Novel and durable flame-retardant modification based on the Schiff base and Pudovik reaction for wool fabric

Durable and formaldehyde-free flame-retardant (FR) modification of wool fabric using phosphorous compounds is of great interest. In this study, Schiff base imine groups were firstly introduced onto wool fiber through aldehyde-amine condensation between p-hydroxybenzaldehyde and wool fiber. Then, an efficient and durable FR wool fabric was fabricated by incorporating diethyl phosphite (DEP) into a Schiff base intermediate via the Pudovik reaction. The potential reaction mechanism among p-hydroxybenzaldehyde, DEP and wool fiber was explored. The thermal stability, smoke generation ability, FR ability and washing durability of the modified wool fabric were studied. The FR modification significantly increased the thermal resistance of wool fabric and suppressed smoke generation by half. The wool fabric modified by 20 g/L DEP was able to self-extinguish during the burning test, suggesting the higher FR efficiency of the DEP-incorporated Schiff base system. The modified wool fabric still self-extinguished after 20 commercial launderings, which is attributed to the covalent grafting of DEP onto wool fiber. Char residue analyses revealed the condensed charring FR mechanism of the DEP-incorporated Schiff base system on wool. This work provides a novel approach to prepare efficient and durable FR functional wool fabric via the Schiff base reaction and Pudovik reaction among p-hydroxybenzaldehyde, DEP and wool fiber.

Clays as Inhibitors of Polyurethane Foams’ Flammability

Polyurethanes are a very important group of polymers with an extensive range of applications in different branches of industry. In the form of foams, they are mainly used in bedding, furniture, building, construction, and automotive sectors. Due to human safety reasons, these applications require an appropriate level of flame retardance, often required by various law regulations. Nevertheless, without the proper modifications, polyurethane foams are easily ignitable, highly flammable, and generate an enormous amount of smoke during combustion. Therefore, proper modifications or additives should be introduced to reduce their flammability. Except for the most popular phosphorus-, halogen-, or nitrogen-containing flame retardants, promising results were noted for the application of clays. Due to their small particle size and flake-like shape, they induce a “labyrinth effect” inside the foam, resulting in the delay of decomposition onset, reduction of smoke generation, and inhibition of heat, gas, and mass transfer. Moreover, clays can be easily modified with different organic compounds or used along with conventional flame retardants. Such an approach may often result in the synergy effect, which provides the exceptional reduction of foams’ flammability. This paper summarizes the literature reports related to the applications of clays in the reduction of polyurethane foams’ flammability, either by their incorporation as a nanofiller or by preparation of coatings.

A new approach to calculating the time to the blocking of the escape routes due to the loss of visibility in the smoke of an indoor fire

Introduction. The accuracy of the visibility analysis in the event of an indoor fire strongly depends on the smoke-generating ability of substances and materials obtained experimentally in small-scale units. Therefore, the task is to develop a method of analysis that takes account of the scale factor and does not use the specific coefficient of smoke generation to identify the range of visibility in a full-scale room.Goals and objectives. The goal of the research project is a new approach to the calculation of the time to the blocking of the escape routes due to the loss of visibility with due regard for the scale factor and without regard for the specific coefficient of smoke generation. To achieve this goal, the analysis of fire development patterns in small-scale and full-scale rooms was carried out; theoretical dependences between the volumetric average optical smoke density and other volumetric average parameters of the indoor gas environment were obtained for these patterns, and calculation results, based on the obtained dependences, were compared with the experimental data.Methods. Methods, employed by the co-authors, included solving non-stationary equations based on the principle of conservation of indoor gas energy, optical density of smoke and oxygen mass for the cases of closed and open-type indoor heat and mass transfer. Fire tests were conducted in a small-scale facility. Theoretical and experimental data were compared.Results. Analytical dependences between the volumetric average optical density of smoke, a change in the volumetric average temperature, and the volumetric average partial oxygen density for closed and open indoor fire patterns were obtained. The series of fire tests involving the PVC insulated and sheathed bare (coverless) cable, exposed to the effect of the varying density incident heat flux, were carried out. Experimental dependences between the time, the optical density of smoke, and the specific coefficient of smoke generation were obtained. The obtained volumetric average optical density of smoke was compared with the experimental data using the proposed analytical expressions.Conclusions. The co-authors suggest using experimental dependences between the volumetric average optical density of smoke, changes in the volumetric average temperature or the volumetric average partial oxygen density obtained in a small-scale facility without solving the differential equation based on the principle of conservation of optical density of smoke.

