Composites of Poly(3-hydroxybutyrate) and Mesoporous SBA-15 Silica: Crystalline Characteristics, Confinement and Final Properties.

Several composites based on poly(3-hydroxybutyrate) (PHB) and mesoporous SBA-15 silica were prepared by solvent-casting followed by a further stage of compression molding. The thermal stability, phase transitions and crystalline details of these composites were studied, paying special attention to the confinement of the PHB polymeric chains into the mesopores of the silica. For that, differential scanning calorimetry (DSC) and real-time variable-temperature X-ray scattering at small angles (SAXS) were performed. Confinement was stated first by the existence of a small endotherm at temperatures around 20 °C below the main melting or crystallization peak, being later confirmed by a notable discontinuity in the intensity of the main (100) diffraction from the mesoporous silica observed through SAXS experiments, which is related to the change in the scattering contrast before and after the crystallization or melting of the polymer chains. Furthermore, the usual α modification of PHB was developed in all samples. Finally, a preliminary investigation of mechanical and relaxation parameters was carried out through dynamic-mechanical thermal analysis (DMTA). The results show, in the temperature interval analyzed, two relaxations, named α and ß (the latest related to the glass transition) in order of decreasing temperatures, in all specimens. The role of silica as a filler is mainly observed at temperatures higher than the glass transition. In such cases, stiffness is dependent on SBA-15 content.

Mechanical and Thermal Analysis of Duroplastic Matrix Composites over a Range of Temperatures.

It is commonly acknowledged that polymer composites in service are often subjected to not only intricate mechanical loads but also harsh environmental conditions. The mechanical and thermal properties of five particular composites are explored here. The composites are composed of laminates of glass cloth type "E" sheet infilled with a duroplastic matrix. This is a thermoset polymer-epoxy resin with different molecular weights. The composites were fabricated by IZOERG company, which is based in Poland. The final articles were 1.5 mm thick by 60 cm long and 30 cm wide, with the glass layers arranged parallel to the thickness. Young's modulus and tensile strength were measured at room temperature. Using the thermal analysis of dynamic mechanical properties (DMTA), the values of the storage modulus and the loss modulus were determined, and the damping factor was used to determine the glass transition temperature (Tg). It was revealed that the nature of changes in the storage modulus, loss modulus, and damping factor of composite materials depends on the type of epoxy resin used. Thermal expansion is a crucial parameter when choosing a material for application in cryogenic conditions. Thanks to the TMA method, thermal expansion coefficients for composite materials were determined. The results show that the highest value of the coefficient of thermal expansion leads the laminate EP_4_2 based on brominated epoxy resin cured with novolac P. Duroplastic composites were characterized at cryogenic temperatures, and the results are interesting for developing cryogenic applications, including electric motors, generators, magnets, and other devices.

Cheminformatics and artificial intelligence for accelerating agrochemical discovery.

The global cost-benefit analysis of pesticide use during the last 30 years has been characterized by a significant increase during the period from 1990 to 2007 followed by a decline. This observation can be attributed to several factors including, but not limited to, pest resistance, lack of novelty with respect to modes of action or classes of chemistry, and regulatory action. Due to current and projected increases of the global population, it is evident that the demand for food, and consequently, the usage of pesticides to improve yields will increase. Addressing these challenges and needs while promoting new crop protection agents through an increasingly stringent regulatory landscape requires the development and integration of infrastructures for innovative, cost- and time-effective discovery and development of novel and sustainable molecules. Significant advances in artificial intelligence (AI) and cheminformatics over the last two decades have improved the decision-making power of research scientists in the discovery of bioactive molecules. AI- and cheminformatics-driven molecule discovery offers the opportunity of moving experiments from the greenhouse to a virtual environment where thousands to billions of molecules can be investigated at a rapid pace, providing unbiased hypothesis for lead generation, optimization, and effective suggestions for compound synthesis and testing. To date, this is illustrated to a far lesser extent in the publicly available agrochemical research literature compared to drug discovery. In this review, we provide an overview of the crop protection discovery pipeline and how traditional, cheminformatics, and AI technologies can help to address the needs and challenges of agrochemical discovery towards rapidly developing novel and more sustainable products.

Analysis of Thermomechanical Properties and the Influence of Machining Process on the Surface Structure of Composites Manufactured from Metal Chips with a Polymer Matrix.

