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Publikacje z roku 2022

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The effect of paleo-environment on hydrocarbon generation potential: Example from Vaca Muerta Formation, Neuquén Basin, Argentina
- Aleksandra Małachowska
- Grzegorz Lis
- Maria Mastalerz
- Fariborz Goodarzi
- Hamed Sanei
2022 JOURNAL OF PETROLEUM SCIENCE AND ENGINEERING
A 137-m continuous core from the Jurassic-Early Cretaceous marine derived oil shale with the maturity Ro about 0.7 %, representing the oil window in the Vaca Muerta Formation, Neuquén Basin, Argentina, was examined using geological, mineralogical, petrographic, and geochemistry techniques. Three distinct intervals were identified within the core: the upper carbonate-rich section with intense bioturbation, indicating dysoxic to oxic conditions that resulted in poor organic matter preservation; a middle section with decreasing carbonate content, suboxic bottom conditions, and higher organic matter content; and a lower section with higher detrital input and low carbonate content, suboxic to anoxic water conditions, and enhanced preservation of organic matter. Based on the presence of indicator fossils and geochemical parameters, a general trend of increasing organic matter content with lower paleo-oxygen levels was observed. The proportion of solid bitumen within organic matter increases with decreasing oxygen content, suggesting that organic matter deposited in anoxic conditions is more prone to transformation and hydrocarbon generation. There is a negative impact of increasing paleo-oxygen levels on the quantity and quality of organic matter, represented by its potential to generate hydrocarbons.
The effect of shear deformations' rotary inertia on the vibrating response of multi-physic composite beam-like actuators
- Mohammad Malikan
- Victor Eremeev
2022 Pełny tekst COMPOSITE STRUCTURES
In consecutive studies on flexomagneticity (FM), this work investigates the flexomagnetic reaction of a vibrating squared multi-physic beam in finite dimensions. It is assumed that the bending and shear deformations cause rotary inertia. In the standard type of the Timoshenko beam the rotary inertia originated from shear deformations has been typically omitted. It means the rotary inertia resulting from shear deformation is a new concept considered here. Thus, the novelty in this work is that the effect of shear deformation's rotary inertia (SDRI) on the FM response will be considered in detail. When it comes to nanosize, the well-posed nonlocal elasticity assumption of Eringen can be worth choosing. In this study, the weak form of strain-driven nonlocal theory, which means differential form, is taken into hand for easiness. The procedure of solution will be in regard to the advantage of the Galerkin weighted residual technique based on an analytical flow for the meta beam located at simply-simply ends. Verifications of the mathematical model and solving steps come through macro and nanobeams concerning reputable literature. In pursuit of this step, several separate studies will show how SDRI and FM can influence each other. The observations give some new achievements in the series of studies on FM. It has been earned that the SDRI can directly impress the flexomagnetic feature of small-scale actuators.
The Effect of Sodium Tetrafluoroborate on the Properties of Conversion Coatings Formed on the AZ91D Magnesium Alloy by Plasma Electrolytic Oxidation
- Lukasz Florczak
- Ginter Nawrat
- Kazimierz Darowicki
- Jacek Ryl
- Jan Sieniawski
- Małgorzata Wierzbińska
- Krzysztof Raga
- Andrzej Sobkowiak
2022 Pełny tekst Processes
Magnesium and its alloys are widely used in many areas because of their light weight, excellent dimensional stability, and high strength-to-weight ratio. However, the material exhibits poor wear and corrosion resistance, which limits its use. Plasma electrolytic oxidation (PEO) is an effective surface modification method for producing ceramic oxide layers on Mg and their alloys. The influence of the additions of sodium tetrafluoroborate (NaBF4) and sodium fluoride (NaF) into alkaline-silicate electrolyte on the properties of the conversion layers formed in the magnesium AZ91D alloy has been investigated. Surface morphology and chemical composition were determined by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The anticorrosive properties of the layers were evaluated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) methods in simulated body fluid (SBF). The presence of NaBF4 or NaF in the electrolyte increases the corrosion resistance of the protective layer. However, the best anticorrosive properties show the layers obtained in the presence of NaBF4. This is probably caused by the incorporation of boron and fluorine in the form of Mg (BF4)2 mainly in the barrier layer.