Examination on the Effectiveness of an Image Processing Technology for the Visibility Enhancement of Firefighters in Fire

In the case of fire, it is important to enhance the visibility of firefighters for emergency activities (for example, fire extinguishment, rescue, and first-aid). In the present study, an image processing technology for visibility enhancement developed by the Korea Electrotechnology Research Institute was used to improve the visibility of firefighters. Image processing technology for visibility enhancement is a technology that combines Multi-Scale Retinex and smoke concentration equalization processing. To examine the effectiveness of the image processing technology in thick smoke conditions, the visibility was classified depending on the smoke generation in an enclosed compartment. In addition, comparative before and after evaluation of image processing technology was performed quantitatively. The visibility was divided into seven levels depending on the recognizable distance of each number plate. Thus, the visibility was improved from a maximum of four levels. Additionally, an in-depth interview was conducted with field crews who are the consumers of this technology; a view of more than 3.5 m was required to use this technology in fire fields.

Flammability properties of fire-retardant timber

Introduction. At present, the house-building industry, that produces timber structures, is in the process of sufficiently intensive development; however, high flammability of wood is the factor that restrains widespread use of timber in construction. The purpose of this work is to optimize the conditions of application of fire-retardant timber in the construction industry. The co-authors believe that the following problems are to be solved to attain this objective:● a comparative analysis of the fireproofing efficiency of several fire-proofing agents applied to different species of wood;● determination of the character of influence produced by fire proofing agents on fire retardant properties of wood.Methods of research. The fire proofing efficiency of sample compositions designated for wood was measured in compliance with the benchmark testing method specified in GOST R 53292 (p. 6.2). Experiments were launched pursuant to the methodology and with the help of measurement instruments specified in GOST 30244–94 (Method 2) to study the extent of the pine-tree timber flammability suppression. Critical values of thermal loads that may trigger inflammation and flame propagation in timber structures, that can be described using values of the critical surface density of the heat flow, were determined pursuant to GOST 30402–96 and GOST R 51032–97. The toxicity of combustion products and the smoke generation ability of fire-retardant pine-tree samples was assessed using standard methods and measurement instruments pursuant to GOST 12.1.044–89 (paragraphs 4.18 and 4.20).Research results and discussion. Biological flame retardants, integrated biological flame retardants that also ensure moisture protection, intumescent coatings, lacquers and varnishes that are ready for use and labelled as having group I and II fire-retardant efficiency pursuant to GOST R 53292, were studied in the course of this research project. The co-authors have identified that the mass loss by all fire-retardant compositions is below 9 %, if applied to samples of larch and oak-tree timber, same as if it were applied to standard samples of pine-tree timber.The findings of the experiment conducted to assess the flammability, ignitibility, flame propagation, smoke generation ability and toxicity of combustion products have proven the maximal efficiency of the composition designated for full-cell pressure impregnation of timber that ensures the properties of the material labelled as G1, V1, RP1, T2, D2.Conclusions. Hence, the research results have enabled the co-authors to assess the discrepancy between average mass loss values demonstrated by the samples of different species of timber (alder, linden, pine-tree, larch, and oak-tree).The comprehensive study of flammability properties of timber, treated by compositions that vary in their chemical composition and mode of action of the fire proofing agent, enabled the co-authors to identify the impact produced by versatile fire-proofing agents on different flammability properties of pine-tree timber with regard taken of the fire-safe use of construction materials and constructions of buildings and structures.