Nowadays, the dynamic development of the entire market of composite materials is noticeable, which is very often associated with the need to use waste or recycled materials in their production. In the process of producing composites themselves, the easy possibility of shaping their mechanical and thermomechanical properties becomes apparent, which can be a big problem for materials with a homogeneous structure. For the tests, samples made of a combination of acrylic-phenolic resin with fine aluminum and brass chips were used. The tests were performed for composite samples produced by pressing. This paper presents the results of the DMTA method of the conservative modulus and the tangent of mechanical loss angle of the composite, a detailed stereometric analysis of the surface after machining, roughness parameters and volumetric functional parameters were performed. For the tested samples, changes in the values of the conservative modulus and the mechanical loss coefficient were recorded, which indicated significant differences for the composite with brass chips in relation to composites with aluminum chips. In the case of the composite with aluminum chips, slight changes in the conservative modulus were recorded in the glass transition phase and the elastic deformation phase at different frequencies. In contrast, for composites with brass, slight changes were recorded in the entire range of the course of the conservative module as a function of temperature when different excitation frequencies were applied. In relation to the polymer matrix, a significant increase in the value of the conservative modulus of composites was recorded in the entire temperature range of the test. Significant differences were recorded in the study of the surface of composites in the case of using different materials obtained after machining as fillers. The dependences of the amplitude parameters of the surface after machining the sample made of phenolic-acrylic resin prove the poor performance properties of the surface. The use of chips in the composite significantly changed the surface geometry.

Influence of Carbon Micro- and Nano-Fillers on the Viscoelastic Properties of Polyethylene Terephthalate.

In this research study, three carbon fillers of varying dimensionality in the form of graphite (3D), graphite nano-platelets (2D), and multiwall carbon nanotubes (1D) were incorporated into a matrix of poly (ethylene terephthalate), forming carbon-reinforced polymer composites. Melt compounding was followed by compression moulding and then a quenching process for some of the samples to inhibit crystallization. The samples were analysed using dynamic mechanical thermal analysis (DMTA) and scanning electron microscopy (SEM), considering the dimensionality and loading of the carbon fillers. The dynamic mechanical analysis revealed a similar decline of storage moduli for all composites during the glassy to rubbery transition. However, storage moduli values at room temperature increased with higher loading of nano-fillers but only to a certain level; followed by a reduction attributed to the formation of agglomerates of nanotubes and/or rolled up of nano-platelets, as observed by SEM. Much greater reinforcement was observed for the carbon nanotubes compared to the graphite and or the graphite nano-platelets. The quenched PET samples showed significant changes in their dynamic mechanical properties due to both filler addition and to cold crystallization during the DMTA heating cycle. The magnitude of changes due to filler dimensionality was found to follow the order: 1D > 2D > 3D, this carbon filler with lower dimensionality have a more significant effect on the viscoelastic properties of polymer composite materials.

Transparent Polymer Blends of Poly(methyl methacrylate) and Poly(propylene glycol).

Polymer blends, obtained by polymerization of methyl methacrylate in the presence of poly(propylene glycol), are investigated. Poly(propylene glycol) acts as a plasticizer, significantly lowering poly(methyl methacrylate)'s glass transition temperature and decreasing its elasticity modulus and yield stress. The mixture of methyl methacrylate with poly(propylene glycol) is more stable than its mixture with currently used poly(ethylene glycol), which leads to more uniform distribution and higher possible content of the plasticizer. Unlike low molecular weight plasticizers, poly(propylene glycol) is less prone to migration and exudation during manufacturing process and in use, and has low toxicity. Dynamic mechanical thermal analysis, compression testing and X-ray diffraction were used to investigate how the properties of the material depend on the content and molecular weight of the poly(propylene glycol) in the polymer blend. It was shown that the dependence of the glass transition temperature of methyl methacrylate polymerized in the presence of poly(propylene glycol) on the molar fraction of propylene glycol units is linear, and poly(propylene glycol) with lower molecular weight affects properties of the material stronger than poly(propylene glycol) with higher molecular weight. Therefore, the addition of poly(propylene glycol) allows to control the properties of poly(methyl methacrylate) easily and within wide range.

Analysis of Thermomechanical Properties of Polyethylene with Cement Addition.

The paper undertakes preliminary research towards the identification of the use of plastic waste, taking into account the possibility of increasing their mechanical strength and reducing flammability, as well as reducing the emission of harmful compounds to the atmosphere through the addition of cement. This is extremely important not only from the point of view of the wide use of plastic products in the industry, but also their thermal utilization. The present study deals with the aspect of the utilization of waste polyethylene (HDPE) as a matrix in composites with filler in the form of cement at 5 and 10%. The composite samples were prepared by injection molding after the prior proper mixing of the components. Comparative thermomechanical (DSC, tensile strength, DMTA), microstructure and flammability results are presented for HDPE samples and their composites with cement. It was found that the addition of cement as a filler to polyethylene made it possible to obtain composites with good thermomechanical properties.

