Oxygen Index Research Articles

A novel phosphorus/boron-containing flame retardant for improving the flame retardancy of ramie fiber reinforced epoxy composites

As a kind of plant fiber, ramie fibers (RFs) are widely used in fiber reinforced resin matrix composites, however, both of RFs and resin matrix are flammable. Enhancing the flame retardancy of ramie fiber reinforced epoxy composites is important. In this study, a highly efficient flame retardant, PBXY, was synthesized from phytic acid, boric acid, and xylitol to improve the flame retardancy of ramie fibers, and flame-retardant ramie fiber reinforced epoxy composites (EP/RF-PBXYs) with different weight gain were prepared by coating PBXY on the surface of ramie fibers. The effects of different weight gain of PBXY on the thermal stability, flame retardancy, and mechanical properties of EP/RF-PBXYs were investigated. Compared with that of EP/RF, the limiting oxygen index value of EP/RF-PBXY2 was increased from 23.0% to 31.4% and a UL-94 V-0 rating was obtained, the total heat release and total smoke production were reduced by 33.2% and 31.0%. However, the presence of PBXY had a negative effect on the mechanical properties of EP/RF when the weight gain of PBXY was more than 10wt% (related to RFs). This study offers a promising avenue to improve the flame-retardant resistance of EP/RF.

Enhanced flame retardancy and mechanical properties of poly (lactic acid) composites via piperazine pyrophosphate and nanoscale cerium dioxide synergistic flame retarding and uniaxial pre-stretching

The simultaneous improvement of flame retardancy and mechanical properties (including strength, rigidity, and toughness) of PLA was achieved for the first time. A synergistic flame retardant system including PAPP and nano-CeO2 was used to enhance the flame retardant properties of PLA. Especially, uniaxial pre-stretching was further used to improve the mechanical properties of the flame-retardant PLA composites. With the addition of just 1 wt% nano-CeO2, the flame retardant properties of PLA composite were significantly enhanced. Relative to pure PLA, the limiting oxygen index (LOI) of PLA/14 wt%PAPP/1 wt% nano-CeO2 increased from 20.2 % to 28.8 %, achieving a V-0 rating in the UL-94 test. Moreover, the peak heat release rate (PHRR) was reduced from 461KW/m2 to 230KW/m2. Notably, the flame-retardant PLA composites with excellent mechanical properties were achieved using uniaxial pre-stretching for the first time. After pre-stretching, the tensile strength, elongation at break and impact strength of the flame-retardant PLA were significantly increased to 79.82 MPa, 103.8 %, and 9.7 kJ/m2, respectively. This work proposes an ingenious strategy for significantly enhancing both the fire safety and mechanical properties of PLA composites.

Rigid polyurethane foam with durable hydrophobicity and flame retardancy endowed by novel functional surfactants

Traditional rigid polyurethane foam (RPUF) with flame retardancy might be easily damaged in some moist condition due to its hydrophobicity, which would lead to unsafety. Therefore, novel surfactants with both hydrophobic fluorinated group and flame-retardant phosphorus group were synthesized. With lower surface tension and more hydrogen bonds formed in polyurethane, the mixed surfactants, which were used in the preparation of RPUF, have not only obviously improved the size uniformity and integrity of cells but also enhanced its hydrophobicity, compressive strength and thermal insulating performance. Besides, effective ‘protection’ could be constructed on the surface of RPUF by prepared surfactants, when ammonium polyphosphate (APP) and expandable graphite (EG) were introduced to provide good flame retardancy. As a result, with just 2.8wt% content of those functional surfactants, hydrophobic and flame-retardant RPUF with water contact angle of 126 °, limiting oxygen index of 25%, compressive strength of 1.3MPa and thermal conductivity of 27mW/mK, were finally obtained, which is ahead of other flame-retardant RPUF reported before. It’s worth noting that, this hydrophobic and flame-retardant RPUF exhibits more stable and durable properties when soaking in HCl solution (2mol/L), NaOH solution (2mol/L), NaCl saturated solution and various solvents (THF and EtOH), or under strong fiction for 100 times and high and low temperature cycling test for 20 times. This would provide a novel and effective strategy to endow RPUF with enhanced and durable flame retardancy, hydrophobicity, compressive strength and thermal insulating performance even under extreme conditions.

