Continuous Bamboo Fibers/Fire-Retardant Polyamide 11: Dynamic Mechanical Behavior of the Biobased Composite

A biobased composite was generated from bamboo fibers (BF) and a polyamide 11 (PA11) matrix. In order to fulfill security requirements, a PA11 already containing a flame retardant (FR) was chosen: This matrix is referred as PA11-FR. In this work, the effects of flame retardant (melamine cyanurate) on the composite properties were considered. In the calorimetric study, the glass transition and melting temperatures of PA11-FR were the same as those of PA11. The melamine cyanurate (MC) had no influence on these parameters. Thermogravimetric analysis revealed that PA11-FR was less stable than PA11. The presence of MC facilitated thermal decomposition regardless of the analysis atmosphere used. It is important to note that the presence of FR did not influence processing conditions (especially the viscosity parameter) for the biosourced composite. Continuous BF-reinforced PA 11-FR composites, single ply, with 60% of fibers were processed and analyzed using dynamic mechanical analysis. In shear mode, comparative data recorded for BF/PA11-FR composite and the PA11-FR matrix demonstrated that the shear glassy modulus was significantly improved: multiplied by a factor of 1.6 due to the presence of fibers. This result reflected hydrogen bonding between reinforcing fibers and the matrix, resulting in a significant transfer of stress. In tensile mode, the conservative modulus of BF/PA11-FR reached E’ = 8.91 GPa. Upon BF introduction, the matrix tensile modulus was multiplied by 5.7. It can be compared with values of a single bamboo fiber recorded under the same experimental conditions: 31.58 GPa. The difference is partly explained by the elementary fibers’ lack of alignment in the composite.

Thermal Behaviour of Microgels Composed of Interpenetrating Polymer Networks of Poly(N-isopropylacrylamide) and Poly(Acrylic Acid): A Calorimetric Study

Stimuli-responsive microgels have recently attracted great attention in fundamental research as their soft particles can be deformed and compressed at high packing fractions resulting in singular phase behaviours. Moreover, they are also well suited for a wide variety of applications such as drug delivery, tissue engineering, organ-on-chip devices, microlenses fabrication and cultural heritage. Here, thermoresponsive and pH-sensitive cross-linked microgels, composed of interpenetrating polymer networks of poly(N-isopropylacrylamide) (PNIPAM) and poly(acrylic acid) (PAAc), are synthesized by a precipitation polymerization method in water and investigated through differential scanning calorimetry in a temperature range across the volume phase transition temperature of PNIPAM microgels. The phase behaviour is studied as a function of heating/cooling rate, concentration, pH and PAAc content. At low concentrations and PAAc contents, the network interpenetration does not affect the transition temperature typical of PNIPAM microgel in agreement with previous studies; on the contrary, we show that it induces a marked decrease at higher concentrations. DSC analysis also reveals an increase of the overall calorimetric enthalpy with increasing concentration and a decrease with increasing PAAc content. These findings are discussed and explained as related to emerging aggregation processes that can be finely controlled by properly changing concentration, PAAc content an pH. A deep analysis of the thermodynamic parameters allows to draw a temperature– concentration state diagram in the investigated concentration range.

Analysis of the Possibility of Management of Curly-Leaf Pondweed for Energetic Purposes

The possibilities of using curly-leaf pondweed for energy purposes were analyzed. This plant contributes to overgrowth of water reservoirs, causing their eutrophication. The plants examined were from two different water reservoirs: Lake Winiary (Gniezno) and Lake Rusalka (Poznan). On the basis of the investigations, it was determined that it is possible to use curly-leaf pondweed for energy purposes, both in the combustion method and in the biomethane fermentation process. Studies were performed to assess the suitability of the plants for combustion as a solid biofuel and studies on the use of pondweed as a fermenter feedstock. The calorimetric study showed the possibility of obtaining more energy for the curly-leaf pondweed coming from Lake Rusalka. The heat of combustion of these plants was 13.95 MJ·kg−1 (Winiary pondweed) and 9.10 MJ·kg−1 (Rusalka pondweed). On the other hand, the calorific value of these plants was 12.60 MJ·kg−1 (Winiary pondweed) and 7.80 MJ·kg−1 (Rusalka pondweed). In the case of biogas yield studies, significantly higher biogas production was observed for Lake Rusalka pondweed than for Lake Winiary pondweed. The total biogas yield for these plants was 8.05 m3·Mg−1 for Rusalka pondweed and 3.19 m3·Mg−1 for Winiary pondweed. Differences in the chemical composition of pondweed originating from different lakes were also found, which translated into differences in the amount of energy that could be obtained from plants from both stands.