'Cookies on a tray': Superselective hierarchical microstructured poly(l-lactide) surface as a decoy for cells.

In this research we developed a micro-sized hierarchical structures on a poly(l-lactide) (PLLA) surface. The obtained structures consist of round-shaped protrusions with a diameter of ~20 µm, a height of ~3 µm, and the distance between them ~30 µm. We explored the effect of structuring PLLA to design a non-cytotoxic material with increased roughness to encourage cells to settle on the surface. The PLLA films were prepared using the casting melt extrusion technique and were modified using ultra-short pulse irradiation - a femtosecond laser operating at λ = 1030 nm. A hierarchical microstructure was obtained resembling 'cookies on a tray'. The cellular response of fibro- and osteoblasts cell lines was investigated. The conducted research has shown that the laser-modified surface is more conducive to cell adhesion and growth (compared to unmodified surface) to such an extent that allows the formation of highly-selectively patterns consisting of living cells. In contrast to eukaryotic cells, the pathogenic bacteria Staphylococcus aureus covered modified and unmodified structures in an even, non-preferential manner. In turn, adhesion pattern of eukaryotic fungus Saccharomyces boulardii resembled that of fibro- and osteoblast cells rather than that of Staphylococcus. The discovered effect can be used for fabrication of personalized and smart implants in regenerative medicine.

Comparative Analysis of Polyurethane Drive Belts with Different Cross-Section Using Thermomechanical Tests for Modeling the Hot Plate Welding Process.

The paper presents a comparative analysis of the circular and flat cross-section belts using measurements of a set of thermomechanical parameters, contributing to research about hot plate welding of drive belts. On the basis of thermogravimetric and spectrophotometric tests, information about the same chemical composition of the two belts was obtained. Dynamic thermomechanical analysis and scanning differential calorimetry provided information about a small difference between belts, which disappeared when the material was placed in a state of increased temperature and mechanical stress. On the basis of the analysis of the specific heat, thermal diffusion, density, and hardness, the values of the selected thermal properties of the belt were obtained, and a large similarity between the belts was identified. On the basis of the novel performed test cycle, it has been hypothesized that circular and flat belts made from thermoplastic polyurethane elastomer could be used interchangeably for butt-welding testing. It has also been proven that cyclic thermomechanical loads unify the properties of both materials so that multiple mechanical and thermal loads do not result in any change in the material properties of the two belts. As a consequence, changes in the weld properties after welding, compared to a solid belt, are not expected.

Dynamic mechanical and thermal properties of clear aligners after thermoforming and aging.

BACKGROUND: Based on the role of properties of aligner materials on their efficiency, we aimed to assess their thermomechanical properties after thermoforming and simulated aging. METHODS: In this experimental study, 96 samples of polyethylene terephthalate glycol (PETG) aligners (Duran and Erkodur) were prepared and divided to three groups: control (C), after thermoforming (T), after thermoforming and aging (TA). Thermoforming was done through 3D-printed molds, and aging was exerted by 200 thermal cycles after immersion in 37°C distilled water for 24h. Flexural modulus, hardness, glass transition temperature (Tg), elastic and viscous modulus, and loss factor were evaluated. Two-way ANOVA, T-independent, and Tukey HSD tests were done for statistical analysis and significance level was set to 0.05. RESULTS: In both materials, flexural modulus decreased significantly after thermoforming, 88% in Duran and 70% in Erkodur, but did not change significantly after aging. After thermoforming, hardness decreased significantly in both materials (22% in Duran and 7.6% in Erkodur). Dynamic Tg was significantly lower in T and TA in both materials. At all temperatures (25, 37, 55°C) in Duran, the elastic modulus difference was only significant between C and TA, but in Erkodur, it decreased significantly in T, and there was no significant change after aging. Viscous modulus and loss factor showed the same change patterns at all temperatures. In both materials, they increased after thermoforming, but did not change significantly after aging. CONCLUSION: Thermoforming had more prominent role than aging in diminishing of thermomechanical properties. In general, Duran had greater thermomechanical stability than Erkodur.

How dry is dry? Molecular mobility in relation to thallus water content in a lichen.