The effect of Sr and Mg substitutions on structure, mechanical properties and solubility of fluorapatite ceramics for biomedical applications
- Mohammad Ghaemi
- Sergiy Y. Sayenko
- Volodymyr Shkuropatenko
- Anna Zykova
- Kateryna Ulybkina
- Olena Bereznyak
- Andrzej Krupa
- Mirosław Sawczak
2022 Pełny tekst Processing and Application of Ceramics
Ionic substitutions play important role in the modifications of biological apatites. Recently, attention has been focused on the co-doping effects on the functional properties of apatite-based biomaterials. In this research work, the dense samples of fluorapatites, Ca10(PO4)6F2 and Ca8MgSr(PO4)6F2, were produced after sintering at 1250 °C for 6 h in air. Structural characterization carried out with XRD, IR, Raman and SEM, confirmed the formation of a dense and homogeneous structure with main fluorapatite and a small amount of Ca3(PO4)2 phase. The presented results also demonstrate the stability of structural and mechanical properties of fluorapatites after immersion tests in saline and buffer solutions. The durability of mechanical properties and biocompatibility of the Ca10(PO4)6F2 and Ca8MgSr(PO4)6F2 fluorapatites make these materials highly attractive for biomedical applications.
The Effectiveness of Rubber Bumpers in Reducing the Effects of Earthquake-Induced Pounding between Base-Isolated Buildings
- Khatami Mohamma Seyed
- Hosein Naderpour
- Alireza Mortezaei
- Alireza Sharbatdar
- Natalia Lasowicz
- Robert Jankowski
2022 Pełny tekst Applied Sciences-Basel
Th e methods for preventing earthquake-induced structural pounding between two adjacent buildings include ensuring a sufficient separation distance between them or decreasing their relative displacement during seismic excitation. Some equations or even specific values of such gap sizes between two buildings have been introduced so as to avoid collisions. Increasing the stiffness of buildings, using tuned mass dampers, applying liquid dampers, or decreasing the mass of the structures may reduce lateral displacements, and therefore pounding can be prevented. On the other hand, the application of base isolation systems may result in the elongation of the natural period of the building, thus increasing the probability of structural pounding. The aim of the present paper is to verify the effectiveness of using rubber bumpers to reduce the negative effects of earthquake- induced pounding between base-isolated buildings. The analysis was conducted for different gap sizes between buildings, as well as for various values of the thickness, number and stiffness of rubber bumpers. The results of the study show that the peak impact force decreases with increasing thickness, stiffness, and number of bumpers. Moreover, the peak impact forces are reduced with increasing gap size. The results of the investigation clearly indicate that the use of additional rubber bumpers can be considered an effective method for reducing the negative effects of earthquake-induced pounding between base-isolated buildings.
