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This paper aims to evaluate the effect of multiple additions of sodium hydroxide (NaOH) on the properties of bark‐phenol‐formaldehyde (BPF) adhesives, and to lay the foundations for further studies on bark utilisation.

Synthetic technologies that used multiple additions of NaOH were developed for the production of BPF adhesives. Differential scanning calorimetry (DSC), gel permeation chromatography (GPC) and plywood bond were used to evaluate properties of the PF and BPF adhesives.

The number of NaOH additions had an important effect on many BPF adhesive properties, such as gel time, free formaldehyde content in adhesive, thermosetting peak temperature, molecular weight distribution, as well as the wet shear strength and free formaldehyde release of the bonded plywood panels. The study determined that a two‐step process for adding NaOH offers a prospective synthetic technology for BPF adhesive production. This technology made it possible to use 28.6 per cent bark by weight and resulted in plywood with properties comparable with those of plywood bonded with a commercial PF adhesive. However, BPF adhesives prepared with more than two NaOH additions were fast‐curing.

BPF adhesives are very complex systems with many unknown variables, such as the chemical structures of bark derivatives from phenolation and adhesive synthesis. To further improve the curing rate and adhesion of BPF, future investigations should be based on a two‐addition process or attempt to increase the amount of NaOH in the second addition.

The BPF adhesive prepared with two NaOH additions and 28.6 per cent bark was comparable with a commercial PF adhesive in terms of adhesive properties and plywood bond quality. These results indicate that this technology shows potential for commercial applications.

Synthetic technologies using multiple additions of NaOH were developed to produce BPF adhesives. The BPF with two additions of NaOH seemed to be comparable with a commercial PF adhesive.

The purpose of this paper is to evaluate the effect of different amounts of sodium hydroxide (NaOH) introduced during the resin synthesis on the properties of bark‐phenol‐formaldehyde (BPF) adhesives aims at achieving a balance between storage life and other properties of BPF adhesives.

Based on the best synthetic technologies for the production of BPF adhesives obtained in a previous study, a new synthetic technology is developed for the production of BPF adhesives that involve a three‐step addition of NaOH using different amounts of NaOH in the third charge. Gel permeation chromatography is used to evaluate properties of the phenol‐formaldehyde (PF) and BPF adhesives.

The amount of NaOH in the third charge has an important influence on many BPF adhesive properties. The paper determines that the synthetic technology involving three‐step NaOH additions with only water introduced in the third charge of NaOH produces a BPF adhesive with the longest storage life and best bonding strength.

BPF adhesives are very complex systems with many unknown variables.

The improved storage life of the BPF adhesive prepared with the new synthetic technology is comparable to that of a commercial PF adhesive, which indicates that this new technology shows greater potential for commercial applications.

A new synthetic technology is developed to produce a BPF adhesive that is more comparable to commercial PF adhesives than other BPF adhesives in terms of storage life and other resin properties.

Disappearing ink was prepared using different concentrations of thymolphthalein, phenolphthalein and their mixture, applying to different types of handwriting surfaces such as cotton, polyester and polyamide. The effects of thymolphthalein, phenolphthalein and alkali concentrations (i.e. pH) on the fading time were studied. The handwriting stability increased when the concentration of thymolphthalein or phenolphthalein was increased. At a high concentration of alkali with phenolphthalein and its mixture with thymolphthalein, the handwriting stability decreased with polyester or polyamide handwriting surfaces and the stability increased in the case of cotton. When the faded handwriting surfaces were subject to the thermal effect in a thermostatically controlled oven at 100°C for 10 minutes by hanging them with suitable hooks, there was no change in the faded handwriting. When they were at 150°C for 20 minutes, the faded phenolphthalein ink, which contained 0.5ml of 1N NaOH, was visible and shown red on the polyester and polyamide handwriting surfaces, but there was no change on the faded cotton handwriting surface.

The purpose of this paper is to study to minimize the self‐corrosion rate of Type 57S aluminium containing (97.7 per cent Al, 2 per cent Mn and 0.03 per cent Mg) in 2 M NaOH solution containing 0.2 M zinc oxide and 700 ppm of polyaniline.

The approach is used to measure weight loss and polarization measurements.