Lichens can withstand extreme desiccation to water contents of ≤ 0.1 g H2O g-1 DW, and in the desiccated state are among the most extremotolerant organisms known. Desiccation-tolerant life-forms such as seeds, mosses and lichens survive 'vitrification', that is the transition of their cytoplasm to a 'glassy' state, which causes metabolism to cease. However, our understanding of the mechanisms of desiccation tolerance is hindered by poor knowledge of what reactions occur in the desiccated state. Using Flavoparmelia caperata as a model lichen, we determined at what water contents vitrification occurred upon desiccation. Molecular mobility was assessed by dynamic mechanical thermal analysis, and the de- and re-epoxidation of the xanthophyll cycle pigments (measured by HPLC) was used as a proxy to assess enzyme activity. At 20 °C vitrification occurred between 0.12-0.08 g H2O g-1 DW and enzymes were active in a 'rubbery' state (0.17 g H2O g-1 DW) but not in a glassy state (0.03 g H2O g-1 DW). Therefore, desiccated tissues may appear to be 'dry' in the conventional sense, but subtle differences in water content will have substantial consequences on the types of (bio)chemical reactions that can occur, with downstream effects on longevity in the desiccated state.

Rheology of carbohydrate blends close to the glass transition: Temperature and water content dependence of the viscosity in relation to fragility and strength.

Several modifications of the Williams-Landel-Ferry (WLF) equation that incorporate the water-content dependence of the viscosity are introduced and applied to the fitting the zero-shear viscosity of a systematic series of maltopolymer-maltose blends for water contents w between 4% and 70% (M. Dupas-Langlet et al., Carbohydrate Polymers 213 (2019) 147-158). These models include a previously published model that addresses the water-content dependence of the viscosity via a Gordon-Taylor-type modification of the C2 coefficient of the WLF equation. New models that are based on two simple assumptions are introduced: 1. The viscosity at the glass transition temperature Tg decreases exponentially with the water content and 2. The WLF coefficient C2 depends linearly on the water content. The modified WLF models allow to extract the so-called isoviscosity lines, that connect points of varying temperature and water content that are characterized by the same viscosity. Based on data obtained between T = -15 °C and 70 °C using shear rheology (w = 30-70% w/w) and dynamic mechanical thermal analysis (w = 4-9% w/w), we conclude that the models provide a good fit of the experimental data, and that additional data, specifically very close to the glass transition line, is needed, to assess the hypotheses underlying the various modified WLF models. It is established that the viscosity at Tg is dependent on the composition and decreases with the content of maltose and water. The modified WLF models are used to determine Angell's fragility parameter m and Roos' strength parameter S. m and S are observed to increase, respectively decrease with increasing water and maltose content, signifying an increasing temperature dependence of the viscosity close to Tg with decreasing diluent content. The application of the isoviscosity concept to unit operations in the food and pharmaceutical industry is discussed. Specifically, we show how to analyze atomization, agglomeration, sintering and compaction using the isoviscosity concept.

verA Gene is Involved in the Step to Make the Xanthone Structure of Demethylsterigmatocystin in Aflatoxin Biosynthesis.

In the biosynthesis of aflatoxin, verA, ver-1, ordB, and hypA genes of the aflatoxin gene cluster are involved in the pathway from versicolorin A (VA) to demethylsterigmatocystin (DMST). We herein isolated each disruptant of these four genes to determine their functions in more detail. Disruptants of ver-1, ordB, and hypA genes commonly accumulated VA in their mycelia. In contrast, the verA gene disruptant accumulated a novel yellow fluorescent substance (which we named HAMA) in the mycelia as well as culture medium. Feeding HAMA to the other disruptants commonly caused the production of aflatoxins B1 (AFB1) and G1 (AFG1). These results indicate that HAMA pigment is a novel aflatoxin precursor which is involved at a certain step after those of ver-1, ordB, and hypA genes between VA and DMST. HAMA was found to be an unstable substance to easily convert to DMST and sterigmatin. A liquid chromatography-mass spectrometry (LC-MS) analysis showed that the molecular mass of HAMA was 374, and HAMA gave two close major peaks in the LC chromatogram in some LC conditions. We suggest that these peaks correspond to the two conformers of HAMA; one of them would be selectively bound on the substrate binding site of VerA enzyme and then converted to DMST. VerA enzyme may work as a key enzyme in the creation of the xanthone structure of DMST from HAMA.

Morphology Control in a Dual-Cure System for Potential Applications in Additive Manufacturing.