The Effects of Pin Profile on HDPE Thermomechanical Phenomena during FSW
- Hassanein I. Khalaf
- Raheem Al-Sabur
- Murat Demiral
- Jacek Tomków
- Jerzy Łabanowski
- Mahmoud E. Abdullah
- Hamed Aghajani Derazkola
2022 Pełny tekst Polymers
Friction stir welding (FSW) of polymeric materials has recently attracted significant attention. Herein, we present the effect of the tool pin profile on the FSW of high-density polyethylene (HDPE) joints through joint experimental analysis and thermomechanical simulations. For analysis of pin profile effects on the thermomechanical properties of HDPE joints, frustum (FPT), cubic (CPT), and triangular (TPT) pin shapes were selected in this study. This research investigated the heat generation of the parts of the different tools as well as heat flux (internal and surface). The results revealed that the heat generation in pins with more edges (cubic (96 °C) and triangular (94 °C)) was greater than in pins with a smooth shape (frustum (91 °C)). The higher heat generation caused the heat flux on the surface of the HDPE from the cubic pin profile to be greater than for other joints. Due to the properties of HDPE, higher heat generation caused higher material velocity in the stirring zone, where the velocity of the materials in TPT, CPT, and FPT pins were 0.41 m/s, 0.42 m/s, and 0.4 m/s, respectively. The simulation results show sharp-edged pins, such as triangular and cubic, lead to over-stirring action and internal voids formed along the joint line. Furthermore, the simulation results indicated that the size of the stirred zones (SZs) of the FPT, TPT, and CPT samples were 17 mm2, 19 mm2, and 21 mm2, respectively, which is around three times the corresponding values in the HAZ.
The effects of relational and psychological capital on work engagement: the mediation of learning goal orientation
- Malgorzata Rozkwitalska
- Beata Basińska
- Fevzi Okumus
- Osman M. Karatepe
2022 Pełny tekst JOURNAL OF ORGANIZATIONAL CHANGE MANAGEMENT
Purpose – This paper proposes a research model in which learning goal orientation (LGO) mediates the impacts of relational capital and psychological capital (PsyCap) on work engagement. Design/methodology/approach – Data obtained from 475 managers and employees in the manufacturing and service industries in Poland were utilized to assess the linkages given above. Common method variance was controlled by the unmeasured latent method factor technique. Findings – LGO mediates the impact of PsyCap on work engagement. More specifically, employees high on PsyCap are more learning goal-oriented, and therefore are work-engaged at elevated levels. Employees also exhibit higher work engagement as a result of their relational capital. Research limitations/implications – This study extends the research stream on the interrelationships of relational capital, PsyCap, LGO and work engagement to Poland. It fills a void in the relevant literature. Yet, the authors collected cross-sectional, self-report data in a single country. Practical implications – Manufacturing and service companies in Poland should create and maintain a work environment where managers and employees develop trust and high-quality relationships with their managers and coworkers and invest in their personal resources. In addition, management should arrange continuous training programs so that employees can continue developing themselves. Such practices are critical in an organization where employees’ work engagement is triggered by relational capital, PsyCap and LGO. Originality/value – This paper enhances the current literature by exploring relational capital, PsyCap and LGO simultaneously as the predictors of work engagement, which have been subjected to limited empirical inquiry. The paper also extends the research stream about the above-mentioned predictors of engagement to Poland, which is an underrepresented country in the field of human resource management.
The Efficacious Benefit of 25-Hydroxy Vitamin D to Prevent COVID-19: An In-Silico Study Targeting SARS-CoV-2 Spike Protein
- Tomy Muringayil
- Akshay M S
- Debarshi Kar Mahapatra
- Józef Haponiuk
- Sabu Thomas
2022 Pełny tekst Nutrients
The environment has rapidly looked at proven specialist task forces in the aftermath of the COVID-19 pandemic to build public health policies and measures to mitigate the effects of emerging coronaviruses. According to the researchers, taking 10 μg of 25-hydroxy vitamin D daily is recommended to keep us safe. There have been several studies recently indicating that there is a reduced risk of contracting Coronavirus by 25-hydroxy vitamin D consumption, even though there is no scientific data to prove that one would not affect the COVID-19 viral infection by 25-hydroxy vitamin D consumption. In this regard, the present study investigates the important literature and the role of 25-hydroxy vitamin D to prevent COVID-19 infection by conducting an in-silico study with SARS-CoV-2 spike protein as a target. Lopinavir, a previously reported drug candidate, served as a reference standard for the study. MD simulations were carried out to improve predictions of receptor-ligand complexes which offer novelty and strength to the current study. MD simulation protocols were explored and subjected to 25-hydroxy vitamin D and a known drug, Lopinavir. Comparison of ligands at refined models to the crystal structure led to promising results. Appropriate timescale simulations have been used to understand the activation mechanism, the role of water networks for receptor function, and the ligand binding process. Furthermore, MD simulations in combination with free energy calculations have also been carried out for lead optimization, evaluation of ligand binding modes, and assessment of ligand selectivity. From the results, 25-hydroxy vitamin D was discovered to have the vital interaction and highest potency in LBE, lower RMSD, and lower inhibition intensity similar to the standard. The findings from the current study suggested that 25-hydroxy vitamin D would be more effective in treating COVID-19. Compared with Lopinavir, 25-hydroxy vitamin D had the most potent interaction with the putative binding sites of the SARS-CoV-2 spike protein of COVID-19.