Results obtained show that as the amount of polyaniline is increased, the self‐corrosion rate of Alloy 57S aluminium decreases appreciably. Additionally, the open circuit potential is more in the case of 700 ppm level of polyaniline (−1.630 V) compare to 600 ppm level of polyaniline (−1.587 V). From this paper, it is also observed that the anodic polarization is greater than the cathodic polarization, thereby indicating that the overall corrosion of Alloy 57S 2 M NaOH containing 0.2 M ZnO and 700 ppm of polyaniline is under anodic control.

The results of the study clearly reveal that the overall corrosion of Alloy 57S aluminium in 2 M NaOH containing 0.2 M ZnO and 700 ppm of polyaniline is under anodic control. Hence, the 57S grade aluminium can be used as a potential candidate (anode) in alkaline batteries.

The purpose of this study is to investigate the effect of various heat conditions on the durability of eggshell powder (ESP)–flyash (FA) geopolymer subjected to wetting–drying cycles.

In this study, two waste materials, ESP and FA, which are destined for landfills, were used as precursors to produce geopolymers in a sustainable manner. The mixture of Na₂SiO₃ and NaOH was used as a liquid alkaline activator in geopolymerization. The ESP and FA content were varied as 30, 50 and 70% and Na₂SiO₃/NaOH ratios were varied as 0.5, 1 and 2. Geopolymer samples were cured at three heat conditions: 25°C (ambient temperature), 50°C and 80°C for seven days prior to durability tests.

The results of this study revealed that the strength loss of the geopolymer decreases with an increase in curing temperature up to 50°C and then increases for higher temperature up to 80°C. Further, the strength loss of the geopolymer decreases with an increase in FA replacement and Na₂SiO₃/NaOH ratio. Geopolymer composites exhibited early strength development because of the inclusion of calcium-rich ESP. The weight loss of the ESP–FA geopolymer follows a similar pattern of strength loss. Geopolymer samples previously cured at optimum heat condition of 50°C for seven days exhibited higher durability.

The inclusion of calcium-rich ESP in FA-based geopolymer is novel research. As ESP–FA geopolymer composites show higher mechanical strength and higher durability compared to Indian standards, the potential use of this geopolymer can be in road subbases/subgrades.

Bacterial cellulose (BC) is an ideal alternative filtering material. However, current functionalization approaches for BC have not been fully discovered industrially as well as academically applying textile processing. This study aims to create a sustainable fabric-like membrane made of BC/activated carbon (AC) for applications in filtration using textile padding method, to protect people from respiratory pandemics.

Fabric-like BC is first mechanically dehydrated then AC is loaded via a textile padding step. The finishing efficacy, properties of fabric-like BC/AC and NaOH pretreatment are analyzed and characterized by scanning electron microscope (SEM), field emission scanning electron microscope (FE SEM), X-ray diffraction (XRD), CIELab color space, color strength (K/S), nitrogen adsorption-desorption isotherm including Brunauer–Emmett–Teller (BET) specific surface area and Barrett–Joyner–Halenda (BJH) pore size and volume.

This research results in a fabric-like BC/AC with pore diameters of 3.407 ± 0.310 nm, specific surface area of 115.28 m²/g and an efficient scalable padding process, which uses 8 times less amount of chemical and nearly 30 times shorter treating duration than conventional methods.

Our globe is now consuming an alarming amount of non-degradable disposable masks resulting in massive trash buildup as a future environmental problem. Besides, current disposable masks requiring a significant upfront technological investment have posed challenges in human protection from respiratory diseases, especially for countries with limited conditions. By combining a sustainable material (BC) with popular padding method of textile industry, the fabric-like BC/AC will offer sustainable and practical values for both humankind and nature.

This research has offered an effective padding process to functionalize BC, and a unique fabric-like BC/AC membrane for filtration applications.

This study aims to study the simultaneous treatment of polyethylene terephthalate (PET) fabric with sodium hydroxide (NaOH) and TiO₂ nanoparticles (NPs).

PET fabrics loaded by TiO₂ NPs were investigated by the use of scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and Fourier transformed infrared spectroscopy (FT-IR). Factors affecting the finishing process such as NaOH and TiO₂ NPs concentrations, finishing duration and temperature were discussed.

The finished PET fabrics imparted new properties such as antimicrobial and ultraviolet protection factor protection, what is undoubtedly will increase the spread of this type of fabric and its use in new areas.

