Abstract:

This review covers almost all known categories of compounds used to modify montmorillonite to obtain nanocomposites based on polar polymers. Organic modifiers such as quaternary ammonium ions, quaternary phosphonium ions, amino acids and other organic compounds are commonly used to modify montmorillonite (MMT). The main directions of scientific research in this field are considered, namely the modification of MMT with ammonium surfactants, phosphonium surfactants, amino acids and nonionic surfactants. The review used 67 sources related to peer-reviewed publications, mostly from the last 10-15 years. The largest number of publications devoted to the modification of MMT was published in the period from 2004 to 2016. Nanocomposites based on epoxy resins are especially widely presented in the literature. Epoxy-based materials have been used for many years as convenient matrices for dispersing MMT due to the advantages of properties of the obtained polymer nanocomposites, such as mechanical strength, non-flammability and thermal stability. The methods of surface modification of MMT with organic modifiers considered in the article are a powerful tool for the production of polymer nanocomposite materials based on polar polymers. Amine modification of MMT allowed the formation of highly effective materials, in particular epoxy/MMT materials. These nanocomposites have demonstrated extraordinary material properties compared to virgin polymers and can therefore be used as an alternative to conventional materials such as steel and wood, reducing the cost and weight of products. Nanocomposites based on polar polymers occupy an important place among all polymer nanocomposites as modern materials used in the aerospace, automotive and electrical industries.

Abstract:

The review article considers the current problem of environmental pollution with polymer waste. To solve one of the highest priority tasks, their recycling is considered, which is advisable from an economic, practical and scientific point of view. An assessment of the resources of secondary polymeric raw materials was made. The main ways of utilization of polymeric waste are given. The features of polymer waste recycling methods are determined. The issues of modification of polymer wastes are considered and the main methods of compatibilization of polymer mixtures are shown. Particular attention is paid to the methods and mechanisms of compatibilization of polymer composites based on recycled thermoplastics and crumb rubber from waste tires as a means of obtaining new composite polymer materials with valuable performance properties. The dependence of the properties of polymer composites on the filler concentration, particle size and shape, surface treatment methods, type and content, modifying additives and compatibilizers is shown. The creation of polymer composites based on secondary polymers and fillers of various nature contributes to the solution of social and economic problems of polymer waste.

Key words: polymer waste, secondary polyethylene, rubber crumb, compatibilization, polymer composites.

Abstract:

Thermoplastic film materials with a structure of pseudo-interpenetrating polymer networks (pseudo-IPNs) were created on the basis of natural semi-crystalline poly-3-hydroxybutyrate (PHB) and natural rubber (NR), the content of the NR was varied from 2 to 40 wt.%. Using the methods of Fourier Transform Infra-Red (FTIR) spectroscopy, scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), structure-properties relationships were studied for PHB/NR thermoplastic pseudo-IPNs at different ratios of the components. Significant non-additive increase in mechanical characteristics compared to the individual PHB was found for PHB/NR pseudo-IPNs samples with a low content (up to 15 wt.%) of NR. For the sample with a content of 5 wt.% NR, the greatest increase (~18.4%) in strength at break was fixed (σb ≈ 22.5 MPa); for a sample with a content of 10 wt.% NR, the largest increase (~ 215%) in elongation at break (εb ≈ 48.8%) was observed. By FTIR spectroscopy, it was found that certain changes in the crystal structure of the PHB matrix occurred in the samples of pseudo-IPNs at increasing the NR content; however, no changes in the chemical structure of the components were detected. The SEM method revealed spherical domains of the dispersed elastomeric NR phase distributed in the PHB matrix in the samples of PHB/NR pseudo-IPNs. These observations evidence the microphase separation of the system components due to their thermodynamic incompatibility. It is worth to note that the sizes of the domains of the dispersed elastomeric phase naturally increased from ~10–20 μm for pseudo-IPNs PHB/NR = 85/15 wt.%, up to ~ 100 μm for PHB/NR = 60/40 wt.%. Using TGA method, it is established that PHB/NR pseudo-IPNs samples are characterized by high resistance to thermo-oxidative destruction, which non-additively increases with increasing the NR content. Destruction of PHB/NR pseudo-IPNs samples occur in two main stages: at I stage (Td ~ 240–285 °С) the main weight loss of the samples is occurred due to the destruction of macromolecules of the PHB matrix; at II stage (Td ~ 320–380 °С) the oxidative destruction of NR component takes place. Calculations have shown that with increasing the NR content, the maximum rate of thermo-oxidative destruction of pseudo-IPNs samples decreases compared to the individual PHB by 5–52 % with increasing the NR content from 2 to 40 wt.%. Therefore, it means that their resistance to thermo-oxidative destruction increases. The results obtained by DSC method have shown that the introduction of NR and changes of the components ratio significantly and non-additively affect all the thermophysical characteristics of the samples studied. This indicates a significant restructuring of the microphase (amorphous and crystalline) structure of pseudo-IPNs synthesized due to the interpenetration of the components into the microphases of each other and the formation of mixed PHB/NR microphases with different ratios of the components.

Key words: poly-3-hydroxybutyrate, natural rubber, thermoplastic pseudo-interpenetrating polymer networks, microphase separation, degree of crystallinity.

