Release Rate Research Articles

Thermo-responsive composite nanoparticles based on hydroxybutyl chitosan oligosaccharide: Fabrication, stimulus release and cancer therapy

Designing thermo-responsive nanocarriers based on biopolymers is fascinating and challenging for cancer therapy. In this study, thermo-responsive composite nanoparticles (CNPs) were prepared using hydroxybutyl chitosan oligosaccharide (HBCOS) and sodium caseinate (SC) via electrostatic interactions and covalent crosslinking. The temperature-responsive behaviors of CNPs were induced by the breakage of hydrogen bonds and the shrinkage of chains in nanoparticles. The CNPs exhibited concentration-independent thermo-responsive behavior, non-adsorption aggregation, and non-hemolysis, suggesting excellent stability and thermo-sensitivity. The initial release rate and final amount of DOX released from CNPs at 42 °C were higher than that at 37 °C, showing a thermo-responsive release, which was also more prominent at lower pH. The release of DOX from CNPs followed first order kinetics based on Fickian diffusion. In vitro cytotoxicity assays confirmed the thermo-responsive antitumor activity of DOX-loaded CNPs as the HT-29 cell viability incubated with DOX-loaded CNPs at 42 °C was significantly lower than that at 37 °C. Cellular uptake experiments proved that DOX-loaded CNPs accumulated in the cytoplasm after being endocytosed and promoted DOX release by increasing environment temperature. This study generated stable thermo-sensitive CNPs based on biopolymers, which can be used as potential nanocarriers for the controlled release of anticancer drugs for cancer therapy.

Thiolated chitosan nanoparticles encapsulated nisin and selenium: antimicrobial/antibiofilm/anti-attachment/immunomodulatory multi-functional agent

BackgroundThe increase in the resistance of bacterial strains to antibiotics has led to research into the bactericidal potential of non-antibiotic compounds. This study aimed to evaluate in vitro antibacterial/ antibiofilm properties of nisin and selenium encapsulated in thiolated chitosan nanoparticles (N/Se@TCsNPs) against prevalent enteric pathogens including standard isolates of Vibrio (V.) cholerae O1 El Tor ATCC 14,035, Campylobacter (C.) jejuni ATCC 29,428, Salmonella (S.) enterica subsp. enterica ATCC 19,430, Shigella (S.) dysenteriae PTCC 1188, Escherichia (E.) coli O157:H7 ATCC 25,922, Listeria (L.) monocytogenes ATCC 19,115, and Staphylococcus (S.) aureus ATCC 29,733.MethodsThe synthesis and comprehensive analysis of N/Se@TCsNPs have been completed. Antibacterial and antibiofilm capabilities of N/Se@TCsNPs were evaluated through broth microdilution and crystal violet assays. Furthermore, the study included examining the cytotoxic effects on Caco-2 cells and exploring the immunomodulatory effects of N/Se@TCsNPs. This included assessing the levels of both pro-inflammatory (IL-6 and TNFα) and anti-inflammatory (IL-10 and TGFβ) cytokines and determining the gene expression of TLR2 and TLR4.ResultsThe N/Se@TCsNPs showed an average diameter of 136.26 ± 43.17 nm and a zeta potential of 0.27 ± 0.07 mV. FTIR spectroscopy validated the structural features of N/Se@TCsNPs. Scanning electron microscopy (SEM) images confirmed their spherical shape and uniform distribution. Thermogravimetric Analysis (TGA)/Differential Scanning Calorimetry (DSC) tests demonstrated the thermal stability of N/Se@TCsNPs, showing minimal weight loss of 0.03%±0.06 up to 80 °C. The prepared N/Se@TCsNPs showed a thiol content of 512.66 ± 7.33 µmol/g (p < 0.05), an encapsulation efficiency (EE) of 69.83%±0.04 (p ≤ 0.001), and a drug release rate of 74.32%±3.45 at pH = 7.2 (p ≤ 0.004). The synthesized nanostructure demonstrated potent antibacterial activity against various isolates, with effective concentrations ranging from 1.5 ± 0.08 to 25 ± 4.04 mg/mL. The ability of N/Se@TCsNPs to reduce bacterial adhesion and internalization in Caco-2 cells underscored their antibiofilm properties (p ≤ 0.0001). Immunological studies indicated that treatment with N/Se@TCsNPs led to decreased levels of inflammatory cytokines IL-6 (14.33 ± 2.33 pg/mL) and TNFα (25 ± 0.5 pg/mL) (p ≤ 0.0001), alongside increased levels of anti-inflammatory cytokines IL-10 (46.00 ± 0.57 pg/mL) and TGFβ (42.58 ± 2.10 pg/mL) in infected Caco-2 cells (p ≤ 0.0001). Moreover, N/Se@TCsNPs significantly reduced the expression of TLR2 (0.22 ± 0.09) and TLR4 (0.16 ± 0.05) (p < 0.0001).ConclusionIn conclusion, N/Se@TCsNPs exhibited significant antibacterial/antibiofilm/anti-attachment/immunomodulatory effectiveness against selected Gram-positive and Gram-negative enteric pathogens. However, additional ex-vivo and in-vivo investigations are needed to fully assess the performance of nanostructured N/Se@TCsNPs.

