldehyde resin at two levels (10 and 12 percent). Industrial wood particles from Sanate Choube Shomal Company and Prosopis cineraria particles were obtained from the province of Sistan and Baluchistan. Ammonium chloride as a hardener was used at 2 percent of the dry weight of the adhesive. After mixing raw material, the mat was placed under hot pressing at a temperature of 170 ˚C for 6 minutes. After the manufacture of the single-layer particleboard, the physical and mechanical properties of the boards were analyzed by a factorial test in a completely randomized design with a confidence level of 5%.   

The results showed that the physical and mechanical properties of the panels decreased as the percentage of mixture Prosopis cineraria particles increased. So that, panels containing 45% Prosopis cineraria particles and 10% urea-formaldehyde resin had the lowest mechanical properties, while panels containing 12% urea-formaldehyde resin without Prosopis cineraria s particles had the best mechanical properties. Panels containing 45% Prosopis cineraria particles and 12% urea-formaldehyde resin had the lowest water absorption and thickness swelling, while panels containing 10% urea-formaldehyde resin without Prosopis cineraria particles had the highest.

According to the results of this study, there was usability of boards with 15% Prosopis cineraria particles and 10% resin for Type P1 boards and the boards with 15% Prosopis cineraria particles and 12% resin for Type P2 boards.

 The Covid-19 pandemic caused serious challenges to various industries of wooden products in various aspects such as access to raw material, supply chain, production and sales volume of product and even customer preferences. Therefore, this study aims to investigate the mediating role of government support in relation to revising some adopted policies such as investment strategies, creating resilience in industries and improving financial knowledge of managers of these industries in order to increase production of various wooden furniture products in the post-corona era was done. In terms of its nature, this research is fundamental-applied and in terms of the type of research, it is a part of mixed research including quantitative and qualitative variables.The study population consisted of 180 managers of home and office furniture manufacturing companies based in Tehran and Alborz provinces, from which 120 were selected through the Cochran formula. Field-library methods are used to collect preliminary information as needed, the main tool for collecting information for this research is a questionnaire approved by academic experts. The used questionnaire includes 22 questions related to research variables, including resilience, government support as a moderating variable, investment strategies, financial knowledge and production growth. Also, the scale used is a 5-point Likert scale. In this research, Cronbach's alpha coefficient, composite reliability and extracted average variance were used to determine the reliability and convergent validity of the questionnaire. In order to analyze the internal structure of the questionnaire and discover the constituent factors of each structure or variable, the confirmatory factor analysis tool was used. Also, to check and analyze the data, descriptive and inferential statistics were used using SPSS software, and to check the relationships between variables, structural equation method based on the use of Smart-Pls software was used. The results of correlation between the variables show that at a significance level of 1%, the highest correlation is between financial knowledge variables with investment strategies, and the lowest correlation is between government support variables with production growth. Also, the reliability check of the questionnaire shows that there is reliability and convergent validity in the questions. The results of examining the measurement model using confirmatory factor analysis show that the items of the model are correctly defined and it is not recommended to remove any of them, because the values ​​of the factor loadings are higher than the minimum acceptable value, i.e. 0.3. This study showed that there is a positive and significant relationship between investment strategies, resilience and financial knowledge as independent variables and positive growth as a dependent variable. Research findings show that the government support component is also related to production growth. It has a positive and significant relationship. In relation to the role of government support as a mediating variable in the relationship between investment strategies, resilience and financial knowledge on production growth of wooden furniture industry, the results show an effective relationship. In all these research hypotheses, the significance level of the p-value test is less than 5% and the T value is outside the range (1.96, -1.96), so it is significant with a 95% confidence factor. The results of this research revealed that in the post-corona era, wooden furniture industry may face new developments and changes. These changes can include changes in the needs and tastes of customers, the process of marketing and selling products, the use of environmentally friendly products, changes in the structure of companies and the necessity of creating industrial holdings, the necessity of using new technologies in production of various products in furniture industry and decoration, paying more attention to firm's internal structures to increase the level of resilience, using managers with extensive financial knowledge to deal with fluctuations of firm's financial assets. Also, in the post-corona era, government support for wooden furniture industries can play an important role in impact of investment strategies, resilience and financial knowledge on production growth of these industries.

Today, with the rapid development of human society, the pollution of particles matter (PM) in the atmosphere has increased. Suspended particles easily enter the human respiratory system and have serious effects on health, they are considered as one of the critical and risky issues in modern urban societies. Air filters play a key role in reducing the emission of these particles and preventing their harmful effects on human health. Due to the growing importance of air pollution and its harmful effects on human health and the environment, the use of effective and environmentally friendly filters has received more attention. In this regard, natural and biodegradable materials such as bamboo fibers are considered a suitable alternative to synthetic polymer materials in making filters. This research focuses on the preparation and evaluation of cellulose air filter using bamboo fibers to deal with air pollution.

To prepare the filter, bamboo fibers were first pulped through the process of soda anthraquinone with 25% sodium hydroxide, pulping time 2 hours and temperature 175 degrees Celsius with 0.2% anthraquinone (AQ), then during D0ED1 sequence was bleached by chlorine dioxide and soda. In the next step, the oxidation process was carried out with 3% hydrogen peroxide, 3% sodium silicate and the ratio of sodium hydroxide to hydrogen peroxide 0.8. Then 3% polyvinyl alcohol was added to the resulting suspension and stirred for 10 minutes with the same retention time for all treatments. The suspension was homogenized with an Ultra Thorax homogenizer and dried in a freeze dryer at -110°C for 72 hours to prepare the cellulose filter.