Lignin-derived core-shell flame retardants for fire-safety rigid polyurethane (RPU) insulations

How to ensure the fire safety of rigid polyurethane (RPU) insulation materials remains a challenge. Herein, alkali lignin (AL) and 4,4'-diphenylmethane diisocyanate (MDI) were used as raw materials to construct bio-based cross-linked polyurethane structures on the surface of ammonium polyphosphate (APP) to obtain APP@AL flame retardants. APP@AL was combined with expandable graphite (EG) in varying proportions and applied to rigid polyurethane (RPU) foam to modify its flame retardancy and physico-mechanical characteristics. Compared with untreated RPU, the high interfacial compatibility increased the compressive strength of the flame-retardant RPUs by 10.8%, and the thermal insulation coefficient reached 22.8mW·m−1·K−1. The addition of flame retardant for each flame-retardant RPU was 30wt% of the polymethylene polyphenyl isocyanate. Owing to the P/C/O hybridized char layer in the combustion residues and the capture of gas by EG after expansion, APP@AL/EG not only reached the limiting oxygen index (LOI) of 27.1% but reduced the mean heat release rate and smoke release rate by 70.3% and 58.9%, respectively. This work presented a novel approach to designing environmentally friendly flame retardants for RPU foams with enhanced fire safety and superior overall performance. Additionally, it offers a novel strategy for the high-value conversion of lignin.

Caramel doped with aromatic compounds as halogen- and phosphorus-free flame-retardant strategy for wool fabric

The development of halogen- and phosphorus-free flame-retardant strategies is urgently needed in textile industry. In this study, a caramel product doped with aromatic compounds was developed via caramelization and aldol reactions using glucose and p-phthaldialdehyde. The modified caramel (Car@PDA) was subsequently used as a sustainable approach to improve flame retardancy of wool fabric. The flame retardancy, washing durability, heat generation, and flame-retardant mode of action of Car@PDA on wool fabric were investigated. The modified wool fabrics showed excellent flame retardancy, with the limiting oxygen index increasing to 32.5 % and the damaged length decreasing to 10.1 cm, with good self-extinguishing capacity. Car@PDA could combine with wool fibers through Schiff base reaction and electrostatic attraction, so the modified wool fabrics still self-extinguished and met the B1 flame-retardant requirements after 10 washing cycles. The modified wool showed significantly decreased heat release capacity and fire growth rate, suggesting high fire safety. Car@PDA promoted the decomposition of the fabric to form char barrier, thereby achieving an effective flame-retardant effect. In addition, the Car@PDA modification had a minimal effect on the tensile strength and handle of wool fabric. This study provides an innovative way to create bio-based, halogen- and phosphorus-free flame-retardants for protein wool fabrics.

Anti-flammable, anti-fouling, anti-bacterial treatment of cotton fabrics with MOF-based hybrid coatings for highly efficient oil-water separation

A flame-retardant and hydrophobic coating was deposited on the surface of the cotton fabric via a two-step spray deposition technique. Specifically, the coating was composed of flame retardant components (guanidine phosphate) and hydrophobic species (Ti-MOF and bis(3-aminopropyl)-terminated poly(dimethylsiloxane) (PDMS)) and crosslinked with glutaraldehyde. The limiting oxygen index (LOI) of the coated cotton fabrics increased from 18.0 % to 32.0 % (15#) and 26.5 % (15#-Ti-PDMS) relative to that of the original cotton fabric, and the coated cotton fabrics also self-extinguished in the UL-94 flammability test. Compared with that of the original cotton fabric, the PHRR of the coated fabrics was significantly lower, reaching 80 %. The coated cotton fabrics (15# and 15#-Ti-PDMS) had good antibacterial properties against Staphylococcus aureus (S. aureus). In addition, 15#-Ti-PDMS had high hydrophobicity, good washing and abrasion resistance and good water-oil separation performance. Its water contact angle was 146°. The water contact angle remained above 130° after 10 laundering cycles and 50 scratch cycles. Even under strongly acidic and basic conditions, the water-oil separation efficiency of 15#-Ti-PDMS was greater than 99 %, and it was still greater than 90 % after 10 cycles. Therefore, a simple and effective method for preparing flame-retardant, hydrophobic and antibacterial cotton fabrics was developed.