Fluconazole adsorption and release study using KIT-6 for targeted and controlled drug delivery system

ABSTRACT This study presents the development of a mesoporous silica, i.e. KIT-6 synthesised using the hydrothermal technique, followed by the loading of fluconazole as the model drug using the post-impregnation method. The results of drug entrapment studies exposed that 76% of the drug was entrapped in the silica matrix. The drug release rate was investigated in phosphate buffer with pH = 6.8. The fluconazole-loaded KIT-6 prolonged the drug’s release for 12 hours, ensuring Higuchi’s square root kinetics, with diffusion via the matrix as the releasing mechanism, which revealed that the release rate was under control. The MTT assay-based biocompatibility experiments on Vero cells show that the pure and drug-loaded composite systems have minimal cytotoxicity. Hence, drug delivery and adsorption may be facilitated, and repeated administration of drugs is reduced by a controlled drug release rate using the prepared silicious composite.

Fluconazole adsorption and release study using KIT-6 for targeted and controlled drug delivery system

ABSTRACT This study presents the development of a mesoporous silica, i.e. KIT-6 synthesised using the hydrothermal technique, followed by the loading of fluconazole as the model drug using the post-impregnation method. The results of drug entrapment studies exposed that 76% of the drug was entrapped in the silica matrix. The drug release rate was investigated in phosphate buffer with pH = 6.8. The fluconazole-loaded KIT-6 prolonged the drug’s release for 12 hours, ensuring Higuchi’s square root kinetics, with diffusion via the matrix as the releasing mechanism, which revealed that the release rate was under control. The MTT assay-based biocompatibility experiments on Vero cells show that the pure and drug-loaded composite systems have minimal cytotoxicity. Hence, drug delivery and adsorption may be facilitated, and repeated administration of drugs is reduced by a controlled drug release rate using the prepared silicious composite.

ROS-responsive charge reversal mesoporous silica nanoparticles as promising drug delivery system for neovascular retinal diseases

