In modern polymer composite technology, the use of waste products from other industries or processed waste is reasonable, but this requires more research. The purpose of the research presented in the article was to develop a methodology for selecting the composition of modified polyethylene foam and to assess the flammability of the materials obtained. In these studies, the content of recycled polyethylene, as a result of solving optimization problems, was taken to be equal to 23% of the mass of the polymer. CO₂ was used as the foaming gas. The structure of the polymer was modified with flame retardant. This made it possible to obtain materials belonging to the group of flammable, self-extinguishing materials, which significantly expanded the field of application of products based on polyethylene foam. Taking into account the possibilities of seamless insulation casings, the following systems of application of products based on polyethylene foam are considered: floors under mechanical load on the ground; permafrost soil insulation; insulation of external building elements in harsh climatic conditions; floating floors.

Wood fiber and its products are modified to increase fire and bio-resistance. The best results are achieved by using modifiers that enter into chemical interaction with the hydroxylated substrate, forming the organic matrix of the materials. The purpose of the research described in the article was to study the possibility of using boron-nitrogen compounds to modify cellulose and cellulose-containing materials to improve the performance, bio- and fire-protective properties of construction materials, as well as to optimize the consumption of boron-nitrogen compounds. As a result of the research, it was found that the boron-nitrogen compounds used in the compositions developed here chemically interact with hydroxyl groups at the C⁶-atom of cellulose. The chemical interaction of boron-nitrogen compounds with cellulose is an inter-crystalline process occurring without destruction of the crystal structure of the substrate since the modifier molecules bind with the more accessible hydroxyl groups of the amorphous regions of cellulose. Thus, surface modification with boron-nitrogen compounds does not result in accelerated aging of cellulose-containing materials and loss of strength but, on the contrary, increases the durability of wooden structures.

Сhemical interaction of cellulose with reactive groups of four-coordinate boron-nitrogen compounds is an intercrystalline process proceeding without destruction of cellulose crystalline structure; probably, the modifier molecules react with easier accessible hydroxyl groups of the amorphous cellulose regions. The formation of B-O-C ether bonds between OH groups of modifiers and more reactive hydroxyl groups of amorphous parts of cellulose results in redistribution of hydrogen bonds and, as a consequence, to rectification of cellulose macromolecules. Thus, when cellulose is treated with compositions based on four-coordinate boron-nitrogen compounds, crystalline structure of cellulose is not disrupted, hence this process can be called a "mild" modification. Such modification does not lead to accelerated aging of cellulose materials, rapid loss of strength and increases durability of wooden structures.

The possibility of using a nano-aluminum component in the cement composition has been considered. To ensure uniform distribution of the nano-aluminum component throughout the cement matrix, its suspension was stabilized using a sulfonaphthalene formaldehyde-based plasticizer and acoustic cavitation. It has been established that the nano-Al₂O₃ suspension is best stabilized when adding a plasticizer in an amount of 3-5 g/l and after an acoustic exposure at the optimal dispersion parameters: dispersion temperature–25±2 °C (the process is thermostated); dispersion time–20 minutes; and oscillation frequency-44 kHz. The study has shown that the compositions modified with a nano-aluminum component have improved strength and structural properties. On the first day of hardening, the compressive strength of the modified specimens increased by 20-24 % and at the grade age–by 31-35 % compared to the reference one. Introducing the stabilized nano-Al2O3 particles reduces the porosity for the first day of hardening by 12-13 % and at the grade age–by 27-29 %. It is recommended to add a nano-aluminum component as a stabilized suspension in an amount of 0.5-1.0 g/l to the cement composition.

The difficulty of wood protection from biocorrosion and fire is due to the fact that modifiers in use are washed out from the surface of the substrate under the influence of environmental factors. This results in a rapid loss of the protective effect and other practically important wood characteristics caused by the modification. To solve this problem is the aim of our work. Here, monoethanolaminoborate is used as a modifier, where electron-donating nitrogen atom provides a coordination number equal to four to a boron atom, which determines the hydrolytic stability of the compounds formed. Alpha-cellulose ground mechanically to a particle size of 1 mm at most was used as a model compound for the modification. X-ray photoelectron spectra were recorded on the XSAM-800 spectrometer (Kratos, UK). Prolonged extraction of the modified samples preceded the registration of the photoelectron spectra to exclude the fixation of the modifier molecules unreacted with cellulose. As a result of the experiment, boron and nitrogen atoms were found in the modified substrate, which indicated the hydrolytic stability of the bonds formed between the modifier molecules and the substrate. Therefore monoethanolaminoborate can be considered as a non-extractable modifier for wood-cellulose materials.

The actuality of this research is determined by the intensification of new ways of processing woody biomass. This requires revealing the impact of various physicochemical factors on the thermal degradation of wood biopolymers. Boron–nitrogen surface modifiers are used for wood antisepsis and we decided to check their effect on flammability. The aim of the research was to evaluate the flame retardant effect of boron–nitrogen surface modifiers of wood in an inert atmosphere (nitrogen was used). The evaluation was carried out by thermal analysis of modified and the control pine wood samples. The thermal analysis included thermogravimetry, differential scanning calorimetry and kinetic parameters of thermal degradation. It was found that the flame retardant effect of boron–nitrogen wood surface modifiers was not significantly pronounced in the nitrogen atmosphere. The mechanism of the flame retardant effect of boron–nitrogen compounds is reduced to “shielding” of the surface and increasing the proportion of carbonized residue. On the basis of correlation–regression analysis of kinetic parameters of wood thermodestruction in a nitrogen atmosphere, mathematical models of activation energy dependence on conversion were obtained and substantiated. The developed models can be further applied to calculate the predicted value of wood activation energy in the nitrogen atmosphere at any conversion value.