Search Results (15)

The industrial processing of innovative packaging papers with enhanced barrier properties has become ever more challenging due to the more stringent regulations on single-use plastics (SUPs), with an extended applicability to coated papers. Although the traditional packaging papers are based on renewable sources, they do not provide water and oil resistance and traditionally require the deposition of extruded polymer films or dispersion coatings that interfere with the paper recycling process. In this study, an alternative method has been investigated through the impregnation of papers with various types of biowax, including a synthetic PE wax, palm oil wax, sunflower wax, rice bran wax, rapeseed wax, castor wax, rice bran wax, and candelilla wax. The close control of processing conditions in an industrial pilot-line is critical to produce an optimized product quality with enhanced water and oil contact angles. In particular, the variations in wax type and wax loadings after single- or dual-side impregnation and the control of processing temperatures have been related to the oil and water contact angles. The stable water contact angles in the range of 100 to 120° were obtained depending on the biowax type. Meanwhile, the increase in oil contact angles up to 60° is in line with the enhanced grease resistance. The good recyclability scores of biowax-impregnated papers were demonstrated following the “Harmonized European laboratory test method to generate parameters enabling the assessment of the recyclability of paper and board products in recycling mills with conventional process (Part I)”, version February 2024. Full article

Calcined and acid-leached kaolin impregnated with Fe(NO₃)₃·9H₂O (6.6 wt. % Fe₂O₃) was developed as an inexpensive bifunctional catalyst for the slow fixed-bed pyrolysis of polypropylene (PP) and low-density polyethylene (LDPE). Experiments were run with catalyst-to-plastic mass ratios of 1:4, 1:2, and 1:1 in a quartz tube reactor heated from 25 to 800 °C. For PP, increasing the Fe/kaolin loading progressively raised non-condensable gas from 26 wt. % to 44 wt. % and drove liquid aromatics from 27.9% to 72.3%, while combined paraffins olefins fell to 2.5% and wax exhibited a 46 → 24 → 36 wt. % trend. In contrast, LDPE at a 1:4 ratio already yielded 56 wt. % oil and only 22 wt. % wax; further catalyst addition mainly enhanced CH₄/CO-rich pyrolysis gas (PyGas) and char without substantially boosting aromatics. Gas analysis confirmed that Fe₂O₃ reduction and kaolin de-hydroxylation generated in situ H₂O, CO, and H₂. Given the catalyst’s low cost, regenerability, and ability to valorize the two most abundant waste polyolefins within the same reactor, the process offers a scalable route to flexible fuel and gas production from mixed plastic streams. Full article

In this paper, a combined modification method using thermal modification and wax impregnation was investigated. The advantage of this method is that the two modification steps are completed in one step. Two different wood species, beech (Fagus sylvatica) and Scots pine (Pinus sylvestris), were investigated. The effects of the treatments were tested regarding the wax uptake, mass loss, density, equilibrium moisture content, swelling, water contact angle, strength properties, and durability. Through the synergistic effect of the combined modification, it was possible to significantly improve the dimensional stability and decrease the hygroscopicity and equilibrium moisture content, while swelling anisotropy was not affected. It was proven that the wax uptake during this method is highly dependent on the treatment temperature, resulting in a large density increase. The treatment resulted in an obvious color change as well. Bending strength was not affected by the combined treatment, while impact bending, compression strength, and Brinell hardness were improved. High durability was observed after the combined modification method, indicating that lower treatment temperatures are enough to efficiently protect the wood. Full article

In this research, the effect of the addition of coconut fibers coated with hydrophobic substances as reinforcement material in mortars was evaluated. Fibers of different sizes (1, 2, and 5 cm) were pretreated with linseed oil and paraffin wax, in order to obtain a mortar/fiber ratio of 0.5% and 1% by weight. The chemical resistance of the fibers were evaluated before and after being exposed to a concentrated solution of Ca(OH)₂ in order to simulate the alkaline environment of the cement. The physicochemical characterization of the fibers was conducted by DTG (derivative thermogravimetry), TGA (thermogravimetric analysis), and FTIR (Fourier transform infrared spectrometry). The mechanical strength of the fiber-reinforced mortars was evaluated by compression and flexural tests. The effect of fiber degradation on mechanical behavior was evaluated between 28 days of processing. The results showed that the highest compressive and flexural strength were obtained with the composites reinforced with coconut fiber of 0.5% by weight, length of 1 cm, and paraffin wax as the impregnation substance. Full article