Intravitreal injection of biodegradable implant drug carriers shows promise in reducing the injection frequency for neovascular retinal diseases. However, current intravitreal ocular devices have limitations in adjusting drug release rates for individual patients, thereby affecting treatment effectiveness. Accordingly, we developed mesoporous silica nanoparticles (MSNs) featuring a surface that reverse its charge in response to reactive oxygen species (ROS) for efficient delivery of humanin peptide (HN) to retinal epithelial cells (ARPE-19). The MSN core, designed with a pore size of 2.8 nm, ensures a high HN loading capacity 64.4% (w/w). We fine-tuned the external surface of the MSNs by incorporating 20% Acetyl-L-arginine (Ar) to create a partial positive charge, while 80% conjugated thioketal (TK) methoxy polyethylene glycol (mPEG) act as ROS gatekeeper. Ex vivo experiments using bovine eyes revealed the immobilization of Ar-MSNs-TK-PEG (mean zeta potential: 2 mV) in the negatively charged vitreous. However, oxidative stress reversed the surface charge to −25 mV by mPEG loss, facilitating the diffusion of the nanoparticles impeded with HN. In vitro studies showed that ARPE-19 cells effectively internalize HN-loaded Ar-MSNs-TK, subsequently releasing the peptide, which offered protection against oxidative stress-induced apoptosis, as evidenced by reduced TUNEL and caspase3 activation. The inhibition of retinal neovascularization was further validated in an in vivo oxygen-induced retinopathy (OIR) mouse model.

Lightweight, high-strength and fireproof borax-crosslinked graphene/hydroxyethyl cellulose hybrid aerogels fabricated via ice template method

In recent years, there has been a growing interest in fireproof nanomaterials due to their broad applications in fire-safety and environmental preservation. In this study, one kind of lightweight fireproof hybrid aerogel with low thermal conductivity (0.039 W/m•K) was prepared through a facile ice template method, where the graphene nanosheets and hydroxyethyl cellulose (HEC) are combined with borax crosslinkers. It was found that this aerogel can be not only recyclable and repairable, but also possesses excellent compressive strength and stiffness, owing to the interfacial van der Waals adsorption, ionic crosslinking and hydrogen bonding interactions. Remarkably, it has excellent flame retardancy performance (an extremely low peak heat release rate (PHRR) was measured to be 37.44 kW/m2, reduced by 88.6 % comparing to that of graphene/HEC aerogel). To further explore the fire resistance mechanism of this aerogel, the molecular dynamics simulation was performed. It reveals that the borax can effectively wrap and hinder the graphene and HEC molecules from decomposition. Besides, the borax can compact graphene and HEC closer, thereby further isolating heat and oxygen, realizing the fireproof property. This study offers valuable insights for designing advanced fireproof nanomaterials and applications in shipbuilding or construction.

Spray-dried microparticles of turmeric extract for improved delivery and low toxicity

This study aimed to enhance the delivery of turmeric by encapsulating its extract within microparticles using chitosan and mannitol through the spray drying technique and to assess their acute oral toxicity. The resulting microparticles were spherical, with an average diameter of 4 microns, and comprised 17% curcuminoids and 4% ar-turmerone. In vitro studies demonstrated that these microparticles had a higher release rate of curcuminoids compared to raw turmeric extract and preserved antioxidant activity. In the acute toxicity study, conducted in Wistar rats with a single dose of 2,000 mg/kg, no acute toxic symptoms were observed. According to the Globally Harmonized System of Classification and Labeling of Chemicals, the microparticles were categorized as having relatively low acute toxicity (category 5). These findings support the potential utility of the microparticles in dietary supplements and pharmaceutical applications due to their effective delivery properties and safety profile.

Asymmetric nanofracture in WS2 for its local toughness anisotropy

Abstract Fracture in crystal lattices usually occurs with discrete atomic bond breakages around the crack tip. WS2 involves three-layer atomic structures, where the atomic stress near the crack front exhibits thickness dependence and significantly relies on the local distortion of lattice geometry. We show that the T-stress obtained by over-deterministic methods, and the continuum circumferential stress, are limited in predicting the nanocrack kinking of WS2 strips by molecular dynamics simulations. As the far-field displacement loads, the T-stress initially increases in negative, followed by a slight jump at the initiation of kinking, and the continuum circumferential stress cannot accurately capture the variation of atomic stresses at the crack tip. This can be attributed to the local anisotropy in atomic lattices, and the crack preferentially extends in the zigzag direction of the local maximum energy release rate. Our work might provide insights into the fabrication and assembly of WS2 nanodevices.