Abstract:

In this work, the effect of ultrasonic dispersion time on the structural and thermophysical properties of nanocomposites was studied. Model systems were made based on polyethylene glycol and montmorillonite. All samples had the same composition and filler content (5% by weight), the ultrasonic treatment time was from 5 to 12 minutes. The methods of wide-angle X-ray scattering and differential scanning calorimetry were used to establish the dependence of the properties of the systems on the dispersion time. Data analysis of the obtained results showed that the variation of ultrasonic dispersion time significantly affects the properties of polymer nanocomposites. As the mixing time increases, the interplanar distance of montmorillonite increases, which indicates an increase in the degree of intercalation of the polymer matrix. At the same time, the crystallinity of the nanocomposite decreases, which corresponds to the increase in the area of the polymer/filler boundary layer. The melting temperature of the nanocomposite increases with increasing dispersion time. This trend is a consequence of the complication of the thermal movement of polymer molecules due to the presence of a developed surface of the filler. It is shown that with an increase in the sonication time, the part of the immobilized amorphous fraction of the polymer increases. This is explained by the fact that the polymer intercalated in the interlayer space of montmorillonite loses its ability to cooperative movement, that is, to glass transition. It was established that the maximum improvement of system properties is observed at a dispersion time of 10 min. In this state, the montmorillonite particles are most stratified, which leads to the maximum increase in the area of the boundary layer. During further mixing, processes of aggregation of montmorillonite particles and destruction of polymer molecules occur, which leads to the loss of the desired properties of the nanocomposite. Finding the optimal mixing time of a polymer nanocomposite makes it possible to obtain the desired properties of systems with a defined composition.

Key words: nanocomposites, montmorillonite, differential scanning calorimetry, ultrasonic dispersion, polyethylene glycol.

Abstract:

On the basis of the conducted literature review of biodegradable film-forming compositions using modified natural polymers, using the example of starch, it can be seen that the range of possibilities for its modification and the choice of suitable synthetic polymers depend on the method of production and the field of use, and are generaily aimed at protecting the environment. The physico-mechanical and structural characteristics of film-forming polymers polybutyrate PBAT and polycaprolactone PCL, which belong to biodegradable polymers processed by the extrusion method with the addition of thermoplastic starch, were studied. The destructive properties of film-forming compositions obtained from aqueous solutions of plasticized starch after UV irradiation for 90 days were studied. The maximum loss of strength reaches 86%, and the loss of elasticity is 93%.The structural changes of the compositions were investigated by the mass spectrometric method.

Key words: thermoplastic starch, plasticizing additives, film-forming polymer, destructive property.

By reacting a dian epoxy oligomer with guanidinium hydrochloride, a synthesis method of guanidinium-containing cationic proton oligomeric ionic liquids (OIL) capable of condensation reactions was developed. These compounds are characterized by an amphiphilic structure combining a flexible oligoether or hydroxyl-containing guanidinium oligoether block with terminal hydroxyl-containing guanidinium fragments. These compounds are capable of supramolecular organization due to the self-association of flexible oligoether blocks with terminal hydroxyl-containing guanidinium fragments from the outside of the formed cluster. They are characterized by two glass transition temperatures, which differ significantly in magnitude. The structure formed by the flexible oligoether component is determined by its segmental mobility with the glass transition temperature in the range (70–85 °C), and the terminal guanidinium fragments are responsible for the manifestation of the cohesive nature of the glass transition of the oligomer as a whole with the glass transition temperature in the range (-70)–(-60 °C), which characteristic of classical ionic liquids. The proton conductivity of the synthesized compounds in anhydrous conditions reaches a value of 1,94·10-3 S/cm at 120 °C and is determined not by the absolute value of the introduced protons, but by their specific number in relation to the MW oligomers. The synthesized OIL are of interest as electrolytes with an anhydrous conduction mechanism and starting reagents for the synthesis of ion-containing block copolymers of various functional purposes.

Key words: ionic liquids, oligomeric ionic liquids, guanidine, guanidinium ionic liquids, glass transition temperature, ionic conductivity.

Abstract:

The nanocomposites based on polyurethane matrix and multicomponent polymer matrices consisting of polyurethane and poly(hydroxypropyl methacrylate) with different contents of the last, and 1,2-propanediolisobutyl polyhedral oligomeric silsesquioxane (1,2-propanediolisobutyl-POSS), which was used as a functionalized nanofiller, were synthesized. The influence of the content of 1,2-propanediolisobutyl-POSS on intermolecular interactions and structural features of the nanocomposites was investigated by the method of IR-spectroscopy with Fourier transformation and attenuated total reflection (FTIR-ATR). The study of thermal curing of the model system, which consists of the adduct of trimethylolpropane with toluene diisocyanate and 1,2-propanediolisobutyl-POSS, made it possible to conclude that 1,2-propanediolisobutyl-POSS participates in the reaction of urethane formation using of one of the terminal hydroxyl groups, and it is incorporated into the polymer chain between cross-linking of  polyurethane networks. The investigation of multicomponent polymer matrices by FTIR-ATR spectroscopy was done and was shown that photopolymerization of second polymer poly(hydroxypropyl methacrylate) in the matrix of polyurethane was completed by the opening of a double bond and the formation of a linear polymer in the composition of semi-IPN. Studies of nanocomposites based on  multicomponent polymer matrices consisting of polyurethane and poly(hydroxypropyl methacrylate) with 15 and 30 % of the last by FTIR-ATR spectroscopy demonstrated the presence of POSS in the nanocomposites and the influence of POSS content on the structure of the studied systems and on the degree of phase separation. The POSS is “embedded” into the polymer chain between cross-linking of the polyurethane networks, with the additional formation of a complex system of intermolecular hydrogen bonds between the carboxyl and amine components of urethane groups in the nanocomposites.

Key words: nanocomposites, 1,2-propanediolisobutyl-POSS, polyurethane, poly(hydroxypropyl methacrylate), semi-interpenetrating polymer networks, FTIR-ATR spectroscopy.