Green surfactants have significant potential for improving environmental remediation methods. The aim of the present study was to formulate a green natural detergent containing the biosurfactant produced by Starmerella bombicola ATCC 22214 grown in 1.2% canola oil, 10% sucrose, and 0.5% corn steep liquor. The biosurfactant reduced surface tension to 31.84 mN/m and was produced at a yield of 22 g/L. Twelve formulations were proposed using cottonseed oil as the natural solvent and different stabilisers (vegetable wax, hydroxyethyl cellulose, and sodium alginate). The detergent was evaluated for its emulsifying capacity and stability over a 10-day period. Ecotoxicity was investigated using the marine recruitment test on metal plates covered with paint into which the biosurfactant was incorporated as well as tests with a microcrustacean and vegetable seeds. The formulation designated H, consisting of 1% biosurfactant, 40% cottonseed oil, and 2% hydroxyethyl cellulose, achieved the best results. The formulation exhibited both stability and emulsifying capacity (100% of petroleum). The ecotoxicity tests revealed the safety of the natural detergent. The detergent achieved satisfactory oil dispersion and solubilised 98% of the oil impregnated on the rock. The results indicate that the natural detergent holds promise for efficiently cleaning up environmental areas contaminated with oil and petroleum products. Full article

In this paper, the electrochemical non-enzymatic detection of Riboflavin (RF) was proposed based on its catalytic reduction in a Thionine-coated Cadmium Selenide Quantum dots (TH@CdSe QDs)-modified paraffin wax-impregnated graphite electrode (PIGE) that was prepared using a novel approach. The synthesized TH@CdSe QDs were confirmed by UV-Vis spectroscopy, Confocal Raman Microscopy and High Resolution Transmission Electron Microscopy (HRTEM) studies. The electrochemical response of the TH@CdSe QDs-modified PIGE was studied by cyclic voltammetry. The voltammetric response of RF at the TH@CdSe QDs-modified PIGE showed higher current than the bare PIGE. Under optimum conditions, the electrocatalytic reduction currents of RF was found to be linearly related to its concentration over the range of 1.6 × 10⁻⁷ M to 1.4 × 10⁻⁴ M with a detection limit of 53 × 10⁻⁹ M (S/N = 3). The TH@CdSe QDs-modified PIGE was utilized as an amperometric sensor for the detection of RF in flow systems was performed by carrying out hydrodynamic and chronoamperometric experiments. The TH@CdSe QDs-modified PIGE showed very good stability and a longer shelf life. The applicability of the fabricated electrode was justified by the quantification of RF in commercial tablets. Full article

Supercritical carbon dioxide (scCO₂) is extensively used for extracting chemicals from materials, but the impregnation of materials with chemicals using scCO₂ has received little attention in comparison. To the best of our knowledge, most technologies described in the literature operate by the principle of diffusion, where impregnation yield is limited by solubility. The objective of this exploratory study is to prove the feasibility of an scCO₂ impregnation process that can extract solutes from one material and release them into another material through a single extraction/impregnation stage that can be applied in cycles to increase the yield. The feasibility of the concept was proven in the laboratory using radiata pine bark wax as the solute and radiata pine wood as the impregnated material. Extraction/impregnation tests were performed at temperatures between 40 and 60 °C, pressures between 12 and 16 MPa, and with the addition of ethanol and acetone as co-solvents. The study demonstrated the feasibility of multi-cycle scCO₂ impregnation of wax into wood, where the novelty of the concept is the implementation as traditional pressure impregnation methods. Full article

Based on the reduction of environmental pollution, a biological enzyme assisted alkali-oxygen pulping method was explored to improve the delignification efficiency and fiber accessibility of wheat straw and improve the properties of wheat straw pulp. In this paper, lipase and xylanase were used to pretreat wheat straw and the effects of different enzyme types and enzyme dosage on the microstructure and pulp properties of wheat straw were investigated and experimented. The results showed that the lipase can remove fat and wax on the surface of wheat straw, while xylanase degraded the hemicellulose components, such as xylan, of wheat straw fiber, destroyed the structure of the lignin-carbohydrate complex, increasing lignin removal as a result and enhancing the impregnating, diffusion and penetration of alkali. Compared with wheat straw without enzyme pretreatment, the skeleton of wheat straw pretreated by enzyme became looser, the internal cavity appeared and the wall cavity became thin and transparent. The fines decreased obviously and the length of fibers increased. After combined pretreatment with lipase (15 U·g⁻¹) and xylanase (15 U·g⁻¹), the pulping performance of wheat straw was improved and the tensile index (97.37 N·m·g⁻¹), brightness (40.9% ISO) and yield (58.10%) of the pulp increased by 12.9%, 19.9% and 9.9%, respectively. It can be seen that enzyme pretreatment is a green and effective approach to improving the alkali-oxygen pulping performance of wheat straw. Full article