A numerical investigation on the effect of altering compression ratio, injection timing, and injection duration on the performance of a diesel engine fuelled with diesel-biodiesel-butanol blend

Abstract Using renewable fuels for diesel engines can reduce both air pollution and dependence on fossil fuels. A computer simulation was constructed to predict the performance, combustion characteristics, and NOx emission of a diesel engine fuelled with diesel-biodiesel-butanol blends. The simulation was validated by comparing the modeling results against experimental data and a good agreement between the results was found. The fuels used for the validation were diesel (B0), biodiesel (B100), diesel-biodiesel blend (B50), and two diesel-biodiesel-butanol blends with 45% diesel-45% biodiesel-10% butanol (Bu10), and 40% diesel-40% biodiesel-20% butanol (Bu20) by volume. Experimental results showed that the addition of butanol reduced NOx emissions but deteriorated the engine performance. The aim of the current work was the numerical optimization of the different parameters to enhance the engine performance while using butanol to decrease NOx emissions. The engine compression ratio (CR) varied from 14 to 24, in increments of 2. Fuel injection timing (IT) was retarded from 30° before top dead center (bTDC) to 5° bTDC in increments of 5o. Also, the fuel injection duration (IDur) was extended from 20° to 50° in increments of 10°. Results showed that the increase in CR improved engine performance for the two investigated fuels, Bu10 and Bu20. The maximum engine brake power (BP), thermal efficiency (BTE), and minimum brake-specific fuel consumption (BSFC) of 1.46 kW, 32.3%, and 0.273 kg/kWh respectively, were obtained when the Bu10 fuel was injected at the optimum conditions of 24 CR, 15°bTDC IT, and 40° injection duration (IDur). Under these optimum conditions, the BP, BTE, and BSFC improved by 3% to 3.5% for Bu10 and Bu20 fuel blends compared to the base engine conditions of CR of 22, 30° IDur, and 10° bTDC IT. The heat release rate during the premixed phase increased when the IT was advanced, while the mixing-controlled combustion phase was enhanced when the IT was retarded. NOx emissions increased with increasing the CR, while both the increase in IDur at constant IT and the retard of IT decreased engine NOx emissions. At the optimum conditions, the NOx emissions for Bu10 and Bu20 were further decreased by 2.2% and 0.9% respectively compared to the experimental results at base engine conditions. Retarding the injection timing from 15° bTDC to 5° bTDC at a CR of 24 and IDur of 40° caused the NOx emissions for Bu10 and Bu20 to decrease by 16%. When the injection duration was increased from 20° to 50° at a CR of 24 and an IT of 15°bTDC, the NOx emissions for Bu10 and Bu20 decreased by 12.3% and 11.8% respectively. The addition of butanol to the diesel-biodiesel blend at optimum conditions showed results comparable to pure diesel, with a decrease in NOx emissions.

Investigation of Split Diesel Injections in Methanol/Diesel Dual-Fuel Combustion in an Optical Engine

Methanol is a promising alternative fuel due to its wide availability of raw materials, mature production processes, and low production cost. However, because of the low cetane number, methanol must include a more reactive fuel to assist with combustion when used in compression ignition (CI) engines. In this study, based on the optical CI engine platform, methanol is injected into the intake port, and diesel is directly injected into the cylinder to achieve dual-fuel combustion. The effects of the methanol energy ratios and diesel split injection strategies on combustion are investigated. The results show that the premixed blue flame was mainly concentrated in the near wall region, whereas the yellow flame produced by diesel combustion tended to concentrate in the central region as the methanol energy ratio increased. When the methanol energy ratio exceeded 50%, the ignition delay was significantly prolonged, while the flame area was greatly reduced. Meanwhile, the peak values for the cylinder pressure and heat release rate decreased significantly, indicating a significant deterioration in combustion. At the earlier diesel pre-injection timing at −58°, the overall dual-fuel combustion at each main injection timing exhibited low-temperature premixed combustion characteristics, with a lower peak exothermic rate and flame brightness. At the later pre-injection timing at −33°, the spray flame at all main injection timings could be observed, with higher peak heat release rates and indications of thermal efficiency. Combustion at later main injection timings was characterized by diffusion combustion, and the main injection timing could effectively regulate the combustion process through phase adjustment.

