Wood characterized by desired mechanical properties and wood joining material is essential for creating wooden structures. The polymer adhesives are suitable for such applications due to the possibility of energy dissipation from stresses generated by wooden structures and the elimination of thermal bridging, which are common problems in metal joining materials. This research focuses on the thermophysical properties of the laboratory-prepared flexible and rigid polyurethanes to select an appropriate polymer adhesive. Our results showed that the highest thermal stability was in the case of the new PSTF-S adhesive, which reached 230 °C, but the lowest mass loss in the air environment was around 54% for the PS material. The mean thermal expansion coefficient for F&R PU adhesives was 124–164∙10−6 K−1. The thermal diffusivity of examined adhesives varied between 0.100 and 0.180 mm2s−1. The thermal conductivity, depending on the type of polyurethane, was in the 0.13–0.29 W∙m−1∙K−1 range. The relative decrease in thermal diffusivity after heating the adhesives to 150 °C was from 2% for materials with the lowest diffusivity to 23% for the PU with the highest value of heat transfer. It was found that such data can be used to simulate wooden construction joints in future research.
Glasses and devitrificates from the SiO2–B2O3–P2O5–K2O–CaO–MgO system with constant contents of SiO2 and P2O5 network formers, modified by the addition of B2O3, were analyzed. All materials were synthesized by the traditional melt-quenching technique. The glass stability (GS) parameters (Krg, ∆T, KW, KH) were determined. The effect of the addition of B2O3 on the GS, liquation phenomenon, crystallization process, and the type of crystallizing phases were examined using SEM-EDS, DSC, XRD, and Raman spectroscopy imaging methods. It was observed that the addition of B2O3 increased the tendency of the glass to crystallize. Both phosphates (e.g., Ca9MgK(PO4)7, Mg3Ca3(PO4)4), and silicates (e.g., K2Mg5(Si12O30), CaMg(Si2O6), MgSiO3) crystallized in the studied system. The Raman spectrum for the orthophosphate Mg3Ca3(PO4)4 stanfieldite type was obtained. Boron ions were introduced into the structures of crystalline compounds at high crystallization temperatures. The type of crystallizing phases was found to be related to the phenomenon of liquation, and the order of their occurrence was dependent on the Gibbs free enthalpy.
1 August 2022 in Journal of Thermal Analysis and Calorimetry
The present study provides a deep insight into the implications of sulphate addition on glass forming properties of materials from the SiO2–P2O5–K2O–MgO/CaO/MgOCaO systems, by combining: preliminary investigation of as-synthesized materials (XRD, XRF, SEM–EDS), detailed characteristics of their thermal behaviour (DSC), estimation of various glass-stability parameters, in-depth analysis of the course of crystallization and an identification of the crystallized products (XRD, Raman imaging technique). Performed investigations revealed that obtaining amorphous materials is only possible in the system containing MgO as a alkaline earth glass modifier, whereas melts of other tested compositions display high tendency to crystallize during cooling. Thermal investigation showed that the influence of SO3addition on thermal properties of studied materials strongly depends on their composition, but generally such additive increased values of glass transformation temperature and decreased vitreous state transformation range and onset of the crystallization process, compared to the base samples, which is a signal of decrease in thermal stability. Examination of devitrificates revealed the character and distribution of domains present in the structure of studied materials. It was showed that irrespective of composition of the base glass, it is K2SO4that precipitates once the sulphate capacity of glass is exceeded and exists in the studied materials as groupings either distributed in the voids of silicate phase, or surrounding the remnants of the gas bubbles embodied within the glass body. The results demonstrated in the present study provide guiding suggestions for development of SO3-containing silicate–phosphate glasses intended especially for applications where release of bioactive ions is sought.
16 March 2024 in Journal of Thermal Analysis and Calorimetry
Vitreous carriers of essential nutrients should release elements in response to plant demand, minimizing over-fertilization risks. This study focused on designing and characterizing sulfate-bearing slow-release fertilizers based on four glass series (41SiO2∙6(10)P2O5∙20K2O–33(29)MgO/CaO/MgO + CaO) with increasing sulfate content. Structural analysis identified a network dominated by units, with some species and isolated units. This fragmented structure resulted in high solubility in acidic environments while maintaining water resistance. Such dual behavior is a direct consequence of the delicate balance between depolymerized silicate chains and isolated orthophosphate units, which ensure rapid ion exchange under acidic conditions while preventing uncontrolled leaching in neutral media. Nutrient leaching depended on SO3 content, affecting matrix rigidity, and on the type of alkaline earth modifier and P2O5 content. Dissolution kinetics showed an initial rapid release phase, followed by stabilization governed by silicate hydrolysis. Thermal analysis linked network flexibility to dissolution behavior—CaO promoted an open structure with high SiO2 release, MgO increased rigidity, while their co-addition reduced ion diffusion and silica dissolution. The thermal behavior of the glasses provided indirect insight into their structural rigidity, revealing how compositional variations influence the mechanical stability of the network. This structural rigidity, inferred from glass transition and crystallization phenomena, was found to correlate with the selective dissolution profiles observed in acidic versus neutral environments. These results reveal complex interactions between composition, structure, and nutrient release, shaping the agricultural potential of these glasses.