Differential Scanning Calorimetry Results Research Articles

Paper‐based sensors for real‐time cure monitoring in the production of glass fiber‐reinforced phenol‐formaldehyde composites for aerospace interiors

AbstractThe aerospace industries demand for advanced materials necessitates stringent quality control measures, particularly for composite structures to ensure optimal curing and structural integrity. Traditional methods like differential scanning calorimetry (DSC) and dynamic mechanical analysis, while useful, are limited to laboratory settings. This study explores the use of a printed paper‐based sensor for real‐time cure monitoring of glass fiber‐reinforced phenol‐formaldehyde (PF/GF) prepregs. The sensor, composed of a cellulose paper substrate with screen‐printed electrodes, offers flexibility, ease of integration, and cost‐effectiveness compared to commercial polymer‐based dielectric sensors. Real‐time monitoring with the printed paper‐based sensor was conducted at temperatures ranging from 130 to 180°C, both with and without pressure, and validated against DSC and Fourier‐transform infrared (FTIR) spectroscopy. The results showed a strong correlation between real‐time monitoring and the DSC prediction model, as well as FTIR spectroscopy. Notably, the real‐time monitoring revealed a shorter curing cycle on the production line than the predicted cure kinetic model, which is crucial for large‐scale production, such as fabricating honeycomb panels for aircraft interiors. This research underscores the importance of innovative sensor technologies in improving quality control and manufacturing efficiency in aerospace composites.Highlights Cure Monitoring of PF‐based prepregs was carried out using paper‐based sensor. Sensor offered reproducibility and seamless integration in composites. Sensor data showed a strong correlation with DSC and FTIR spectroscopy results. Paper sensors enable online monitoring of composite in aerospace manufacturing.

Insight into in situ enzymatic transesterification modification of polyethylene terephthalate fibers with polyethylene glycol

Polyethylene terephthalate (PET) fabric was enzymatically modified with polyethylene glycol (PEG). Lipase from Aspergillus oryzae was used as a catalyst. The wetting behavior of the modified PET fabric was characterized by the water contact angle, water adsorption dynamics and moisture regain. The initial water contact angle of the modified fabric decreased from 129.3° to 74.9°. The water absorption dynamics results indicated that the equilibrium water absorption amount of the modified fabric was approximately 10 times greater than that of the untreated sample. The initial absorption rate (Vinit) of the modified fabric was almost 30 times higher than that of the untreated fabric. The moisture regain reached 3.52% after modification. Scanning electron microscopy revealed granular and sheet coatings on the surface of the modified fabric. Chemical linkage of PEG onto the PET fibers was confirmed by attenuated total reflection–Fourier transform infrared spectroscopy. The modification had no significant effect on the thermal properties of the PET fabrics according to the thermogravimetric curve and differential scanning calorimetry results. The mechanical properties of the modified fabric were slightly improved. Therefore, in situ enzymatic transesterification between PET and PEG could be a potential novel modification approach for adding value to PET fiber textiles.

Effects of microwave treatment on structural and functional properties of germinated corn starch.

Measuring the germination index of corn, and gelatinization index, thermodynamic properties, long-range structure, short-range structure and particle morphology of corn starch, the study aimed to investigate the effects of different microwave (MW) treatment on the structural and functional properties of germinated corn starch. The results indicated that after appropriate MW treatment, the germination indices (germination rate, germination potential, sprout length and sprout weight) of germinated corn starch were improved after 7 days of germination. In addition, MW treatment also affected the structure of germinated corn starch. MW treatment could reduce the relative crystallinity of starch, but did not change the crystal type and the peak position of each absorption peak in Fourier transform infrared spectra. In addition, rapid visco-analysis and differential scanning calorimetry results showed, respectively, that MW treatment decreased the peak viscosity of germinated corn starch and increased the gelatinization temperature. Finally, MW treatment made the starch surface become rough, destroyed the starch particle structure and produced random cracks and voids. Overall, the present study proves that appropriate MW treatment is an effective measure for the modification of germinated corn starch, and provides a theoretical basis for the application of MW technology in germinated corn products. © 2024 Society of Chemical Industry.