Characterization of Fuel Pellets Made From Rice Husk, Sawdust and Corncob Bond with Cissus Populnea and Manihot Esculenta

There is growing interest in the production of biofuels from biomass wastes. The availability of biomass waste poses the need for technical assessment of pelletisation of biomass waste at industrial production level. The misuse of environmentally friendly and sustainable energy resources and lack of compressed biomass energy products that could enhance fuel quality needs to be addressed. This study intends to determine the energy output from tenary combination of the biomass fuel pellets consisting of rice husks, African birch sawdust, corncobs and their varying mixtures bond with aqueous extract of C. populnea (Cp) and M. esculenta (Me). The combustion characteristics of pellets produced from Rice Husk, African Birch Sawdust, Corncob and their blends (M, M1, M2, M3 and M4) were conducted by the development of an analytical protocol. Pellet admixtures were prepared at each binder ratio of 10% of bulk weight of RH, ABS, corncob and their various blends in the ratios 1:1:1 (M), 1:2:3 (M1), 2:1:3 (M2), 3:1:2 (M3) and 2:3:1 (M4), respectively. The Bulk Density (BD), Ash Contents (AC), Heat Release Rate (HRR) and Calorific Value (CV) of the pellets were measured using established procedures. The result revealed that combustion characteristics of fuel pellets made from Corncob and Blend ratio of 1:2:3 bound with Manihot esculenta gel were enhanced and the fuel pellets possessed sufficient calorific values suitable for energy applications. It was recommended that massive production of fuel pellets from biomass wastes for small and medium scale energy systems could give a positive development to agrarian and rural areas in Nigeria where there is a lot of these resources and lack of stable electrical supply.

Interaction of acoustic pressure and heat release rate fluctuations in a model rocket engine combustor

Interaction of acoustic pressure and heat release rate fluctuations in a model rocket engine combustor

Mechanism of phosphate release from actin filaments

After ATP-actin monomers assemble filaments, the ATP's [Formula: see text]-phosphate is hydrolyzedwithin seconds and dissociates over minutes. We used all-atom molecular dynamics simulations to sample the release of phosphate from filaments and study residues that gate release. Dissociation of phosphate from Mg2+ is rate limiting and associated with an energy barrier of 20 kcal/mol, consistent with experimental rates of phosphate release. Phosphate then diffuses within an internal cavity toward a gate formed by R177, as suggested in prior computational studies and cryo-EM structures. The gate is closed when R177 hydrogen bonds with N111 and is open when R177 forms a salt bridge with D179. Most of the time, interactions of R177 with other residues occlude the phosphate release pathway. Machine learning analysis reveals that the occluding interactions fluctuate rapidly, underscoring the secondary role of backdoor gate opening in Pi release, in contrast with the previous hypothesis that gate opening is the primary event.

Mechanism of phosphate release from actin filaments

After ATP-actin monomers assemble filaments, the ATP's [Formula: see text]-phosphate is hydrolyzedwithin seconds and dissociates over minutes. We used all-atom molecular dynamics simulations to sample the release of phosphate from filaments and study residues that gate release. Dissociation of phosphate from Mg2+ is rate limiting and associated with an energy barrier of 20 kcal/mol, consistent with experimental rates of phosphate release. Phosphate then diffuses within an internal cavity toward a gate formed by R177, as suggested in prior computational studies and cryo-EM structures. The gate is closed when R177 hydrogen bonds with N111 and is open when R177 forms a salt bridge with D179. Most of the time, interactions of R177 with other residues occlude the phosphate release pathway. Machine learning analysis reveals that the occluding interactions fluctuate rapidly, underscoring the secondary role of backdoor gate opening in Pi release, in contrast with the previous hypothesis that gate opening is the primary event.