The polymerisation, morphology and mechanical properties of a two-component in-situ reacting system consisting of a rubbery dimethacrylate and a rigid epoxy polymer were investigated. The methacrylate component of the mixture was photocured using UV light exposure and, in a second curing process, the mixture was thermally postcured. The polymers formed a partially miscible system with two glass transition temperature (Tg) peaks measured using dynamic mechanical thermal analysis (DMTA). The composition and relative rate of reaction of the two orthogonal polymerisations influenced the extent of miscibility of the two polymer-rich phases and the samples were transparent, indicating that the two phases were finely dispersed. The addition of a glycidyl methacrylate compatibiliser further increased the miscibility of the two polymers. The utility of this polymer system for additive manufacturing was investigated and simulated through layer-by-layer processing of the mixture in two steps. Firstly, the methacrylate component was photocured to solidify the material into its final shape, whilst the second step of thermal curing was used to polymerise the epoxy component. With the use of a simulated photomask, a simple shape was formed using the two orthogonal polymerisation stages to produce a solid object. The mechanical properties of this two-phase system were superior to a control sample made only of the methacrylate component, indicating that some reinforcing due to polymerisation of the epoxy across the interfaces had occurred in the postcuring stage.

Influence of blend ratio and water content on the rheology and fragility of maltopolymer/maltose blends.

The rheological behavior of blends of a fractionated maltopolymer (Mw = 1.4⋅104 Da) and the disaccharide maltose is investigated as a function of water content and temperature, with emphasis on the viscosity and molecular relaxations in the approach to the glass transition. Shear rheology is combined with dynamic mechanical thermal analysis to probe viscosities between 1 mPa s and 1012 Pa s. Differential scanning calorimetry is used to determine glass transition and enthalpy relaxation of the carbohydrate blends. The rheology data are fitted with a modified version of Williams-Landel-Ferry equation (Williams et al., 1955). The fragility of the blends is quantified using Angell's fragility parameters m and F1/2 (Angell, 1991) and Roos' strength parameter S (Roos, 1995b). The increase in fragility of the maltopolymer systems with increasing water and maltose contents is interpreted as a reduction of the entanglement density and an interference of water molecules with the hydrogen bonding between the carbohydrate chains.

Dental microwear textural analysis as an analytical tool to depict individual traits and reconstruct the diet of a primate.

OBJECTIVES: Dental microwear is a promising tool to reconstruct animals' diet because it reflects the interplay between the enamel surface and the food items recently consumed. This study examines the sources of inter-individual variations in dietary habits in a free-ranging population of mandrills (Mandrillus sphinx) using a combination of feeding monitoring and in vivo dental microwear textural analysis (DMTA). METHODS: We investigated the impact of seasonality and individual traits on four DMTA parameters. In parallel, we further studied the influence of the physical properties of the food items consumed on these four parameters, using three proxies (mechanical properties, estimates of phytolith and external grit contents). RESULTS: We found that seasonality, age, and sex all impact DMTA parameters but those results differ depending on the facet analyzed (crushing vs. shearing facets). Three DMTA parameters (anisotropy, complexity, and heterogeneity of complexity) appear sensitive to seasonal variations and anisotropy also differs between the sexes while textural fill volume tends to vary with age. Moreover, the physical properties of the food items consumed vary seasonally and also differ depending on individual sex and age. CONCLUSION: Considering the interplay between the tested variables and both dental microwear and diet, we reaffirm that food physical properties play a major role in microwear variations. These results suggest that DMTA parameters may provide valuable hints for paleoecological reconstruction using fragmentary fossil dental remains.

A comparative study on the effects of ultrathin luminescent graphene oxide quantum dot (GOQD) and graphene oxide (GO) nanosheets on the interfacial interactions and mechanical properties of an epoxy composite.