Diacerein-loaded surface modified iron oxide microparticles (SMIOMPs): an emerging magnetic system for management of osteoarthritis via intra-articular injection

IntroductionOsteoarthritis (OA) is regarded as one of the most prevealent irreversible joint degenerative disorder worldwide. Recently, considerable interest in utilizing intra-articular (IA) injections for managing OA has been raised.MethodsIn this study, IA injectable surface modified iron oxide microparticles (SMIOMPs) loaded with Diacerein (DCN) were developed. The effects of formulation parameters on particle size, entrapment efficiency, and zeta potential were explored using factorial design. The optimized formulation was characterized regarding morphology and in vitro release. Differential scanning calorimetry (DSC) and Fourier-transform infrared spectroscopy (FTIR) were done to assess interactions. Further, sterilization and in vivo performance in rats with induced arthritis has been performed for the optimized formulation.Results and DiscussionThe selected optimized system included 2M FeCL3 and 1% chitosan as a surface modifier achieved high drug entrapment of 85.25% with a PS of 1.54 µm and sustained DCN release. Morphological examination of the optimized formulation revealed spherical particles with chitosan coat. DSC and FTIR results indicated the absence of undesired interactions between DCN and the used components. No significant change in the measured parameters was observed following sterilization using gamma radiation. In vivo assessment revealed superior performance for the optimized formulation in reducing cartilage inflammation and degradation. Plasma levels of tumor necrosis factor α and Interleukin-1 beta, as well as knee diameter, were significantly reduced in the treated groups compared to the untreated ones.ConclusionOverall, the results suggest that the proposed DCN-loaded SMIOMPs represent a promising advancement in the arena of cartilage regeneration.

Initial evaluation of waste phosphogypsum for its use as a precursor for bioceramic materials

In this study, the phosphogypsum waste taken from various places in the factory dump located in Kėdainiai (Lithuania) was reinspected and characterised by different physico-chemical characterisation methods. The results of X-ray diffraction analysis, thermogravimetric analysis and differential scanning calorimetry, Fourier transform infrared spectroscopy, energy-dispersive X-ray analysis, elemental analysis using inductively coupled plasma optical emission and X-ray fluorescence spectroscopy confirmed that the main crystalline phase of the phosphogypsum waste is gypsum (CaSO4·2H2O). The surface morphology of the investigated materials was analysed using scanning electron microscopy. The specific surface area was determined by the Brunauer–Emmet–Teller method. The pore size distribution of the material produced was obtained using the Barrett–Joyner–Halenda method. This study also demonstrated that the phosphogypsum waste could be successfully used as a precursor for the dissolution-precipitation synthesis of high quality bioceramic calcium hydroxyapatite.

Characterization of extracted alpha cellulose from Manihot esculenta (cassava) peels as formulation aid for paracetamol tablet

Background: Alpha-cellulose as a pharmaceutical excipient can be employed as a binding agent in tablet formulation. Cassava peels husk are waste agricultural material and is being investigated for its α-cellulose for use in oral solid pharmaceutical formulation. Purpose: The objective of this study is to extract α-cellulose from cassava peels agro-industrial waste using a standard method, subject the extracted cassava peels cellulose and determine its phytochemical and physicochemical properties of formulated granules of paracetamol. Methods: Alpha-cellulose from cassava peel was extracted using alkali method. The fresh peels were prepared, milled into slurry and de-watered to obtain a coarse wet material, dried, milled and sieved to obtain very fine powdered particles. Phytochemical analysis and characterization of extracted α-cellulose powder were determined. Differential scanning calorimetry (DSC), scanning electron micrographs (SEM), and x-ray diffractogram (XRD) analysis of extracted cassava peel cellulose were done. Paracetamol granules was prepared by wet granulation using varying concentrations of the binders. Results: DSC and XRD results revealed a semi-crystalline material with amorphous and crystalline regions. while the SEM showed a lumpy structure and reticular shape. Pre-compression evaluations of the formulated batches of paracetamol granules showed that cassava peels cellulose (CPC) have similar flow properties with those of microcrystalline cellulose BP (MCC) and acacia BP (ACA) powders respectively. The granules have free flow properties with average angles of repose (CPC ≤ 27.60 MCC < 26.90 and ACA ≤ 25.60), compressibility index (CPC ≤ 25, MCC ≤ 23 and ACA ≤ 21.7%), Hausner’s ratio (CPC ≤ 1.32, MCC ≤ 1.31, and ACA ≤ 1.27) respectively. Conclusion: The extracted cassava peel α-cellulose was found ideal as pharmaceutical excipient binder in oral solid dosage forms.