Effect of Surfactants on the Synthesis and Dissociation of Gas Hydrates

The synthesis and dissociation of methane hydrate and carbon dioxide hydrate were studied. Nonflammable gas hydrates can be used to extinguish flames in confined spaces. To increase the extinguishing efficiency, it is necessary to increase the dissociation rate (gas release rate) by using surfactant. The work investigates gas hydrates synthesized using sodium dodecyl sulfate (SDS). Experimental studies were carried out in wide ranges of surfactant concentration, the number of the stirrer revolutions and the initial water volume. To achieve the maximum rate of synthesis and dissociation, optimization of the specified parameters was performed. The influence of the key parameters on the dissociation rate was investigated experimentally and theoretically. The novelty of the work lies in solving a complex of interrelated tasks on the synthesis and dissociation of gas hydrate. It is shown that in order to achieve the maximum dissociation rate of carbon dioxide hydrate, it is necessary to optimize the following parameters: the diameter of the particles and their porosity, the porosity of the layer and the external heat flux.

DEVELOPMENT OF ZINC-LOADED HYDROGEL INFUSED WITH ALOE BARBADENSIS MUCILAGE FOR WOUND HEALING

This study aims to formulate and characterize zinc-loaded hydrogel infused with Aloe barbadensis mucilage for wound dressing. Five formulations containing varying proportions of carbopol, zinc, aloe and water (as vehicle) were developed via physical crosslinking using triethanolamine. All formulations had a translucent off-white colour while the control gave a transparent gel. The viscosity was highest in the control, 30000.00 ± 2.07 PaS. The pH of the formulations was between 5.7 and 5.8. Formulation 2 which is composed of 30 mg of Zinc and 1.4 mg of Aloe barbadensis incorporated into 1% w/v Carbopol Ultrez hydrogel polymer had the lowest swelling index of 79.2 ± 1.95% implying that it had the fastest drug release rate. The wounds treated with Formulation 2 had the most rapid wound healing with no sign of scars in the wound area. Histomorphometric evaluation reflected a high re-epithelisation rate of 70%, a significant percentage occupied by collagen in granulation tissue of 85%. The thickness of the tissue's central region was 10 mm. The inflammatory cells /mm2 tissue was 200 cells/mm2 while the number of microvessels in granulation tissue was 1.0 microvessels/mm2. Zinc-loaded hydrogel infused with Aloe barbadensis mucilage shows great potential as a modern wound dressing.

DEVELOPMENT OF ZINC-LOADED HYDROGEL INFUSED WITH ALOE BARBADENSIS MUCILAGE FOR WOUND HEALING

This study aims to formulate and characterize zinc-loaded hydrogel infused with Aloe barbadensis mucilage for wound dressing. Five formulations containing varying proportions of carbopol, zinc, aloe and water (as vehicle) were developed via physical crosslinking using triethanolamine. All formulations had a translucent off-white colour while the control gave a transparent gel. The viscosity was highest in the control, 30000.00 ± 2.07 PaS. The pH of the formulations was between 5.7 and 5.8. Formulation 2 which is composed of 30 mg of Zinc and 1.4 mg of Aloe barbadensis incorporated into 1% w/v Carbopol Ultrez hydrogel polymer had the lowest swelling index of 79.2 ± 1.95% implying that it had the fastest drug release rate. The wounds treated with Formulation 2 had the most rapid wound healing with no sign of scars in the wound area. Histomorphometric evaluation reflected a high re-epithelisation rate of 70%, a significant percentage occupied by collagen in granulation tissue of 85%. The thickness of the tissue's central region was 10 mm. The inflammatory cells /mm2 tissue was 200 cells/mm2 while the number of microvessels in granulation tissue was 1.0 microvessels/mm2. Zinc-loaded hydrogel infused with Aloe barbadensis mucilage shows great potential as a modern wound dressing.