The method used mainly depends on activating the surface of PET fabrics by a chemical method, specifically NaOH to cause partial decomposition, which may lead to an environmental impact.

The obtained results revealed that the simultaneous treatment of PET fabric with NaOH and TiO₂ NPs showed antimicrobial and UV protection properties. They exhibited a strong antimicrobial activity and UV protection efficiency even after five washing cycles, indicating excellent laundering durability.

The approach has simplicity and implementability on an industrial scale without cost investment.

To investigate the inhibiting effect of the cationic surfactant cetyl trimethylammonium chloride (CTAC) on aluminum (Al).

Pure aluminum rods were immersed in hydrochloric acid (HCl) and sodium hydroxide (NaOH) solutions for weight‐loss tests and potentiostatic polarization measurements.

The inhibition action depends on the concentration of the inhibitor, the concentration of the corrosive media, and the temperature. The inhibition efficiency in NaOH was higher than that in HCl solutions. In both acidic and basic media, the increase in temperature resulted in a decrease of the inhibition efficiency and a decrease in the degree of surface coverage. The results were indicative of increased aluminum dissolution with increasing temperature. It was found that adsorption of CTAC on the aluminum surface follows Temkin's isotherm in HCl and Langmuir's isotherm in NaOH.

Clarifies the effects of concentration and temperature on the inhibition efficiency of a cationic surfactant on aluminum.

Concrete is a building material widely used for the infrastructural development. Cement is the binding material used for the development of concrete. It is the primary cause of CO₂ emission globally. The purpose of this study is to develop sustainable concrete material to satisfy the present need of construction sector. Geopolymer concrete (GPC) is a sustainable concrete developed without the use of cement. Therefore, investigations are being conducted to replace the cement by 100% with high calcium fly ash (FA) as binding material.

High calcium FA is used as cementitious binder, sodium hydroxide (NaOH) and sodium silicates (Na₂SiO₃) are used as alkaline liquids for developing the GPC. Mix proportions with different NaOH molarities of 4, 6, 8 and 10 M are considered to attain the appropriate mix. The method of curing adopted is ambient and oven curing. Workability, compressive strength and microstructure characteristics of GPC are analysed and presented.

An increase of NaOH in the mix decreases the workability. Compressive strength of 29 MPa is obtained for Mix-I with 8 M under ambient curing. A polynomial relationship is obtained to predict the compressive strength of GPC. Scanning electron microscope analysis is used to confirm the geo-polymerisation process in the microstructure of concrete.

This research work focuses on finding some alternative cementitious material for concrete that can replace ordinary portland cement (OPC) to overcome the CO₂ emission owing to the utilisation of cement in the construction industry. An attempt has been made to use the waste material (high calcium FA) from thermal power plant for the production of GPC. GPC concrete is the novel building material and alternative to conventional concrete. It is the ecofriendly product contributing towards the improvement of the circular economy in the construction industry. There are several factors that affect the property of GPC such as type of binder material, molarity of activator solution and curing condition. The novelty of this work lies in the approach of using locally available high calcium FA along with manufactured sand for the development of GPC. As this approach is rarely investigated, to prove the attainment of compressive strength of GPC with high calcium FA, an attempt has been made during the present investigation. Other influencing parameter which affects the strength gain has also been analysed in this paper.

To explore the effect of acrylic acid polymerization and NaOH treatment of nylon‐6 on hemoglobin washability.

The nylon‐6 was chemically grafted with acrylic acid and treated with NaOH for the purpose to improve the washability of hemoglobin as a blood protein soil. The structural change before and after graft polymerization was analyzed by X‐ray photoelectron spectroscopy and scanning electron microscopy. The moisture regain, the contact angle, and the washability were each measured.

Graft polymerization and NaOH treatment of nylon‐6 changed the surface energy and structure of nylon‐6 causing the washability of hemoglobin to improve. Compared to ungrafted nylon‐6, the hydrophilic properties were increased remarkable by graft polymerization and NaOH treatment, which reulted in the improvement of washability.

Hemoglobin is one of the most difficult soils to remove from the fabric. The paper might be of interest to those who would consider purchasing fabrics that are good at both hydrophilic properties and washability.

The study on washability of hemoglobin as a blood protein soil for grafted fabric has not been reported so far. The results of this research may be used in a basic research for the development of new process which is capable of improving of hemoglobin washability.