ESTUDIO DE LA RESPUESTA I-V EN CELDAS DE MEMORIA DESb70Te30

Chalcogenide glasses are within the group of phase change materials and are promising in their application to non-volatile electronic memories. Under electrical pulses, they can circulate between two amorphous and crystalline structural states that are well differentiated in their conductivity. Assuming that the phase change mechanisms depend on the energy per unit volume delivered to the sensitive material, it is desirable to build cells on a micrometer scale, also considering that they could eventually be integrated into microelectronic manufacturing processes. In a previous work, we observed an abrupt decrease in the resistance of Sb70Te30base thin films deposited by laser ablation in a temperature range of approximately 445 K when the sample is heated at low rates. From the results of differential scanning calorimetry and X-ray diffraction on samples obtained by the same method, we associate the change in resistivity with the crystallization process. In this work, we build micrometric devices with rectangular surface with Sb70Te30assensitive material, deposited on coplanar electrodes with spacing L (8 and 16μm) and width W (4, 8, 16, 32 and 64μm). We measure the voltage response of the devices when excited by scanning of increasing current and, between consecutive scanning, we measure the remaining resistance by applying a constant voltage value. In curves I-V, we identify a transformation from the original state to one of lower resistance, attributable to crystallization, but it was not possible to perform the reverse transformation to a state of higher resistance. Starting from the lack of knowledge about the conductivity of the material, we simulate the electric field in the cell using the Finite Element Method. The electrical conductivity of the chalcogenide glass in its initial state (amorphous) was estimated by adjusting its value in the simulations with different geometries, minimizing the difference between the measured and simulated resistances.

The physicomechanical optimization and antimicrobial properties of the Ɛ-polylysine/ZnO nanoparticles loaded active packaging films

Response surface methodology (RSM) was used to evaluation the effects of Ɛ-polylysine (Ɛ-PL: 0–5 wt%) and zinc oxide nanoparticle (ZnO: 0–5 wt%) on the physico-mechanical properties of the gelatin/polyvinyl alcohol (G/PVA) based nanocomposite packaging films. Using Design-Expert 7.0.0 software, numerical and graphical improvements were also carried out. The optimization was focused on increasing the values of the ultimate tensile strength (UTS), strain at break (SAB), Young's modulus (YM), and lightness (L), and reducing the values of the water vapor permeability (WVP), yellowness index (YI), and overall color difference (∆E). The overall optimal concentrations of ZnO and Ɛ-PL were 1.00 (wt%) and 4.30 (wt%), respectively, with a maximum desirability of 75 %. Additionally, the microstructure, surface topography, interactions, and distribution quality of ZnO nanoparticles and Ɛ-PL in the biopolymer matrix were analyzed using Scanning Electron Microscopy, Atomic Force Microscopy, Fourier Transform Infrared Spectroscopy, and X-ray diffraction measurements. The result of differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) confirmed improved thermal stability of nanocomposite films containing ZnO nanoparticles and Ɛ-PL. MIC test showed that ZnO and Ɛ-PL were effective against E. coli, S. aureus, P. fluorescence, and S. typhimurium at the concentration of 2–3 and 10–12 mg/mL, respectively. The antimicrobial activity of G/PVA nanocomposites containing ZnO, Ɛ-PL, and ZnO/Ɛ-PL against E. coli was more than S. aureus.

DNA interaction of selected tetrahydropyrimidine and its effects against CCl4-induced hepatotoxicity in vivo: Part II.