Nature of dust and smoke generation during gas-oxygen blasting in converter bath

The article presents the study of the nature of dust and smoke generation during gas-oxygen blasting of a converter bath. The main reasons causing metal waste have been determined. Influence of the process main parameters on metal loss has been studied during dust removal and evaporation of iron in the reaction zone. The authors have estimated the process of metal pulverization due to CO bubbles floating, determined by the rate of their rise to the bath surface. Specifics of temperature regime of the reaction zone and heat balance have been determined when adding fuel to the oxygen flow. Adding fuel to oxygen makes it possible to increase heat input into the bath, while reducing the rate of decarburization. This enables reduction of dust discharge during rupture and crush of metal films by gas bubbles. The effect of combustion products oxygen use on metal impurities oxidation is considered. By the example of blasting carbon and alloyed steel for mill rolls, it has been shown that the degrees of CO2 and H2O decomposition in the bath are the main qualities of gas-oxygen blasting. These indicators determine the oxidizing and heating properties of the blast. Assessment of change in total, consumed heat and its losses with exhaust gases, depending on degree of the oxygen flow dilution with natural gas (methane), has been carried out. Under these conditions, use of submersible combustion torches with change in their oxidizing ability makes it possible to solve various technological tasks, including provision of an effective way to reduce dust emission in converter process.

On the possibility of upgrading the composition of cable PVC compound

Upgrade of the composition of cable PVC-compound grade I40-13A with aluminum hydroxide has been carried out. Fire resistance, thermophysical and physical-mechanical properties of the obtained compounds have been investigated. It is shown that the modernization of the composition of cable PVC compound with aluminum hydroxide enables production of a fi re-resistant compound. It was found that aluminum hydroxide significantly changes the thermophysical properties of cable plastic compound. In particular, heat generation and smoke generation during plastic compound combustion are significantly reduced. It has been established that the physical-mechanical and rheological characteristics of the cable compound modernized with aluminum hydroxide remain at the level of the original compound. The optimal amount of aluminum hydroxide for the modernization of cable plastic compound of the I40-13A grade is 10–15 wt.%.

SOLVING THE PROBLEM OF CONTAMINATING SMOKED FOOD WITH CARCINOGENIC COMPOUNDS OF SMOKE

Meat and fish smoked products, widely produced nowadays, occupy a permanent place in the mass diet. The consumption of smoked meat is estimated by FAO at 15.6 million tons in 2019 (+40 % growth over the past ten years). This is due to the increased incomes of consumers in many countries, which made meat and fish smoked products, once classified as "premium" delicacies, more accessible to the majority. There has been a shortage of high-quality raw materials, which, combined with a highly competitive food market, forces manufacturers to reduce their costs by using non-traditional raw materials. The latter leads to increased use of processing raw materials with smoke to effectively mask individual defects in taste, appearance and consistency of products. As a result, there is a carcinogenic contamination problem because of polyaromatic hydrocarbons (PAHs) presented in the smoke and smoking liquids, and the growth of cancer. PAHs are formed as a result of pyrolysis of wood during smoke generation at temperatures above 450-480 °C. Currently used smoke generators and schemes for cleaning smoke from PAHs are not effective enough, so they do not eliminate the main cause of PAH formation, uncontrolled pyrolysis. The principal solution to the problem is to develop methods and equipment for producing smoke at temperatures below carcinogenic peaks. A successful solution is the method for producing smoke with an infrared power supply, implemented in the design of IR smoke generator (IRSG). The device allows to reliably maintain the pyrolysis temperature of wood below 450 °C. The effectiveness of the method and apparatus is confirmed by studies of products smoked with IR-SG, in which the content of Benzo(a)pyrene is less than 0.0002 mcg/kg, which is lower than the maximum permissible concentrations of this compound in food.