Hierarchical Nano/Micro-Array Structured CuMgAl-LDH/rGO Hybrids for Remarkably Improved Flame Retardancy and Smoke Suppression Performance of Flexible Polyvinyl Chloride.

In this study, we explored the rational integration of layered double hydroxides (LDHs) with reduced graphene oxide (rGO) to create a hierarchical nano/microarray structured CuMgAl-LDH/rGO hybrid aimed at enhancing the flame retardancy and smoke suppression properties of polymer nanocomposites. The results indicated that the limiting oxygen index (LOI) value of the G-CuMgAl/polyvinyl chloride (PVC) composite reached 35.8%, reflecting a 6.4% increase compared to pristine PVC (29.4%), and achieved a UL-94 V-0 rating. Furthermore, in comparison to pristine PVC, the peak heat release rate (PHRR) of the G-CuMgAl/PVC composite was significantly reduced by 40.2%; the total heat release rate (THR) decreased by 24.3%; the maximum average heat release rate (MARHE) diminished by 41.6%; the peak smoke production (PSPR) decreased by 37.8%; the total smoke production (TSP) was reduced by 31.3%; and the average effective heat of combustion (av-EHC) decreased by 15.2%. The enhanced flame retardancy and reduced smoke production can primarily be attributed to the multiple synergistic interactions among the highly dispersed constituents and the nano/microstructures, which effectively impede the transfer of heat, mass, and O2 from various directions while preventing further combustion of the underlying matrix by creating a tortuous path in the condensed phase. Additionally, this study provides a novel perspective on the design and synthesis of structured LDHs/rGO hybrids, with the potential to enhance flame retardancy and smoke suppression properties across a broad spectrum of polymer materials.

Effect of visual lung recruitment manoeuvres guided by trans-oesophageal lung ultrasound on atelectasis after thoracoscopic lobectomy: a randomised, single-blind, prospective study

BackgroundAlthough the incidence of postoperative atelectasis could be reduced using lung recruitment manoeuvres, it remains high. We hypothesised that intraoperative visual lung recruitment guided by trans-oesophageal lung ultrasound would be more effective than the conventional method for managing postoperative atelectasis.MethodsIn this randomised, controlled, prospective study, 84 patients undergoing thoracoscopic lobectomy were recruited from Affiliated Chengdu Fifth People’s Hospital (teaching hospital) in China. Patients were grouped into trans-oesophageal lung ultrasound-guided (Group G, n = 42) and control (Group C, n = 42) groups.MethodsLung recruitment was performed after anaesthesia induction, before chest closure and before the endotracheal tube extubation. In Group C, recruitment pressure was controlled at 30 cm H2O for 10 s (performed thrice); in Group G, the pressure was controlled at 30 cm H2O (performed thrice), and the tidal volume did not exceed 20 ml kg−1 until no atelectasis was detected by trans-oesophageal ultrasound. The primary outcome was lung ultrasound scores measured at the post anaesthesia care unit 30 min after extubation. The secondary outcomes included the oxygenation index (30 min after extubation) and the incidence of atelectasis (30 min after extubation and 3 days after surgery).ResultsThe final analysis included 79 patients. The lung ultrasound score was significantly higher in the control group than in the ultrasound-guided group 30 min after extubation (Group C vs. Group G, 8.6 ± 2.6 vs. 6.5 ± 2.0, P < 0.001). No significant difference in the oxygenation indexes 30 min after extubation was observed between the groups (P = 0.074); however, the incidence of atelectasis 30 min after extubation significantly differed between the two groups (Group C vs. Group G, 57% vs. 33%, P = 0.031). The incidence of atelectasis 3 days after surgery did not significantly differ between the two groups (Group C vs. Group G, 45% vs. 28%, P = 0.122).ConclusionsLung recruitment guided by trans-oesophageal lung ultrasound can reduce lung ultrasound scores and the incidence of atelectasis at the post anaesthesia care unit 30 min after extubation. However, it does not significantly reduce the incidence of atelectasis 3 days after surgery.Trial registrationRegistration number: ChiCTR2200062509. Registered on 10 /8/ 2022.