Tetrahydropyrimidine (compound A = methyl 4-[4'-(heptyloxy)-3'-methoxyphenyl]-1,6-dimethyl-2-thioxo-1,2,3,4-tetrahydropyrimidine-5-carboxylate) was chosen for in vivo studies after exhibiting noteworthy in vitro activity against the K562 and MDA-MB-231 cell lines, with IC50 values of 9.20 ± 0.14 µM and 12.76 ± 1.93 µM, respectively. According to experimental (fluorescence titration, viscosity, and differential scanning calorimetry) results, A interacts with DNA via the minor groove. In vivo, acute oral toxicity studies in Wistar albino rats proved no noticeable symptoms of either toxicity or death during the follow-up period. Genotoxic and antigenotoxic studies at three different concentrations of A (5, 10, and 20 mg/kg of body weight) in Wistar albino rats showed that the dose of 5 mg/kg body weight did not cause DNA damage and had a remarkable DNA protective activity against CCl4-induced DNA damage, with a percentage reduction of 78.7%. It is also important to note that, under the investigated concentrations of A, liver damage is not observed. Considering all experimental outcomes realized under various in vivo investigations (acute oral toxicity, genotoxicity, antigenotoxicity, and biochemical tests), compound A could be a promising candidate for further clinical testing.

Optimization of FFF process parameters to improve the tensile strength and impact energy of polylactic acid/carbon nanotube composite

AbstractIn this study, the process parameters of fused filament fabrication are optimized to improve the tensile strength and impact energy of polylactic acid/carbon nanotube (PLA/CNT) composite. Hence, the utility function (UF) technique and response surface method (RSM) are applied to explore the optimal levels of the effective parameters of print speed, nozzle temperature, and CNT content. The differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and SEM analyses are employed to examine the thermal properties of the printed samples. The results of DSC and TGA analyses exhibited that the incorporation of CNT into PLA enhanced the thermal strength of PLA/CNT composite. The addition of CNTs in the composite improved the tensile strength by 37%, while the addition of CNTs up to 4 wt% improved the impact energy by 29%. Moreover, an increment of the print speed to 60 mm/s reduced the impact energy (12%) and tensile strength (22%), while an increment of the nozzle temperature to 200°C enhanced the impact energy (9%) and tensile strength (12%). The optimization results demonstrated that the strength and impact energy of PLA/CNT composite optimized at CNT content of 2.8 wt%, print speed of 20 mm/s, and nozzle temperature of 209°C. Additionally, the impact energy and tensile strength of the PLA/CNT composite enhanced up to 62.5 MPa and 2.14 J at the optimum conditions.Highlights Application of FFF process for producing the PLA/CNT composite Investigating the impact of FFF parameters on the mechanical properties Estimating the optimal conditions of the FFF process

Enhancing the dyeability of polyurethane fibers by introducing protonated tertiary amine groups

Traditional polyurethane fibers (CPUF) are widely used in the preparation of blend clothing in order to improve the elasticity and comfort of fabrics. However, there has been a problem of low acid dye adsorption for CPUF, resulting in light hue of dyed CPUF. In this work, a poly (HMDI-BHOPA) was prepared with dicyclohexylmethane 4,4′-diisocyanate (HMDI) and 1,4-(2-hydroxyethyl) piperazine (BHOPA), and then added into the CPUF spinning solution for the preparation of modified polyurethane fibers (BPUFs) through dry-spinning technology. Tertiary amine groups were introduced after the addition of poly (HMDI-BHOPA), which could be protonated at acidic conditions to form binding sites for acid dyes, further enhancing the adsorption capacity of the fibers. Nuclear magnetic resonance spectroscopy (1H and 13C NMR) was used to confirm the structure of poly (HMDI-BHOPA). The results of differential scanning calorimetry (DSC) and thermogravimetry analysis (TGA) demonstrated that the addition of poly (HMDI-BHOPA) had little effect on the glass transition temperature and thermal stability of BPUFs. The addition of poly (HMDI-BHOPA) affected the ordered arrangement of hard segments and reduced crystallization enthalpy of hard and soft segments in polyurethane. Hence, the elastic recovery of BPUFs showed little change, and the elongation at break and break strength decreased compared to CPUF. Zeta potential testing results showed that BPUFs was protonated under acidic conditions. Dyeing results proved the enhancement of dyeability of BPUFs. The dyeing kinetics and thermodynamics of acid dyes on BPUFs were studied to investigate the dyeing mechanism. From the dyeing kinetics results, both CPUF and BPUFs fitted Elovich model. From dyeing thermodynamics results, Langmuir model showed a better applicability for BPUFs at a low pH and temperature condition, while Freundlich model fitted better for CPUF.

Novel differential scanning calorimetry (DSC) application to select polyhydroxyalkanoate (PHA) producers correlating 3-hydroxyhexanoate (3-HHx) monomer with melting enthalpy.