The reinforcement effect of graphene oxide nanosheets on the mechanical properties of an epoxy coating has been extensively studied. However, the effect of graphene oxide quantum dot (GOQD) as a new unique carbon based nanomaterial (with lateral dimension of 5-6nm and thickness of one carbon atom) on the mechanical properties of epoxy coating has not been reported and compared with GO yet. So this study aims at fabrication of a high-performance polymer composite with unique mechanical properties using GOQD nanosheets. GO and GOQD were obtained through two different strategies of "top-down" synthesis from an expandable graphite by a modified Hummers' method and an easy "bottom-up" method by carbonizing citric acid, respectively. The morphology, size distribution, microstructure and chemistry of the GO and GOQD were compared by utilizing X-ray diffraction (XRD) analysis, atomic force microscopy (AFM), high resolution-transmission electron microscopy (HR-TEM), high resolution field-emission scanning electron microscopy (FE-SEM), thermal gravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS). Results obtained from these analyses confirmed successful synthesize of GOQD and GO nanosheets. The reinforcement effect of GO and GOQD nanosheets on the mechanical properties of the epoxy coating was studied by dynamic mechanical thermal analysis (DMTA) and tensile test. It was found that the GOQD could remarkably enhance the energy of break, Young's modulus, tensile stress and interfacial interactions compared to the neat epoxy and the one reinforced with GO nanosheets. GOQD improved the fracture toughness by factor of 175% and 700% compared to the GO/Epoxy and neat epoxy, respectively.

A novel fabrication of a high performance SiO(2)-graphene oxide (GO) nanohybrids: Characterization of thermal properties of epoxy nanocomposites filled with SiO(2)-GO nanohybrids.

In this study it has been aimed to enhance the thermal resistance of epoxy coating through incorporation of SiO2-GO nanohybrids. SiO2-GO nanohybrids were synthesized through one-step sol-gel route using a mixture of Tetraethylorthosilane (TEOS) and 3-Aminopropyl triethoxysilane (APTES) silanes. The SiO2-GO nanohybrids were prepared at various hydrolysis times of 24, 48 and 72h. Then 0.2wt.% of GO and SiO2-GO nanohybrids were separately incorporated into the epoxy coating. Results revealed that amino functionalized SiO2 nanoparticles with particle size around 20-30nm successfully synthesized on the basal plane of GO. Results showed significant improvement of dispersion and interfacial interactions between nanohybrids and epoxy composite arising from covalent bonding between the SiO2-GO and the epoxy matrix. It was found that the thermal resistance of SiO2-GO nanohybrids and SiO2-GO/Epoxy nanocomposite was noticeably higher than GO and epoxy matrix, respectively.

Effect of sugar addition on glass transition temperatures of cassava starch with low to intermediate moisture contents.

This work studies how sucrose (S) addition modifies the thermal properties of cassava starch (CS). Neat CS and CS-S blends with 4, 6 and 8% sugar contents (CS-S-4%, CS-S-6% and CS-S-8%) were prepared and analyzed by differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA), in a wide range of moisture levels (2-20%). In equilibrated samples with moisture contents lower than 10%, twoendothermic steps were observed during first DSC heating scans and two corresponding relaxation maxima in tan δ were detected by DMTA. The first transition, detected at around 45-55°C by both DSC and DMTA, is frequently found in starchy foods, while the second observed at higher temperatures is associated to the glass transition temperature of the blends. At higher moisture contents, only one thermal transition was observed. Samples analyzed immediately after cooling from the melt (i.e., after erasing their thermal history), exhibited a single glass transition temperature, regardless of their moisture content. Addition of sugar promotes water plasticization of CS only at high moisture contents. In the low moisture content range, anti-plasticization was observed for both neat and sugar-added CS samples. Addition of sugar decreases the moisture content needed to achieve the maximum value of the glass transition temperature before plasticization starts. The results of this work may be valuable for the study of texture establishment in low moisture content extruded food products.

Electromagnetic and Dynamic Mechanical Properties of Epoxy and Vinylester-Based Composites Filled with Graphene Nanoplatelets.

Development of epoxy or epoxy-based vinyl ester composites with improved mechanical and electromagnetic properties, filled with carbon-based nanomaterials, is of crucial interest for use in aerospace applications as radar absorbing materials at radio frequency. Numerous studies have highlighted the fact that the effective functional properties of this class of polymer composites are strongly dependent on the production process, which affects the dispersion of the nanofiller in the polymer matrix and the formation of micro-sized aggregations, degrading the final properties of the composite. The assessment of the presence of nanofiller aggregation in a composite through microscopy investigations is quite inefficient in the case of large scale applications, and in general provides local information about the aggregation state of the nanofiller rather than an effective representation of the degradation of the functional properties of the composite due to the presence of the aggregates. In this paper, we investigate the mechanical, electrical, and electromagnetic properties of thermosetting polymer composites filled with graphene nanoplatelets (GNPs). Moreover, we propose a novel approach based on measurements of the dielectric permittivity of the composite in the 8⁻12 GHz range in order to assess the presence of nanofiller aggregates and to estimate their average size and dimensions.