The electrical, morphological and optical properties of heavily boron-doped diamond sheets as a function of methane concentration in the gas phase
- Michał Rycewicz
- Adrian Nosek
- Mirosław Sawczak
- Jacek Ryl
- Robert Bogdanowicz
2022 Proceedings of SPIE
Boron-doped diamonds (BDD) are known for their excellent properties such as high thermal conductivity, high mobility, low absorption in visible light, and biocompatibility. In this work, we investigated the electrical, morphological and optical properties of heavily boron-doped diamond thin sheets as a function of methane concentration in the gas phase. Free-standing diamond sheets were fabricated using a microwave plasma-assisted chemical vapor deposition. The methane concentration was controlled by adding CH4 (up to 4%) to the gas phase, while the [B]/[C] ratio was 20,000 ppm. The samples grown with a higher methane concentration show more defects providing additional conduction paths. As a result, the lowest resistance was observed for the sample with a 4% methane concentration in the gas phase. Morphological studies suggest that a strong increase in the standard deviation of grain size and larger thickness of films is correlated with a higher sp2 phase. Moreover, an increase of disordered carbon content is accompanied by a lower transparency of the BDD sheets. This experiment could serve as a stepping stone in the future production of highly conductive large-area boron-doped diamond sheets.
The energy approach to fatigue crack growth of S355 steel welded specimens subjected to bending
- Dariusz Rozumek
- Janusz Lewandowski
- Grzegorz Lesiuk
- Zbigniew Marciniak
- José A.F.O. Correia
- Wojciech Macek
2022 Pełny tekst THEORETICAL AND APPLIED FRACTURE MECHANICS
The study presents the results of the research on the rate of fatigue crack growth subjected to bending in the ferritic-pearlitic structure. The studies were carried out at a constant amplitude of the moment and at various values of the load ratios R and at the operating frequency of the machine of 28.4 Hz. Flat specimens made of S355 steel and with fillet welds and with double-sided blunt external notches as well as concave and convex welds were tested. The tests were performed on specimens without and after relief annealing. The study showed that the heat treatment had an influence on the dispersion of the test results described by the energy parameter. It was also observed that the effect of the applied treatment increased the rate of fatigue crack growth.
The Energy Potential of the Lower Vistula River in the Context of the Adaptation of Polish Inland Waterways to the Standards of Routes of International Importance
- Krzysztof Woś
- Krzystof Wrzosek
- Tomasz Kolerski
2022 Pełny tekst ENERGIES
Based on new policies of the European Union, green technologies are to be mostly considered for power generation. Hydropower generation is one of the essential elements of sustainable energy production. Therefore, specific attention, both economically and technically, needs to be given to this sector of energy production. The Vistula River in Poland is considered an international waterway. The power production potential of the river has been taken into account over the years. However, further configurations are needed to obtain a more in-depth ecological knowledge-base and economic plans, which are socially approved. In an attempt to make the project environmentally friendly, specific attention was put into sustainable transport. Different methods of transport were researched to find the most renewable transport combination, mainly based on waterways. Having performed a cost–benefit analysis related to the economic aspects of the project, it was found that such an investment is highly profitable (B/C = 2.81).