Polyhydroxyalkanoate (PHA) is an environmental alternative to petroleum-based plastics because of its biodegradability. The polymer properties of PHA have been improved by the incorporation of different monomers. Traditionally, the monomer composition of PHA has been analyzed using gas chromatography (GC) and nuclear magnetic resonance (NMR), providing accurate monomer composition. However, sequential analysis of the thermal properties of PHA using differential scanning calorimetry (DSC) remains necessary, providing crucial insights into its thermal characteristics. To shorten the monomer composition and thermal property analysis, we directly applied DSC to the analysis of the obtained PHA film and observed a high correlation (r2 = 0.98) between melting enthalpy and the 3-hydroxyhexanoate (3-HHx) mole fraction in the polymer. A higher 3-HHx fraction resulted in a lower melting enthalpy as 3-HHx provided the polymer with higher flexibility. Based on this, we selected the poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (P(3HB-co-3HHx)) producing strain from Cupriavidus strains that newly screened and transformed with vectors containing P(3HB-co-3HHx) biosynthetic genes, achieving an average error rate below 1.8% between GC and DSC results. Cupriavidus sp. BK2 showed a high 3-HHx mole fraction, up to 10.38mol%, with Tm(℃) = 171.5 and ΔH of Tm (J/g) = 48.0, simultaneously detected via DSC. This study is an example of the expansion of DSC for PHA analysis from polymer science to microbial engineering.

Experimental investigation on the thermal characteristics of Kevlar/hemp intraply hybrid composites: Influence of various weaving designs

In this work, several weaving designs of intra-ply woven fabric Kevlar/hemp fiber (KHE) reinforced epoxy hybrid composites are developed and their thermal characteristics are examined. Thermogravimetric analysis showed that intra-ply hybrid of plain and basket weave designs possessed highest thermal stability. The different weaving patterns of KHE hybrid composites have no effect on the glass transmission temperature (Tg) value as inferred from the differential scanning calorimetry results. The thermomechanical analysis clearly demonstrates the superior dimension stability of the hybrid composites with basket weave. Dynamic mechanical analysis reveals that twill weave KHE have exhibited the maximum storage modulus (2021 MPa), loss modulus (210 MPa) and lower tan delta (0.3090) values compared to all other composites. Based on the obtained results, it is denoted that all the fabricated KHE hybrid composites displayed improved thermal performance. It may be suitable for applications in thermal insulation panels, fire-resistant clothing, and automotive underbody shields.

Effect of extrusion using plasma-activated water on the structural, physicochemical, antioxidant and in vitro digestive properties of yam flour

The synergistic effects of plasma-activated water (PAW) and twin-screw extrusion (TSE) on the structural, physicochemical, antioxidant, and digestive properties of yam flour (YF) were studied. Compared to common TSE, PAW-TSE reduced the protein, starch, and polyphenol contents, swelling power, and gel property of YF, while PAW-TSE enhanced the flavonoid content, whiteness index, solubility, and antioxidant property of YF. Moreover, the results of structural characterization and differential scanning calorimetry indicated that the long-range or short-range ordering, and gelatinization enthalpy of starch in YF were reduced after PAW-TSE, while the structure ordering of proteins in YF increased. Furthermore, the in vitro digestibility results demonstrated a reduction in the rate of enzymatic hydrolysis, coupled with an increase in total contents of slowly digestible and resistant starch after PAW-TSE. It should be noted that TSE using PAW prepared by a longer plasma treatment resulted in a more significant improvement effect on YF.

Influence of Processing Parameters on Mechanical Properties and Degree of Crystallization of Polylactide.

This work attempts to assess the influence of process parameters on the change of mechanical properties and the degree of crystallinity of polylactide (PLA). PLA is a biodegradable material that has been widely used in various areas-from packaging, through medicine, to 3D printing, where it is used to produce prototypes. The method of processing is important, because the technological process and its parameters have a significant impact on the quality of the finished product. Their appropriate selection depends on quality and mechanical properties. The process parameters have an impact on the structure of PLA, specifically on the share of the crystalline phase, which is also important from the point of view of the functional properties of the finished product. This work assessed the impact of the technological parameters of the injection process on the final properties of the obtained samples. The obtained results of static tensile strength, hardness and differential scanning calorimetry (DSC) analysis confirm that changing these parameters affects the material properties.

