Dumitrița Moldovan

The present study explores the transformation of waste packaging plastics high-density polyethylene (HDPE), polypropylene (PP), and polystyrene into combustible condensates through slow pyrolysis at low temperatures, using a custom-built reactor inspired by the Blest machine model. To characterize their structural properties, the original plastic materials, their pyrolysis derivatives, and three conventional liquid fossil fuels were examined using advanced techniques, including ¹ H relaxometry, double quantum nuclear magnetic resonance, and Fourier Transform Infrared spectroscopy. The resulting condensate oils, collected unfiltered, exhibited clear amber shades and demonstrated partially Newtonian fluid behavior. A comparative analysis of their calorific values with traditional fossil fuels revealed that HDPE and PS-derived oils possess viable fuel properties, although the production process remains costly.

Rubber materials undergo structural degradation that can lead to loss of functional performance. In this work, the effects of thermal ageing and uniaxial compression on segmental chain dynamics were investigated for cross-linked natural rubber samples (NR1–NR7) using unilateral NMR relaxometry. Transverse proton relaxation time ( T ₂ ) distributions were obtained by Fast Laplace Inversion of CPMG echo decays measured with a Bruker Minispec spectrometer coupled to a unilateral NMR-MOUSE ^® sensor. Samples were thermally aged at 90 °C for 24 h. Surface ageing was also induced using a 500 °C heat source at 10 cm distance, and the penetration depth of the thermal effect was estimated at ~ 0.6 mm. Results show that T ₂ -distributions depend strongly on cross-link density and ageing conditions. Two relaxation components, short (rigid) and long (mobile), were identified, with the long component showing higher sensitivity to structural changes. A correlation between relaxation parameters and shear modulus confirms the dependence of segmental dynamics on network rigidity. Under uniaxial compression, NR4 exhibited a linear dependence of both T ₂ components on pressure, with higher sensitivity than NR1. This correlates with lower mechanical stiffness and leads to failure of NR4 at ~ 3000 kgf/m², while NR1 remains intact up to 9000 kgf/m². These results demonstrate that unilateral NMR relaxometry is an effective non-destructive tool for probing polymer dynamics and evaluating thermal and mechanical degradation in elastomers, with relevance for material characterization and quality control.

The objective of this study was to determine the structural and textural description of municipal solid waste incineration (MSWI) bottom ash that was subjected to a six-month seasoning process. Bottom ash samples, with a particle size fraction of 0.063–0.1 mm, were seasoned in a closed landfill and collected for laboratory analyses at monthly intervals. The research focused on determining the structural parameters, using methods such as nuclear magnetic resonance spectroscopy (¹H NMR), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-Vis), and the textural parameters, using low-pressure nitrogen adsorption (LPNA) at −196.15 °C. The analyses of the porous structure of the bottom ash samples revealed differences in texture of ASH 1 to ASH 6, specifically in the pore volume (micro- and mesopores), specific surface area, and pore size distribution. Changes in the structural and porous characteristics of the samples were attributed to the duration of the seasoning process. The results of the structural analysis of the bottom ash suggest its application in the concrete industry, potentially enhancing the long-term mechanical strength of concrete. The results of the textural analysis indicate the possible use of MSWI bottom ash in environmental applications, as the internal surface area could be further developed.

Whey and gelatin, natural polymers within the protein category, find widespread use in hydrogel formulations applied across the food, medical, and pharmaceutical industries. This study presents new characteristics of hydrogels based on whey, gelatin, and copper sulfate as a consequence of the additional steps in the preparation method, specifically refrigeration and freezing storage followed by lyophilization. The water state in hydrogels prior to lyophilization impacts the morphological appearance, with refrigerated hydrogels exhibiting a more regular and dense pore distribution, as shown by the Scanning Electron Microscopy (SEM) images. This observation aligns with the higher mobility of polymer chains indicated by T₂ distributions in ¹H nuclear magnetic resonance (RMN) relaxometry measurements. Changes in the intensity and amide-specific wavenumbers of the FTIR spectra of whey and gelatin proteins are evident in the Fourier Transformed Infrared (FTIR) spectra of crosslinked and frozen hydrogels before lyophilization. Moreover, the reinforcing effect in the hydrogel matrix, noted in mechanical tests, is attributed to increased polymer chain content and copper sulfate crosslinking.