The Environmental Benefits of Photovoltaic Systems: The Impact on the Environment in the Production of Photovoltaic Systems: With a Focus on Metal Recovery
- Ewa Klugmann-Radziemska
2022
Greenhouse gases (GHGs) such as carbon dioxide, nitrous oxide and methane, trap heat and energy, thus preventing solar radiation from escaping back into space. As the quantity of greenhouse gases in the atmosphere increases so does the trapped heat and corresponding global temperature. As a result, storms become more violent, droughts more prevalent, glaciers melt, and sea levels rise, to name but a few effects of a rapidly changing climate. These unfavorable climate changes observed for many years have provided an incentive for the development of renewable energy sources, in particular those technologies, that serve the production of electricity. The use of photovoltaic modules to convert solar radiation into electricity results in a reduction of harmful GHGs, characteristic of traditional fossil fuel technologies, and furthermore, leads to economic benefits and independence of energy supplies. Analyzing the complete life cycle of photovoltaic modules: the process of production, operation, and the recycling of solar cell panels and ancillary components, one can demonstrate obvious environmental benefits, justifying not only the costs of photovoltaic technology development, but also government's actions in support of solar panels. Depending on the technology used, the production phase of photovoltaic modules does burden the environment to varying degrees, but overall there are incomparable gains to be made by exploiting photovoltaic systems for electricity production. Waste management and the re-use of valuable materials can also significantly improve the final environmental balance. As the photovoltaic market is still growing, it is important at this stage, to assess the long-term impact of PV technology on the natural environment. In this chapter, the impacts of using photovoltaic solar modules for energy production on the natural environment, are discussed.
The EU Tyre Noise Label: The problem with measuring the noise level of only a few of all tyre variants
- Ulf Sandberg
- Piotr Mioduszewski
2022
The STEER project, described in another Inter-Noise 2022 paper, has evaluated the performance of the noise label of the European tyre label. The major finding was that uncertainties of the tyre/road noise measurements were higher than should be accepted. One of the worst uncertainty sources was found to be the common practice to measure only some tyres of all sizes or variants within a tyre line, to save money. Generally, only the noisiest tyre(s) is/are measured individually and other tyres in that line get the same level, which means that many if not most tyres are labelled with too high noise levels. Then consumers cannot find the quietest tyres. STEER lacked resources to study this problem, but a Swedish project supported STEER in this respect, by making it possible to measure noise of 53 tyres selected from tyre lines of three major tyre manufacturers. The results showed that even though tyres in each line were labelled with the same noise level, in practice they differed up to 6 dB in noise emission. To avoid this very serious source of uncertainty, a special simplified test is suggested in order to be able to label tyres correctly without too much extra effort.
The Impact of a New Product’s Novelty and Meaningfulness on its Commercial Performance
- Dariusz Dąbrowski
2022 Pełny tekst IBIMA Business Review
s new product development (NPD) process encompasses creative actions, so a new product is characterized by two essential dimensions used to describe any creative output – namely novelty and meaningfulness. Therefore, businesses are faced with the questions to what extent and under what market conditions to develop each of these dimensions in order to obtain high new product commercial performance. Based on gaps indentified in the new product literature and drawing on the resource-based view as well as signaling theory, this study addresses three following aims. The first one is to revisit the impact of a new product’s meaningfulness and novelty on its commercial performance; the second one is to compare the relative influence of these dimensions on this performance; and the third one is to examine the moderating effect of market turbulence on the relationship between the novelty and the new product’s commercial performance. These goals were achieved by analyzing data concerning 374 new products of Polish high- and medium-high-technology companies with the use of structural equation modeling. This study finds that a new product’s meaningfulness is positively related to its commercial performance, while novelty is not. Furthermore, meaningfulness affects this performance more strongly than product novelty. It is also found that market turbulence moderates the relation between the new product’s novelty and performance such that this association is stronger when market turbulence is high compared to when it is low. The paper concludes with theoretical and managerial implications about how firms can benefit and under what market conditions from creativity.