Novel kraft-lignin-based adhesives for the production of particleboards

Lignin is produced worldwide in pulp mills and is currently mainly used for energy recovery. Because of its chemical properties, one possible utilisation is the production of lignin-based materials. Currently, developed lignin-based adhesives are based mainly on lignosulfonate instead of kraft lignin since lignosulfonate is more reactive than kraft lignin. However, worldwide substantially more kraft lignin is produced. The presented research deals with the development of resin chemically modified with kraft lignin up to 40% (w/w) content of kraft lignin. The synthesis of adhesives is described, and developed adhesives are characterised. Namely, viscosity, mechanical properties of resins and results of differential scanning calorimetry are presented. Furthermore, the developed kraft-lignin-based adhesives were used for the production of particleboards. Pre-pressing in a cold press followed by hot pressing in a laboratory press was used for the production of particleboards. The physical (thickness swelling, moisture uptake, vertical density profile), as well as mechanical (internal bonding, modulus of rupture, modulus of elasticity in three-point bending) properties of particleboards, were evaluated. The results clearly show that kraft lignin can be used for the production of lignin-based adhesives for the production of particleboards.

Euglena gracilis Protein: Effects of Different Acidic and Alkaline Environments on Structural Characteristics and Functional Properties.

Due to the growing demand for human-edible protein sources, microalgae are recognized as an economically viable alternative source of proteins. The investigation into the structural characteristics and functional properties of microalgin is highly significant for its potential application in the food industry as an alternative source of protein. In this research, we extracted protein from Euglena gracilis by using alkaline extraction and acid precipitation and investigated its structural characteristics and functional properties in different acidic and alkaline environments. The molecular weight distribution of Euglena gracilis protein (EGP), as revealed by the size exclusion chromatography results, ranges from 152 to 5.7 kDa. EGP was found to be rich in hydrophobic amino acids and essential amino acids. Fourier infrared analysis revealed that EGP exhibited higher α-helix structure content and lower β-sheet structure content in alkaline environments compared with acidic ones. EGP exhibited higher foaming properties, emulsifying activity index, solubility, free sulfhydryl, and total sulfhydryl in pH environments far from its isoelectric point, and lower fluorescence intensity (2325 A.U.), lower surface hydrophobicity, larger average particle size (25.13 µm), higher emulsifying stability index, and water-holding capacity in pH environments near its isoelectric point. In addition, X-ray diffraction (XRD) patterns indicated that different acidic and alkaline environments lead to reductions in the crystal size and crystallinity of EGP. EGP exhibited high denaturation temperature (Td; 99.32 °C) and high enthalpy (ΔH; 146.33 J/g) at pH 11.0, as shown by the differential scanning calorimetry (DSC) results. The findings from our studies on EGP in different acidic and alkaline environments provide a data basis for its potential commercial utilization as a food ingredient in products such as emulsions, gels, and foams.

Glycidyl methacrylate co-polymer emulsion-based heat and water-resistant wood adhesive

This work aims to add an epoxy-ended co-monomer to polyvinyl acetate (PVAc) emulsion adhesive-based wood adhesive to improve its resistance to heat and moisture. Here, glycidyl methacrylate (GMA), vinyl neodecanoate (VeoVa), and vinyl acetate (VAc) emulsion copolymers have been created and evaluated as wood adhesives. To prepare the emulsion-based adhesive samples, a polyvinyl alcohol (PVA) solution, aluminium chloride solution, preservatives, and a plasticizer are added. Following that, the poly(VAc–VeoVa–GMA) based adhesive sample is compared with the VAc, VeoVa, and methyl methacrylate (MMA) (poly(VAc-VeoVa-MMA)) co-polymer-based adhesive. Tensile shear strength of wood joints under dry and wet conditions was tested in compliance with EN 204-205 standard to assess the adhesives’ performance. The EN 14257 standard, which defines the shear stress of wood joints at 80 °C, was used to assess the heat resistance of the wood adhesives. Tests on the hardness of films confirmed the results of differential scanning calorimetry, which indicated that the glass transition temperature in the GMA-based adhesive was significantly higher than in the MMA-based adhesive. After 6 h of bonding, EN 204 shows that the tensile shear strength of a GMA-based adhesive increased by 15.56% in a dry environment, by 16.67% in a wet environment and 37.84% heat resistance when compared to a co-polymer-based adhesive based on MMA. The approach that was developed provides a simple and useful way of developing adhesives with enhanced heat, water, and bonding strength resistance.