The outermost surface of wheat straw (WS) is covered with hydrophobic lipophilic extracts and silica, which affects follow-up processes such as impregnation pretreatment of pulping and papermaking. In this study, a strain named Bacillus licheniformis (B. licheniformis) was screened from the black liquor of papermaking, which was used to explore the effect of its treatment on the waxy cuticle of WS. Scanning electron microscope-energy dispersive spectroscopy (SEM-EDS) showed that the B. licheniformis had a certain destructive effect on the outer surface of WS and the content of Si on the outer surface decreased by 80%. The results of FTIR and X-ray photoelectron spectroscopy (XPS) displayed that the wax composition on the outer surface of WS decreased and the fiber structure inside appeared. The mechanical properties of paper demonstrated that the treated WS is still feasible in this field and the content of Si in the black liquor is reduced by 33%. Therefore, the WS treated by B. licheniformis can destroy the waxy cuticle on its outer surface and improve the wettability of WS. It provides a new idea to alleviate the “Si interference” problem of alkali recovery in WS traditional pulping and papermaking. Full article

The sudden availability of Italian stone pine (Pinus pinea L.) wood due to the infestation of pathogenic fungi and insects highlighted the need to promote its use as a short supply chain resource in Italy and other Mediterranean countries. However, the durability of stone pine sapwood must be enhanced if outdoor use is to be considered. The impregnability of stone pine wood was studied following the standard EN 351-1:2008, using immersion, vacuum, and high-pressure methods with natural waxes and organic solvent-based and copper-amino-based preservative solutions. The efficacy of the impregnation was determined by calculating the kilos of preservative absorbed per cubic meter of wood and by measuring the penetration depth of the preservative. Thermal modifications were carried out using five different maximum temperatures, and their efficacy was determined by measuring the mass loss and color change. Subsequent to thermal treatments, the wood was exposed to a water-vapor-saturated atmosphere, and the increase in mass was calculated for different periods. Stone pine and Scots pine sapwoods showed similar response to the treatments with the exception of soaking impregnation methods where stone pine showed higher uptake, in particular when Silvanolin was used. Our investigation shows that stone pine can be a suitable short supply chain resource in Italy that, when impregnated, could be tested for outdoor use, exactly as is the case with Scots pine. Full article

To address the drawback of low thermal conductivity of conventional organic phase change materials (PCMs), a paraffin-wax-based phase change composite (PCC) was assembled via a vacuum impregnation method, using a new type of carbon fiber network material as the supporting matrix. The carbon fiber sheet (CFS) material exhibited a network structure comprising high-thermal-conductivity carbon fibers, beneficial for enhancing the heat transfer properties of the PCC. The sheet-shaped carbon fiber material was stacked and compressed, and then impregnated with the liquid paraffin wax PCM to form the composite. The thermal conductivity, durability, shape stability, chemical stability, and heat storage characteristics of the PCC specimen were carefully analyzed. The maximum thermal conductivity of the PCC was 11.68 W·m⁻¹·K⁻¹ (4670% compared to that of pure paraffin) in the radial direction, and 0.93 W·m⁻¹·K⁻¹ in the axial direction of the sample, with 17.44 vol % of added CFS. The thermal conductivity retention rate after 200 thermal cycles was 78.6%. The PCC also displayed good stability in terms of chemical structure, shape, and heat storage ability. This study offers insights and a possible strategy for the development of anisotropic high-thermal-conductivity PCCs for potential applications in latent heat storage systems. Full article