High rubber elasticity and thermal conductivity in plasticized polyvinyl chloride film with flame retardancy and smoke suppression properties

AbstractFor hydrogenated nitrile‐butadiene rubber (HNBR) modified polyvinyl chloride (PVC), magnesium hydroxide and antimony trioxide are frequently employed as flame retardants. Fume silica is thought to be useful reinforced agent for rubber as well as efficient flame retardant for polymer‐based composites. The plasticized PVC and HNBR blend in this work were combined with three fillers mentioned above to create rubber‐plastic composites that performed well overall, with a notable improvement in combustion. The limiting oxygen index of the composites increased from 23.7% to 33.8% with no droplets falling during combustion, the smoke density rating decreased from 23.8% to 7.9%, and the maximum smoke density dropped from 95.5% to 15.5%. The cone calorimetry test findings revealed that the three fillers simultaneously prevented the emission of smoke and heat from combustion. High thermal conductivity is typically linked to excellent flame retardancy. The thermal conductivity of composites rose from 0.193 to 0.583 W m−1 K−1 with the addition of fillers. Furthermore, the low glass transition temperature and permanent set of improved composites reflect its softness and rubber elasticity. Thermogravimetric analysis was used to examine the thermal stability of the composites in nitrogen and air, and the results indicated the addition of fillers improved the thermal stability.

Diagnostic value of ultrasound for community-acquired pneumonia in children and its correlation with serum PCT level and PCIS.

This study aimed to evaluate the diagnostic value of ultrasound for community-acquired pneumonia (CAP) in children. Clinical information of children diagnosed with CAP and a control group of healthy children was collected, and lung ultrasound detection was performed. The lung ultrasound score (LUS) was assessed, and venous blood samples were collected. Serum indexes, including white blood cell count, were analyzed using an automatic immunoassay analyzer, while serum procalcitonin (PCT) level was measured using an enzyme-linked immunosorbent assay. The pediatric critical illness score (PCIS) was also performed for all subjects. White blood cell count, absolute neutrophil count, and respiratory index were significantly higher in the CAP group than those in the control group, while the oxygenation index was markedly lower. Ultrasound detection results showed that the CAP group exhibited significantly higher detection rates of pleural effusion, interstitial lung changes, lung consolidation, B-lines, air bronchogram signs, and reduced or absent lung sliding signs compared with the control group. In addition, the LUS and PCT levels were markedly higher in the CAP group, while the PCIS was notably lower. Further analysis exhibited that the LUS in the CAP group was significantly positively correlated with PCT levels and negatively correlated with PCIS. The receiver operating characteristic curve indicated that the area under the curve of LUS for diagnosing children with lung infection was 0.841. LUS is closely related to serum PCT level and PCIS. Lung ultrasound detection demonstrates high sensitivity and specificity, indicating its valuable clinical diagnostic utility for CAP in children.

Study on road performance and flame retardant properties of direct-to-plant warm mixing-flame retardant SBS composite modified asphalt