The results showed that oxidation and addition of PVA have a positive effect on the mechanical and structural characteristics of the filter. The tensile strength of filters improved significantly after oxidation and adding PVA and increased from 0.236 Nm/g to 0.528 Nm/g. The amount of porosity and air permeability were also affected by oxidation and PVA addition, after oxidation, the porosity and air permeability increased by increasing the number of carboxyl groups and improving the dispersion of cellulose fibers. While the addition of PVA created strong hydrogen bonds and reduced porosity and air permeability. Electron microscopic images (SEM) also clearly showed the structural changes caused by oxidation. After oxidation and adding PVA, the density of the fiber network increased and improved the uniform dispersion of fibers and created a more coherent structure while small pores between fibers still existed. The specific surface area and the average pore size of the filters were checked using the BET method, which shows that the specific surface area increased in the oxidized and PVA-containing filters, and the pore size was maintained in the nano scale in all filters.

These results show that the combination of oxidized bamboo fibers containing PVA leads to the production of efficient air filters with improved characteristics that can help reduce air pollution because these filters are able to prevent the passage of PM suspended particles by having pores at the nanoscale.

 In the present era, technological advancement depends on the progress made in the field of materials and the production of composites has been a significant step towards the evolution of engineering materials. By physically combining two or more materials, not only lighter and stronger material are produced, but such new materials replace the traditional materials. This research aims to compare the mechanical and physical properties of composites coated with small glass beads and shells powder, individually and in mixture, and to select the best sample with lighter specific weight, better strength, and easier installation for building facades.

 The samples were prepared using beech wood flour, E-grade glass fibers, ortho unsaturated polyester resin matrix, montmorillonite K10 nanoclay, MEPK, 10% cobalt as a constant factor, Caspian Sea rolling shell (Cerastoderma glaucum) powder, and small glass beads as a variable factor. Specimens were made using the hand lay-up method. Variable percentages of glass beads and shells, or a combination of both, were used on the composite as a gel coat. Fifteen composite blocks with dimensions of 20×30×0.7 cm3 were prepared. The edges of the block were then sanded. The blocks were placed in an oven at 120 degrees centigrade for 2 hours, and after cooling, they were weighed and their dimensions were measured, and then cut to the required sizes, and physical and mechanical properties such as water absorption, thickness swelling, bending, tension, impact, and abrasion were measured using ASTM procedures with three replication. Finally, the specific weight was compared according to national building regulations. For data analysis, the SAS9.6 method was used. The validity and reliability of the test were calculated with 99% accuracy based on the test data and reported as an analysis of variance table using SAS software..

 The results of this research showed that the sample made from a combination of nanoclay, beech wood flour, glass fibers, and resin with 30% glass beads coating demonstrate increased impact resistance. The more glass beads were added to the coating, the higher the impact resistance of the composite. With a 30% coating using Caspian Sea rolling shell powder, the composite bending and tension strength increased compared to the control sample. The abrasion rate in composites prepared with 30% glass beads and 30% shell powder was lower after 200 cycles of abrasion compared to other samples. The thickness swelling rate after 48 hours of immersion in water was zero. Although the water absorption rate in the samples was very low, it can be said that samples with a higher amount of shell powder had higher water absorption compared to the control sample. The specific weight of the samples with the dimensions of the 20×30×0.7 cm3 was measured as 1211.9 kg/m³. The highest specific weight in the treatments was related to the sample treated with a 30% glass bead layer coded G180SH0 (p=1240 kg/m³), and the lowest specific weight was related to the untreated control sample coded G0SH0 (p=1192 kg/m³). Meanwhile, the lowest specific weight of stone used for building facades belongs to quartz (p=2000 kg/m³).

 In general, it can be mentioned that the composite prepared with a 30% glass bead coating has better quality in terms of abrasion, impact resistance, strength, and no water absorption compared to other samples. From the relative comparison of the specific weight of the samples, it can also be acknowledged that with an increase in specific weight, the impact and bending strength increases, as seen in the G180SH0 sample. Ultimately, the research objective of preparing a strong and lightweight composite for building facade applications was achieved.

One of the most serious challenges in the world and our country in cellulosic industries is raw material shortage. Therefore, the urgency to find out new alternatives with regard to forests area reduction and resulting lower wood harvesting is necessary. Lagerstroemia spp.‎ is a decorative bush that has many species and after pruning has a large amount of waste that can be used in the production of particle board, etc. The possibility of using this species requires morphological and chemical studies of Lagerstroemia spp. fibers.

This study was done according to ASTM and TAPPI standards. In this research, the biometric and chemical properties of the fibers in the longitudinal axis and at intervals of 5, 50 and 75% of the height of the stem after peeling have been done. Chemical characteristics including the percentage of cellulose, hemicellulose, lignin, extractive materials and ash, as well as anatomical parameters including fiber length, fiber diameter, cell cavity diameter and fiber wall thickness were measured and based on them, entanglement, runkle and The flexibility index was also calculated.

The results obtained for length, diameter, lumen diameter, and cell wall thickness of the Lagerstroemia spp fibers 0.66 mm, 16.64, 7.76 and 8.78 microns, respectively. The averages of slenderness, flexibility and runkel ratios were calculated as 40.1, 46.67, and 226.3, respectively. Also, holocellulose content 81.3%, alpha cellulose content 63.55%, cellulose content 53.15%, lignin content 21.28%, extractives soluble in acetone and water content, respectively 5.87% and 2.47% and ash content 1.54% was measured.

According to the results, Lagerstroemia spp. fibers in comparison with other species are a good raw material for manufacturing of cellulosic products.