Whey-based hydrogel samples with increasing concentrations of graphene oxide (GO) were studied, against a control sample (M), for swelling behavior in light of nuclear magnetic resonance (NMR) and mathematical models of the diffusion process and for antibacterial activity. Graphene oxide (GO) is an optimal filler for whey-based hydrogels, giving them improved mechanical and swelling properties at low concentrations. Crosslinking induces a certain stiffness of the hydrogels, which is why only the first part of the swelling process (<60%) follows the first-order model, while during the whole time interval, the swelling process follows the second-order diffusion model. The NMR relaxometry results are consistent with the swelling behavior of GO-reinforced whey–gelatin composite hydrogels, showing that higher GO concentrations induce a higher degree of cross-linking and, therefore, lower swelling capacity. Only hydrogel samples with higher GO concentrations demonstrated antibacterial activity.

By-products from the meat and dairy industries are important sources of high biological value proteins. This paper explores possibilities for improving the swelling and integrity of a cross-linked whey and gelatin hydrogel with different amounts of CuSO₄ × 5H₂O. Overall, swelling tests demonstrate that cross-linked samples show a better hydration capacity and stability in the hydration medium, but different copper concentrations lead to different swelling behavior. At concentrations smaller than 0.39%, the sample lasts for 75 h in a water environment before beginning to disintegrate. At a concentration of copper sulphate higher than 0.55%, the stability of the sample increased substantially. The swelling kinetics has been investigated. The diffusion constant values increased with the increase in copper concentration, but, at the highest concentration of copper (0.86%), its value has decreased. Spectroscopy analyses such as Fourier transform infrared (FT-IR), X-ray diffraction (XRD), ultraviolet-visible spectroscopy (UV-VIS), and nuclear magnetic resonance (NMR) relaxometry analyses revealed changes in the secondary and tertiary structure of proteins as a result of the interaction of Cu²⁺ ions with functional groups of protein chains. In addition to its cross-linking ability, CuSO₄ × 5H₂O has also shown excellent antibacterial properties over common bacterial strains responsible for food spoilage. The result of this research demonstrates the potential of this hydrogel system as a unique material for food packaging.

The ¹H DQ Fourier and Laplace-like spectra for a series of cross-linked natural rubber (NR) samples naturally aged during six years are presented and characterized. The DQ build-up curves of these samples present two peaks which cannot be described by classical functions. The DQ Fourier spectra can be obtained after a numeric procedure which introduces a correction time which depends less on the chosen approximation, spin-½ and isolated CH₂ and CH₃ functional groups. The DQ Fourier spectra are well described by the distributions of the residual dipolar coupling correlated with the distribution of the end-to-end vector of the polymer network, and with the second and fourth van Vleck moments. The deconvolution of DQ Fourier spectra with a sum of four Gaussian variates show that the center and the width of Gaussian functions increase linearly with the increase in the cross-link density. The Laplace-like spectra for the natural aged NR DQ build-up curves are presented. The centers of four Gaussian distributions obtained via both methods are consistent. The differences between the Fourier and Laplace-like spectra consist mainly of the spectral resolution in the favor of Laplace-like spectra. The last one was used to discuss the effect of natural aging for cross-linked NR.

Microscopic properties like network dynamics and phase compositions were studied for a series of commercially available cosmetics emulsions like hair shampoo, anti-UV shielding creams and hand and body creams. Proton longitudinal and transverse nuclear magnetic relaxations were measured by recording the 1D CPMG and 2D saturation recovery–CPMG echoes decays. The one and bi-dimensional inverse Laplace transformations reveals subtitle features which characterize the microscopic dynamic behaviour associated with the in vitro natural degradation of cosmetics. The IR and UV–VIS spectra were recorded and correlated with the NMR measurement.