In order to mitigate the current state of the asphalt tunnel fire crisis, this study intends to prepare a novel environmentally friendly direct-to-plant warm mixing-flame retardant SBS composite modified asphalt that will slow down the burning of asphalt itself and reduce the amount of smoke that is produced. This research introduced the preparation process for direct-to-plant SBS modified asphalt. Through conventional performance experiments, flash point and oxygen index tests, and based on DSR and BBR tests, a comparative analysis of ATH and HF-216 flame retardants was conducted. Additionally, the road performance and flame retardant properties of various warm mix types were analyzed by compounding them with flame retardants. The findings indicate that ATH and HF-216 flame retardants can, respectively, raise the softening point by 13 % and 16 %, lower the ductivity by 6 % and 7 %, and decrease the needle penetration of D-SBS by 10 % and 18 %.Both can enhance asphalt's high-temperature characteristics while negatively affecting its low-temperature characteristics. Warm mixing agent and flame retardant can greatly increase the consistency and deformation resistance of direct-to-plant SBS-modified asphalt; however, they also reduce the ductility of the material by 26 %, 16 %, and 12 %, respectively, which will negatively impact its performance at low temperatures. The composite modified asphalt's high temperature stability can be enhanced by compound mixing the three types of warm mixture before and after aging; nevertheless, the fatigue performance declines to varying degrees and the fatigue factor rises by 3535, 3811, and 3889 kPa, respectively. The warm mixture and flame retardant mixture's S value is 82.5 MPa, 33.7 MPa, 13.8 MPa (-12°C), and 187.4 MPa, 90.7 MPa, and 40.6 MPa (-18°C) higher than the D-SBS mixture's, respectively. The low temperature brittleness of D-SBS can be increased by combining a heated mixture with a flame retardant. The burning times of the Marshall and rut plate specimens are shortened by 31, 46, 55, and 86 s, respectively, when compared to the D-SBS combination. The residual stability is raised by 19.2 %, 21.2 %, and 6 %, 10.7 %, respectively, while the mass loss before and after combustion is decreased by 3.9 g, 5.8 g, and 26 g, 32 g, respectively. AH type exhibits superior flame retardant performance than WH type.

Enhancing Flame Retardancy in Epoxy Resin with Clever Self-Assembly Method for Optimizing Interface Interaction via Well-Dispersed Cerium Oxide on Piperazine Pyrophosphate

Developing flame-retardant epoxy resins (EPs) is essential to broaden their industrial applications, as their inherent flammability restricts their widespread use. In this study, commercial cerium oxide (CeO2) nanoparticles were modified with oleic acid and successfully assembled onto the surface of pyrophosphate piperazine (PAPP) through a simple solvophobic effect, constructing an integrated superstructure flame retardant, CeO2@PAPP, with enhanced performance integration. Compared to traditional simple blends, the EP composite with 10 wt% CeO2@PAPP displayed superior flame retardancy, thanks to the more subtle synergistic effects between flame retardant components and their favorable interface interactions. The EP composite achieved a UL-94 V-0 rating and increased the limiting oxygen index (LOI) to 34.2%. Significant reductions of 56.3% in peak heat release rate (PHRR) and 38.2% in total heat release (THR) were observed. Furthermore, total smoke release (TSR), carbon monoxide yield (COPR), and carbon dioxide yield (CO2PR) decreased by 52.2%, 50.2%, and 67.3%, respectively. Through comprehensive and detailed characterization, it was discovered that the assembled integrated CeO2@PAPP flame retardant can perform better in both the gas phase and condensed phase, resulting in superior flame-retardant properties. This study offers an effective strategy for developing highly flame-retardant EPs, thereby expanding their potential applications across various industries.

Synergistic Reinforcing Effect of Hazelnut Shells and Hydrotalcite on Properties of Rigid Polyurethane Foam Composites

Recently, the development of composite materials from agricultural and forestry waste has become an attractive area of research. The use of bio-waste is beneficial for economic and environmental reasons, adapting it to cost effectiveness and environmental sustainability. In the presented study, the possibility of using hazelnut shell (HS) and hydrotalcite (HT) mineral filler was investigated. The effects of fillers in the amount of 10 wt.% on selected properties of polyurethane composites, such as rheological properties (dynamic viscosity, processing times), mechanical properties (compressive strength, flexural strength, hardness), insulating properties (thermal conductivity), and flame-retardant properties (e.g., ignition time, limiting oxygen index, peak heat release), were investigated. Polyurethane foams containing fillers have been shown to have better performance properties compared to unmodified polyurethane foams. For example, the addition of 10 wt% of hydrotalcite filler leads to PU composite foams with improved compression strength (improvement by ~20%), higher flexural strength (increase of ~38%), and comparable thermal conductivity (0.03055 W m–1 K–1 at 20 °C). Moreover, the incorporation of organic fillers has a positive effect on the fire resistance of PU materials. For example, the results from the cone calorimeter test showed that the incorporation of 10 wt% of hydrotalcite filler significantly reduced the peak of the heat release rate (pHRR) by ca. 30% compared with that of unmodified PU foam, and increased the value of the limiting oxygen index from 19.8% to 21.7%.