The impact of bankruptcy regimes on entrepreneurship and innovation. Is there any relationship?
- Błażej Prusak
- Sylwia Morawska
- Przemysław Banasik
- Michał Łukowski
2022 Pełny tekst International Entrepreneurship and Management Journal
The literature review indicates that bankruptcy law may play an important role in and be one of the factors infuencing the development of entrepreneurship, innovation, and thus economic growth, among other things. In previous studies, the analysis of the impact of bankruptcy law on individual variables has been conducted independently. Our aim was to conduct a holistic analysis, taking several factors into account simultaneously. Therefore, a descriptive model was proposed, based on which the following research hypothesis was formulated: In countries characterised by an efective legal system and at the same time debtor-friendly bankruptcy law, the level of risk acceptance among entrepreneurs is higher, which is refected in higher levels of entrepreneurship and innovation. Based on the selected variables, a cross-sectional analysis was conducted using linear models estimated on the basis of the least-squares method. Additionally, to strengthen the conclusions drawn, the models were assessed in such a way enabling the analysis of causality as defned by Granger based on the two-step process. The results obtained allowed us to confrm the research hypothesis: in countries characterised by an efcient legal system and at the same time debtor-friendly bankruptcy law, the level of risk acceptance among entrepreneurs is higher, which is refected in higher levels of entrepreneurship and innovation. The research results are particularly important from the point of view of legislators who are responsible for drafting amendments to bankruptcy law. Including certain debtor-friendly provisions may, in the long run, lead to increased entrepreneurship and innovation, and thus economic development.
The impact of cold plasma on the phenolic composition and biogenic amine content of red wine
- Iwona Niedźwiedź
- Justyna Płotka-Wasylka
- Ireneusz Kapusta
- Vasil Simeonov
- Anna Stój
- Adam Waśko
- Joanna Pawłat
- Magdalena Polak-Berecka
2022 Pełny tekst FOOD CHEMISTRY
The effect of cold plasma (CP) on phenolic compound (PC) and biogenic amine (BA) contents of red wine was investigated for the first time. The influence of CP was compared with the effects of a wine preservation using potassium metabisulfite and a combined method. The PC profile was determined by UPLC-PDA-MS/MS while BAs using DLLME-GC–MS. Chemometric analysis also was used. The content of PCs was 3.1% higher in the sample preserved by CP treatment (5 min, helium/nitrogen) compared to a sample preserved by the addition of potassium metabisulfite (100 mg/L). On a positive note, CP treatment reduced the concentration of BAs in the wine samples. The lowest BA contents were recorded after 10 min of cold plasma (helium/oxygen) treatment with the addition of potassium metabisulfite (1120.85 μg/L). The results may promote interest in CP as a potential alternative method for the preservation of wine and other alcoholic beverages
The impact of footing conditions of a vertical-axis floating-roof tank on structural shell deformation
- Kamil Żyliński
- Jarosław Górski
2022 Pełny tekst
Structural shells of fuel tanks are often subjected to geometric imperfections which may lead to exceeding the ultimate and serviceability limit states. One of the means triggering shell deformation is non-uniform settlement caused by incoherent soil conditions. Analysis carried out in the work concerns of vertical-axis, floating-roof cylindrical shell which volume is 50.000 m3, founded on a complex multi-layered soil. The sensitivity analysis was conducted of a tank settlement due to variation of material soil parameters and the strata layout. It reads that even in the case of extremely disadvantageous material data the structure is not bound to exceed the serviceability limit states.