Thermal modification (TM) improves the hydrophobicity, dimensional stability, and durability of wood, but TM commonly results in severe color change and mechanical strength loss as wood is treated at higher temperature. In this study, Pterocarpus macrocarpus Kurz wood was thermally modified at moderate temperature (150 °C) and higher temperature (200 °C), and subsequently TM wood at 150 °C was subjected to wax impregnation (WI), the effect of a combination of TM and WI on the hygroscopicity, dimensional stability, and mechanical properties, as well as the micro-structure of wood, were investigated and compared. The results showed that the mass loss of wood was slight at 150 °C TM, while it became severe at 200 °C TM conditions. TM conditions affected the amount of the subsequent wax impregnation; the equilibrium moisture content (EMC), water absorption ratio, and adsorption and absorption swelling of the 150 °C TM + WI group were lower than that of 200 °C TM, and presented the lowest value. Moderate temperature TM could improve the hydrophobicity and dimensional stability of wood, but WI played a key role in the improvement. TM decreased the modulus of rupture (MOR) of wood, while WI improved the MOR. TM increased the modulus of elasticity (MOE) of wood, but WI had little effect on MOE; Scanning electron microscope (SEM) observation showed that the wax was successfully impregnated into the wood interior, and presented an even distribution on the internal surfaces of wood cells; Fourier-transform infrared spectroscopy (FTIR) spectra verified the changes of –OH and C=O after TM and TM + WI, which contributed to decreasing hygroscopicity and improving the dimensional stability of the wood. Impregnated wax improved wood mechanical strength, but decreased the lightness, and deepened the color of wood. The combination of thermal modification at moderate temperature with subsequent wax impregnation is a practical approach for improving wood properties. Full article

Wood is an environmentally friendly material, but some natural properties limit its wide application. To study the effect of a combination of heat treatment (HT) and wax impregnation (WI) on wood hygroscopicity, dimensional stability, and mechanical properties, samples of Pterocarpus macrocarpus Kurz wood were subjected to HT at a moderate temperature of 120 °C and a high temperature of 180 °C, for a 4 h duration. Subsequently, half of the 120 °C HT samples were treated with WI at 90 °C. The results showed that 180 °C HT and WI decreased the capacity of adsorption and liquid water uptake and swelled the wood significantly, while WI had the biggest reduction. The effect of 120 °C HT was significant only on decreasing the capacity of adsorption and the swelling of liquid water uptake. The bending strength (MOR) of wood decreased only after 180 °C HT, and 120 °C/4h HT and WI had no significant influence on MOR. The bending stiffness (MOE) increased significantly after 180 °C HT and WI, while 120 °C/4h HT had no significant influence on MOE. Therefore, the combination of moderate-temperature HT can act synergistically in the improvement of certain aspects of wood properties such as capacity of water adsorption and liquid water uptake. WI effectively improved wood hygroscopicity, dimensional stability, and mechanical properties. Full article

Wax impregnation is an effective approach to improve wood water resistance. However, melted waxes require special equipment and cannot penetrate deep enough into wood. Recently, wax emulsions show excellent efficiency in wood modification. In this study, paraffin Pickering emulsion stabilized by low dispersed SiO₂ nanospheres was used to impregnate poplar wood. The microstructure and storage stability of the emulsion were evaluated. The dimensional stability, water uptake, wettability, and thermal stability of treated wood were also investigated. After homogenization, a milk-white oil-in-water (O/W) paraffin Pickering emulsion stabilized by the nano-SiO₂ (diameter of ~76 nm) was formed and demonstrated excellent storage stability. Paraffin Pickering emulsion could penetrate into the wood structure. The emulsion-treated wood was endowed with a moderate anti-swelling efficiency (ASE), high water resistance, and low wettability. Moreover, the addition of nano-SiO₂ could improve the thermal stability of the treated wood. Full article

Natural wood is susceptible to moisture during its practical use, limiting not only service life but also the range of uses. In this study, plant extracts, specifically linseed oil and carnauba wax (both environmentally friendly and water-repellent substances), were examined as a means to mitigate limitations of natural wood. Stable and homogenous epoxidized linseed oil/carnauba wax emulsions with an average particle size less than 230 nm were used as a modifier to enhance the performance of wood. Weight percentage gain, bulking coefficient, micromorphology, chemical structure, moisture adsorption, contact angle, water repellency, and dimensional stability of treated wood were measured. Using a scanning electron microscope (SEM), it was observed that carnauba wax and epoxidized linseed oil acted as a mechanical barrier and could partially cover or block vessels, pits, and wood rays. Furthermore, the hydrophobicity of wood increased significantly after emulsion impregnation. However, there was no obvious chemical reaction between epoxidized linseed oil and the main components of wood in the Fourier transform infrared spectroscopy (FTIR) results. The combined effect of epoxidized linseed oil and carnauba wax was apparent in both decreased water absorption and dimensional deformation. Poplar wood impregnated with an epoxidized linseed oil/carnauba wax complex emulsion shows potential for improving water-related properties. Thus, the complex emulsion modification can improve the inherent shortcoming of poplar wood effectively. Full article