Release Kinetics of Sulfentrazone from Chitosan Clay Sulfentrazone Nanocomposite

Introduction: With a rational objective to reduce groundwater contamination from pesticides and thereby reducing ecotoxicological effect of pesticide, present research programme was carried out. Sulfentrazone is a well-known effective pesticide that is used for soybean crops. But at the same time, sulfentrazone is known for its high leaching potential through soil and could lead to ground water contamination Method: So we have synthesized a novel chitosan clay nanocomposites of sulfentrazone at three different concertations of sulfentrazone, 37.64%, 52.44% and 59.85% and its release pattern was studied at three different buffer systems like pH 2, pH 4 and pH 6. Release pattern of Sulfentrazone has been quantified by using High Performance Liquid Chromatography (HPLC) technique. Various mathematical tools have been applied to understand the release kinetics of chitosan clay sulfentrazone nanocomposites Result: Correlation coefficient (R2) of many models has been plotted and the Huguchi model was found to be the most suitable for these nanocomposites. The salient finding of this study is that the release rates of sulfentrazone at pH 4 is 68.39%, 42.62% and 37.75% after 8 hours at three different loading. This release pattern is higher than the release pattern at pH 6 and pH 2. Conclusion: Based on these release data, it is very clear that chitosan clay sulfentrazone nanocomposite can control the release of sulfentrazone at regular soil pH conditions, which is pH 6.

Temperature evolution and flame behavior inside a ceiling-vented compartment with different fire source locations under the effect of wind

This work presents an experimental investigation on ceiling-vented compartment fire behavior and thermal characteristics with different fire source locations under the effect of wind associated by CFD simulations. Experiments were carried out under the ambient wind condition, and the fire source was respectively set at windward side, center and leeward side. Results show that: (1) In no-wind cases, a critical heat release rate is found at which the inside temperature decreases with the increasing of fire heat release rate indicating flame flows outside. The critical HRR for fire source attached to sidewall is slightly larger than that when the fire source is located at compartment center, and it increases as vent dimension increases. (2) In ambient wind condition, there is a travelling process that the flame transfers from windward side to leeward side with the increasing of fire HRR. The critical HRR for the transition increases as vent size increases, and decreases as wind speed increases, and is basically independent of fire source location, which is proved to be related to air inflow rate. A Froude number is proposed to characterize the wind effect based on air inflow analysis, and the critical HRR for transition is represented well by the Froude number.

Synthesis and Polymerization of the Bio‐Benzoxazine Derived from Resveratrol and Thiophenemethylamine and Properties of its Polymer

AbstractResveratrol and 2‐thiophenemethylamine have been employed in the synthesis of a novel tri‐functional benzoxazine (RES‐th) to develop the bio‐benzoxazine monomer. The chemical structure of the synthesized monomer is confirmed by various characterization technics. The polymerization behavior is monitored by in situ Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). The in situ FTIR results reveal distinct reaction mechanisms for the three oxazine rings presented in RES‐th, with both ether and phenolic Mannich bridge structures observed in the products. The activation energy values of RES‐th are calculated to be 119.05, 120.97, and 119.44 kJ mol−1 by Kissinger, Ozawa, and Starink methods, respectively, which are all based on the heat flow curves at various heating temperatures. The thermal stability and flame retardancy of the resulting polybenzoxazine (poly(RES‐th)) are investigated by thermogravimetric analysis (TGA) and microscale combustion calorimeter (MCC). The values of Td5 and Td10 of polybenzoxazine are found to be 356 °C and 399 °C, respectively, with a char yield of 66.3% at 800 °C. The prepared polybenzoxazine also demonstrates nonflammability characteristics with the values of heat release capacity (HRC) and total heat release rate (THR) of 18.65 J (g K)−1 and 2.69 kJ g−1, respectively. These findings suggest that the thermoset, poly(RES‐th), is a promising candidate for fire‐resistant applications.