Thermal and Mechanical Properties of Microporous Polyurethanes Modified with Reduced Graphene Oxide

Microporous polyurethanes (MPU) were modified by adding 0.25%–1.25 wt% of reduced graphene oxide (RGO). The materials were prepared without solvent via in situ polymerization. From a technological point of view, it is very important to obtain functional materials by using reacting compounds only. The thermal characteristics of obtained MPU were investigated using TGA, DSC, and DMA techniques. In comparison to nonmodified microporous polyurethane, the thermal stability and mechanical properties of the modified systems have significantly improved. The temperature corresponding to the maximum degradation rate (Tmax) for nanocomposites containing 1% and 1.25 wt% of RGO was 51°C higher than that observed for pure microporous PU system. The increase of tensile strength was also observed for matrix with the addition of 0.5 wt% RGO nanofiller

Quantifying damping coefficient and attenuation at different frequencies for graphene modified polyurethane by drop ball test

In this study, polyurethane (PU) was modified by direct mixing of carboxyl functionalised graphene (GNP–COOH) referred to as f-GNP, without using any solvent, during in-situ polymerization. In a further attempt, the neat PU was modified with f-GNP and a hydrophobic silica-based solution (SG) during in-situ polymerization. The damping coefficient and attenuation capacity of neat polyurethane (PU), f-GNP based PU nanocomposite (PU + f-GNP), and f-GNP and hydrophobic silica-based solution PU nanocomposite (PU + f-GNP + SG), together with polytetrafluoroethylene (PTFE), high-density polyethylene (HDPE), ultra-high molecular weight polyethylene (UHMWPE), polyethylene terephthalate (PET), polyvinyl chloride (PVC) and NYLON have been obtained by the drop ball tests under controlled and consistent conditions. The results show that among the tested materials, polyurethane modified with carboxyl functionalised graphene and silica-based Sol-Gel (PU + f-GNP + SG) displays the greatest attenuations and PTFE the least.The attenuation of the various materials has been identified with the SVD-QR method. This experimental modal analysis method has been used to analyse the free response signal of the system during the drop ball test and identify the modal parameters such as damping ratio and frequency of the modes of deformation of the system. The drop ball test results show that the damping coefficient of polyurethane modified with 0.5 wt% carboxyl functionalised graphene (PU + f-GNP) increased by 37% at frequency range 200–300 Hz, by 34% at frequency range 500–600 Hz and by 32% at frequency range 700–1000 Hz. The developed nanocomposite materials have great potential for protecting leading edge erosion (LEE) of wind turbine

Zagrożenia w przepowiadaniu Słowa Bożego w świetle "Enarrationes in psalmos" św. Augustyna

This article shows the dangers in preaching of God’s word according to St. Augustine. The observations of the Bishop of Hippona are double. In the first group there are exterior dangers. Their source of origin is on the outside of the Church, from heretics and schismatics. In the second group there are internal dan­gers. Their source is in human dimension of the Church. Among them, according to St. Augustine, there are: preachers-mercennnaries, excessive pride of preacher, desire of human praises and honours, laziness in God’s service, giving into temp­tation of earthly comfort and care for worldly things.</jats:p

Effect of Variation of Hard Segment Content and Graphene-Based Nanofiller Concentration on Morphological, Thermal, and Mechanical Properties of Polyurethane Nanocomposites

This study describes the development of a new class of high-performance polyurethane elastomer nanocomposites containing reduced graphene oxide (RGO) or graphene nanoplatelets (GNP). Two types of polyurethane elastomers with different contents of hard segments (HS) were used as a polymer matrix. The developed nanocomposites were characterized by thermal analysis (DSC, TG), dynamic mechanical testing (DMA), hardness testing, mechanical properties, rheology, FTIR spectroscopy, XRD, and microscopy investigation (TEM, SEM). Morphological investigation confirmed better compatibility of RGO with the polyurethane (PU) matrix compared to GNP. Both applied nanofillers influenced melting and crystallization of the PU matrix. The nonlinear viscoelastic behavior of the nanocomposites (Payne effect) was studied, and the results were compared with theoretical predictions

Dangers in the preaching of God’s word in the light of saint Augustine’s Enarrationes in psalmos

This article shows the dangers in preaching of God’s word according to St. Augustine. The observations of the Bishop of Hippona are double. In the first group there are exterior dangers. Their source of origin is on the outside of the Church, from heretics and schismatics. In the second group there are internal dangers. Their source is in human dimension of the Church. Among them, according to St. Augustine, there are: preachers-mercennnaries, excessive pride of preacher, desire of human praises and honours, laziness in God’s service, giving into temptation of earthly comfort and care for worldly things

Morphology, Mechanical and Thermal Properties of Thermoplastic Polyurethane Containing Reduced Graphene Oxide and Graphene Nanoplatelets

Polyurethane/graphene nanocomposites were synthesized using commercial thermoplastic polyurethane (TPU, Apilon 52DE55), and two types of graphene derivatives: graphene nanoplatelets (GNP) and reduced graphene oxide (RGO). Fourier Transformation Infrared Spectroscopy Fourier Transformation Infrared Spectroscopy (FTIR) spectroscopy, TEM, and SEM microscopy and XRD techniques were used to chemically and structurally characterize GNP and RGO nanofillers. The properties of the new TPU nanocomposite materials were studied using thermal analysis techniques (Dynamical Mechanical Analysis (DMA), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TG)) to describe the influence of graphene nanofillers on polyurethane matrix. Our investigation describes the comparison of two types of graphene derivatives, commercial one (GNP) and synthesized (RGO) on thermoplastic polyurethanes. These nanofillers provides opportunities to achieve compatibility with the TPU matrix. The property enhancements are attributed commonly to high aspect ratio of graphene nanoplatelets and filler–polymer interactions at the interface. The obtained nanocomposites exhibit higher thermal and mechanical properties due to the good dispersion of both nanofillers into TPU matrix. It was found that the addition of 2 wt % of the nanofiller could lead to a significant reinforcement effect on the TPU matrix. Also, with high content of nanofiller (GNP and RGO), the Payne effect was observed