Effect of Boron and Water-to-Cement Ratio on the Performances of Laboratory Prepared Belite-Ye’elimite-Ferrite (BYF) Cements

The effect of superplasticiser, borax and the water-to-cement ratio on BYF hydration and mechanical strengths has been studied. Two laboratory-scale BYF cements—st-BYF (with β-C2S and orthorhombic C4A3S¯) and borax-activated B-BYF (with α’H-C2S and pseudo-cubic C4A3S¯)—have been used, and both show similar particle size distribution. The addition of superplasticiser and externally added borax to BYF pastes has been optimised through rheological measurements. Optimised superplasticiser contents (0.3, 0.4 and 0.1 wt % for st-BYF, B-BYF and st-BYF with externally added 0.25 wt % B2O3, respectively) result in low viscosities yielding homogeneous mortars. The calorimetric study revealed that st-BYF is more reactive than B-BYF, as the values of heat released are 300–370 J/g and 190–210 J/g, respectively, after 7 days of hydration; this fact is independent of the water-to-cement ratio. These findings agree with the higher degree of hydration at 28 days of β-C2S in st-BYF (from 45 to 60%) than α’H-C2S in B-BYF (~20 to 30%). The phase assemblage evolution has been determined by LXRPD coupled with the Rietveld method and MAS-NMR. The formation of stratlingite is favoured by increasing the w/c ratio in both systems. Finally, the optimisation of fresh BYF pastes jointly with the reduction of water-to-cement ratio to 0.40 have allowed the achieving of mortars with compressive strengths over 40 MPa at 7 days in all systems. Moreover, the st-BYF mortar, where borax was externally added, achieved more than 70 MPa after 28 days. The main conclusion of this work does not support Lafarge’s approach of adding boron/borax to the raw meal of BYF cements. This procedure stabilises the alpha belite polymorph, but its reactivity, in these systems, is lower and the associated mechanical strengths poorer.

Preparation and Characterization of Eco-Friendly Spent Coffee/ENR50 Biocomposite in Comparison to Carbon Black

This study investigates the impact of spent coffee biochar (Biochar) compared to carbon black (CB) as a partial replacement for carbon black in epoxidized natural rubber (ENR). Particle size and elemental analysis were used to characterize the biochar and CB. Cure characteristics, tensile, thermal, and morphological properties on the effect of biochar and CB as filler were studied. It was found that incorporating 10 phr of spent coffee biochar could improve the composites’ tensile properties and thermal performance compared to carbon black. However, the addition of biochar significantly affects the maximum torque compared to CB and delays the vulcanization time. SEM study shows that biochar has a strong effect on the morphology of composite films. The FTIR graph reveals no substantial difference between compounds with biochar and CB. According to the thermal calorimetric study, the thermal stability of ENR-Biochar is higher than that of ENR-CB. Additionally, these findings suggest that the utilization of spent coffee as a sustainable biochar could be further explored, but little has been done in epoxidized natural rubber (ENR).

Effect of cryogenic freezing on the rheological and calorimetric properties of pasteurized liquid egg yolk

The egg yolk undergoes an irreversible gelation process when freezing to –6 °C or lower. In this experiment, liquid egg yolk (LEY) was frozen in liquid nitrogen and stored at –18 °C for 150 days. The measurement of pH and colour of LEY were performed. The examination of the rheological and calorimetric properties of samples was also carried out. The results indicated that the pH of LEY changed significantly during frozen storage, increasing from 6.37 ± 0.02 to 6.58 ± 0.03 over five months. The colour of the samples also showed a significant change compared to the fresh sample. The rheological properties of the LEY also changed significantly after 1 day of freezing and during frozen storage, with a clear increasing trend of the yield stress. The results of the calorimetric study showed that freezing and frozen storage did not affect the denaturation temperature, however, the denaturation enthalpy was reduced by about half after five months of frozen storage.

Drug-Excipients Compatibility Studies in Proniosomal Formulation: A Case Study with Resveratrol

Proniosomal drug delivery system is one of the advancements in nanotechnology. Similarly to traditional dosage forms, chemical and physical compatibility of proniosomes components with the active ingredient(s) is a key step in the preformulation process of such systems. In this work, the compatibility of resveratrol with selected excipients in the development of proniosomal formulation was investigated by thermal and spectroscopic techniques. To evaluate the drug-excipient compatibility, different techniques such as differential scanning calorimetric study, attenuated total reflectance Fourier transform infrared spectroscopy study and powder X-ray diffraction were adopted. The results showed that the excipients used in the formulation were compatible with resveratrol.