A fairly simple yet efficient quantitative protocol was developed to investigate plant composition using Fourier-transform infrared spectroscopy (FTIR), through biomass analysis arising from the whole shoot system of Cardoon (Cynara cardunculus L.), Cannabis (Cannabis sativa L.) and Switchgrass (Panicum virgatum L.). An analytical compositional report of the biomasses, serving as a standard method to identify the different chemical groups present, was compared with relevant FTIR spectra and Thermogravimetric Analysis (TGA) thermographs. In order to interpret the highly convoluted absorption spectra, not only a series of reference materials were examined but also extraction protocols were implemented to sequentially isolate the compositional units allowing a spectroscopic monitoring of their progressive removal from the biomass. This approach enabled the assignment and distinction of a series of vibrational peaks and regions identified in the lower wavenumber region. These peaks/regions, were found to be capable of quantitating different chemical units, such as lignin, fats and lipids, even in the case of structural polysaccharides, like cellulose, hemicellulose and pectin, which are the primary constituents of plant cells. Fats and lipids were easily detected at the 3050–2800 cm⁻¹ region, with their concentration determined by the isolated 720 cm⁻¹ and the 728 cm⁻¹ peaks, when present. Lignin concentration was determined via the 1508 cm⁻¹ peak. Hemicellulose is contributing to the 1640, 1245 cm⁻¹ as well as the 1740 cm⁻¹ peak, with its concentration determined in the 850–750 cm⁻¹ region. Cellulose content was quantified via the 895 cm⁻¹ peak, while pectin appeared at the 915 cm⁻¹ peak and also contributed to the 1640 cm⁻¹ signal. Consequently, a better understanding of the vibrational convolution could thus be achieved when studying plant cells where multiple structural units contribute to the spectra. It is therefore expected that plant cellular composition can be adequately revealed with a single FTIR spectrum, without the need for intensive analysis methods, offering a faster and more efficient approach.

Hybrid polymeric materials incorporating carbon nanostructures or inorganic constituents stand as a promising class of materials exhibiting distinct but also complementary features. Carbon nanotubes have been proposed as unique candidates for polymer reinforcement; however, sustained efforts are further needed in order to make full use of their potential. The final properties of the reinforced polymer are controlled in part by the morphology and the eventual molecular orientation of the polymer matrix. In the present study, multiwall carbon nanotubes (MWCNTs) were utilized in order to reinforce polyethylene terephthalate (PET) composites. The effect of CNTs on the crystallization and the orientation of the structurally hybridized polymeric material has been investigated from the perspective of assessing their impact on the final properties of a relevant nanocomposite product. Functionalized MWCNTs were used to achieve their optimal dispersion in the polymer matrix. The physical properties of the composites (i.e., crystallinity and orientation) were characterized via differential scanning calorimetry, X-ray diffraction, and polarized Raman microscopy. The addition of well-dispersed CNTs acted as a nucleation agent, increasing the crystallization of the polyethylene terephthalate matrix and differentiating the orientation of both CNTs and macromolecular chains.

Bio-nanocomposites based on poly (vinyl alcohol) (PVA) and cellulosic nanostructures are favorable for active food packaging applications. The current study systematically investigates the mechanical properties, gas permeation, and swelling parameters of PVA composites with cellulose nanocrystals (CNC) or nano lignocellulose (NLC) fibers. Alterations in these macroscopic properties, which are critical for food packaging applications, are correlated with structural information at the molecular level. Strong interactions between the fillers and polymer host matrix were observed, while the PVA crystallinity exhibited a maximum at ~1% loading. Finally, the orientation of the PVA nanocrystals in the uniaxially stretched samples was found to depend non-monotonically on the CNC loading and draw ratio. Concerning the macroscopic properties of the composites, the swelling properties were reduced for the D1 food simulant, while for water, a considerable decrease was observed only when high NLC loadings were involved. Furthermore, although the water vapor transmission rates are roughly similar for all samples, the CO₂, N₂, and O₂ gas permeabilities are low, exhibiting further decrease in the 1% and 1–5% loading for CNC and NLC composites, respectively. The mechanical properties were considerably altered as a consequence of the good dispersion of the filler, increased crystallinity of the polymer matrix, and morphology of the filler. Thus, up to ~50%/~170% enhancement of the Young’s modulus and up to ~20%/~50% enhancement of the tensile strength are observed for the CNC/NLC composites. Interestingly, the elongation at break is also increased by ~20% for CNC composites, while it is reduced by ~40% for the NLC composites, signifying the favorable/unfavorable interactions of cellulose/lignin with the matrix.

In this study, hybrid nanocomposites consisting of Fe₃O₄/BaTiO₃/epoxy resin were prepared with varying amounts of filer content. Structural and morphological characterization, conducted via X-Ray Diffraction patterns and Scanning Electron Microscopy images, revealed the successful fabrication of composites and fine dispersion of inclusions. Thermomechanical properties are studied via Differential Scanning Calorimetry, Thermogravimetric Analysis, Dynamic Mechanical Analysis and static mechanical tests. Hybrid composites exhibit enhanced thermal stability and improved mechanical response. Indicatively, Young’s modulus, tensile strength and fracture toughness increase from 1.26 GPa, 22.25 MPa, and 3.03 kJ/m³ for the neat epoxy to 1.39 GPa, 45.73 MPa, and 41.08 kJ/m³ for the composites with 20 or 15 parts per hundred resin per mass (phr) of Fe₃O₄, respectively. Electrical behavior is investigated via Broadband Dielectric Spectroscopy and ac conductivity measurements. The real part of dielectric permittivity reaches the value of 11.11 at 30 °C for the composite with 40 phr of Fe₃O₄. The ability to store and retrieve electric energy on the nanocomposites is examined with the following parameters: the filler content and the applied voltage under dc conditions. Retrieved energy reaches 79.23% of the stored one, for the system with 15 phr of Fe₃O₄. Magnetic response is studied via a Vibrating Sample Magnetometer. Magnetic saturation, for the system with the highest magnetic filler content, obtains the value of 25.38 Am²/kg, while pure magnetic powder attains the value of 86.75 Am²/kg. Finally, the multifunctional performance of the nanocomposites is assessed regarding all the exerted stimuli and the optimum behavior is discussed.