The impact of institutions on innovation networks: empirical evidence from Poland
- Przemysław Banasik
- Sylwia Morawska
- Małgorzata Godlewska
2022 Pełny tekst Technological and Economic Development of Economy
Innovation networks may accelerate and improve the innovation process, while institutional pathologies may hamper it. This study employs the Kruskal-Wallis H test and regression analysis to determine if the relationship between institutions and innovation networks does exist among the investigated variables. The purpose of the study was to find out whether cooperation with special local institutions influences the innovative behaviour of local governments manifested by participation in innovation networks or innovation networks based on formal institutions limit institutional pathologies better than informal ones. Current paper presents results of an empirical study conducted through survey among all local governments in Poland. The findings show that previous cooperation with special local institutions influences the innovation behaviour of local governments or innovation networks based on formal rules limit the institutional pathologies of innovation networks better than those based on sanctions, common values, codes of ethics, governance codes or culture. The investigated problem is significant, as properly functioning innovation networks may generate incremental innovations, which may help to solve the contemporary challenges. The practical implications for national regulatory bodies highlight the need for an enforcement mechanism which may support the formalisation of innovation networks.
The impact of interactions between polyphenolic antioxidants on the redox-related chemical and biological properties of their mixtures – the extension of food synergy concept.
- Monika Baranowska
2022
The results of studies indicate that chemopreventive efficiency of isolated phytochemicals is lower than that of polyphenol-rich foods. This discrepancy has been ascribed to the food synergy concept that assumes additive or even synergistic influence of different food ingredients on human health. The results presented in the dissertation made it possible to propose an alternative and innovative explanation of these observations. The research carried out within the frame of PhD project has shown that properties of polyphenol mixtures are not just the combination of enhanced or weakened activities displayed by individual components. The study revealed the pronounced impact of interactions between polyphenols on redox-related biological activities. This was enabled owing to the wide range of methods used, including the assessment of cellular antioxidant activity, cytotoxicity, genotoxicity, epigenetic and nutrigenomic activity using a human colon adenocarcinoma cell line exposed to either pure compounds, model mixtures or natural extracts. These studies led to the formulation of the thesis that the activity of a mixture of polyphenols is dictated by interactions between the components, which creates a new substance displaying modified chemical and physicochemical properties resulting in unique biological effects.
The Impact of Isocyanate Index and Filler Functionalities on the Performance of Flexible Foamed Polyurethane/Ground Tire Rubber Composites
- Adam Olszewski
- Paulina Kosmela
- Adam Piasecki
- Mateusz Barczewski
- Aleksander Hejna
2022 Pełny tekst Polymers
The structure and performance of polyurethane (PU) foams are strongly driven by the stoichiometry of the polyaddition reaction, quantitatively described by the isocyanate index. It determines the balance between isocyanate and hydroxyl groups in the reacting system and is affected by the introduction of additional functionalities originated, e.g., from applied fillers. Nevertheless, this issue is hardly taken into account in research works. Herein, the structure and performance of PU/ground tire rubber (GTR) composites differing in their isocyanate index (from 0.8 to 1.2) and prepared with and without considering the GTR functionalities in formulation development were investigated. Incorporating GTR into the PU matrix led to a reduction in average cell diameter (from 2 to 30% depending on the isocyanate index) compared to unfilled foams. However, formulation adjustments did not show a significant impact on cellular structure. The only decrease in open cell content was noted, from 10% for the 0.9 index to 40% for 1.2. Such changes were related to the increasing strength of the PU cellular structure able to maintain inside the increasing amount of carbon dioxide. On the other hand, considering hydroxyl values of GTR noticeably affected the thermomechanical performance of composites. The shift of glass transition temperature (Tg), even by 10 °C for 1.2 isocyanate index, enhanced the performance of materials, which was expressed in an 8–62% drop in the composite performance factor, pointing to the enhanced reinforcing effect resulting from filler incorporation. The stiffening of foams, related to the variations in PU segmental structure, also caused minor changes in the course of thermal degradation of PU/GTR composites due to the inferior thermal stability of hard segments. The obtained results provide important insights into the development of formulations of PU composites filled with materials containing reactive functional groups able to disrupt the stoichiometric balance of the polyaddition reaction.