Calorimetric and Raman spectroscopic studies of zwitterionic and anionic membrane interactions of phenolic compound coumarin

It is well known that polyphenols possess potent antioxidant qualities. However, the precise antioxidant action mechanism of phenolic compounds is still not well defined. It is evident that understanding the molecular mechanisms behind polyphenol-lipid interactions is necessary to comprehend this impact. The objective of this work is to examine the effect of phenolic compound coumarin on the physicochemical properties of cell membrane models. To accomplish this goal, model membranes made up of zwitterionic dimyristoylphosphatidylcholine (DMPC) and anionic dimyristoylphosphatidylglycerol (DMPG) lipids were used. These lipid species are the main component of the mammalian and gram-positive bacteria membranes, respectively. Differential scanning calorimetry (DSC) and Raman spectroscopy were applied for studying the interaction of coumarin with DMPC and DMPG. From the DSC results, it was found that pretransition was abolished for both lipid systems at 20 mol% coumarin. Main phase transition shifted to lower temperatures and broadened, but there was not a complete disappearance of main transition and coumarin was not fully miscible. A sharp peak at a higher temperature and a broad shoulder at a lower temperature of the main transition of DMPC were detected when compared to coumarin/DMPG binary system. A reduction in calorimetric enthalpy and entropy values of coumarin/DMPC system at 20 mol% was observed whereas an increase in these calorimetric parameters for coumarin/DMPG system occurred. Thus, the disorder was caused when 20 mol% coumarin interacts with DMPC lipid bilayers. The increase in enthalpy could be a result of the 20 mol% coumarin interactions with DMPG lipid bilayers or a possible generated partial interdigitation. From the Raman results, the peak height Raman intensity ratio I1090/I1130 showed that coumarin induces disorder in the DMPG bilayers in the gel phase due to the increasing gauche:trans ratio. According to the results obtained by DSC and Raman spectroscopy, it was found that coumarin has a varied effect on membranes made from lipids with choline and glycerol head groups. Thus, it is obvious that the polyphenol/membrane interactions can be significantly impacted by the lipids’ structural variations.

Eutectic mixtures containing the active pharmaceutical ingredient ezetimibe: Phase diagrams, solid state characterization and dissolution profiles

Cardiovascular disease represents the leading cause of death worldwide, according to the World Health Organization (WHO) report. One of the treatment strategies is the use of the drug ezetimibe (EZT). This drug is a cholesterol absorption inhibitor with low aqueous solubility, which affects its therapeutic efficacy. The purpose of this paper was to obtain eutectic materials of EZT with methylparaben (MPB), salicylic acid (SCA) and nicotinamide (NTM) coformers, and to study their phase diagrams, dissolution properties and hygroscopicity to assess possible enhancements. Phase and Tamman diagrams were constructed using differential scanning calorimetry (DSC) results. The eutectic materials were characterized by powder X-ray diffraction (PXRD) and polarized light optical microscopy (OM). The hygroscopicity of the materials was assessed at different relative humidities (RH) through dynamic vapor sorption (DVS). The dissolution study was conducted with the materials in powder form, with paddle dissolution, rotating at 50 rpm, in 900 mL of aqueous buffer solution at pH 6.8 and 37 °C. The phase diagrams demonstrated that EZT formed eutectic systems with eutectic molar fractions of 0.59, 0.67 and 0.69 for EZT-SCA, EZT-NTM and EZT-MPB, respectively. The three eutectic materials are characterized as microcrystalline conglomerates of their components. In terms of the hygroscopic behavior of EZT at different RHs, eutectic materials demonstrated lower susceptibility to monohydrate formation compared to the anhydrous form. In dissolution studies, EZT-SCA and EZT-MPB solubilized EZT in amounts 22 % higher than the pure drug in 15 min. On the other hand, EZT-NTM eutectic suppressed the dissolution of EZT down to 56 % at the same time. The results indicated the possibility of obtaining materials with enhanced properties using eutectic mixtures, with improved dissolution rates and hygroscopic stability.