Diphenylphosphine oxide derivative with a symmetrical structure as an efficient flame retardant for application in epoxy resin

AbstractA fresh phosphorus‐containing fireproofing agent (oxybis(4,1‐phenylene))bis((2,5‐dihydroxyphenyl)(phenyl)phosphine oxide) (ODDPO‐HQ) was synthesized by a simple two‐step reaction. The effect of ODDPO‐HQ on the glass transition temperature (Tg), crosslinking density, thermal stability, fire resistance, dielectric performances, hydrophobicity, and water absorption of epoxy resin (EP) was studied. EP/ODDPO‐HQ containing 1.2 wt% phosphorus not only achieved the vertical burning V‐0 grade with a limited oxygen index of 28.9% but also maintained good thermal stability. Compared to unmodified EP, its Tg value has only decreased by 7.2°C. Detailed studies revealed that the excellent flame resistance of ODDPO‐HQ for epoxies was ascribed to the flame suppression both in the gaseous phase and condensed phase, especially the obvious barrier effect. Although the water uptake of the modified epoxies slightly rose with the content of ODDPO‐HQ caused by the reduction of the crosslinking density within the matrix, it did not adversely affect the properties of the polymer. The modified epoxies showed reduced dielectric constant and dielectric loss values, and the contact angle of EP/ODDPO‐HQ samples increased as the flame retardant content rose, which might be due to the symmetrical structure of ODDPO‐HQ reducing the polarity. Our study presents an easy approach for producing high‐performance epoxies.

Combined effect of sprint interval training and post-exercise blood flow restriction on muscle deoxygenation responses during ramp incremental cycling.

This study investigated the effect of sprint-interval training combined with post-exercise blood flow restriction (i.e., SIT + BFR) on pulmonary gas exchange and microvascular deoxygenation responses during ramp incremental (RI) cycling. Nineteen healthy, untrained males (mean ± SD age: 24 ± 5years; height: 178 ± 6cm; body mass: 77.0 ± 10.7kg) were assigned to receive 4weeks of SIT or SIT + BFR. Before and after the intervention period, each participant completed a RI cycling test for determination of peak oxygen uptake ( ) and the gas exchange threshold (GET) with deoxygenated heme (Δdeoxy[heme]) and tissue oxygenation index (TOI) measured by near-infrared spectroscopy (NIRS) in vastus lateralis (VL) muscle. Relative increased by 7% following both interventions (P ≤ 0.03). SIT + BFR increased peak Δdeoxy[heme] when normalized relative to leg arterial occlusion (PRE: 57.3 ± 13.0 vs. POST: 62.0 ± 13.2%; P = 0.009) whereas there was no significant difference following SIT (PRE: 64.9 ± 14.3 vs. POST: 71.4 ± 11.7%; P = 0.17). Likewise, TOI nadir decreased at exhaustion following SIT + BFR (PRE: 56.9 ± 9.1 vs. POST: 51.4 ± 9.2%; P = 0.002) but not after SIT (PRE: 58.5 ± 7.1 vs. POST: 56.3 ± 8.2%; P = 0.29). The absolute cycling power at the GET increased following SIT + BFR (PRE: 108 ± 13 vs. POST: 125 ± 17 W, P = 0.001) but was not significantly different following SIT (PRE: 112 ± 7 VS. POST: 116 ± 11 W, P = 0.54). The addition of post-exercise BFR to SIT alters the mechanism underlying the enhancement in by increasing the peak rate of muscle fractional O2 extraction in previously untrained males.

Lung Ultrasound Score, Severity of Acute Lung Disease and Prolonged Mechanical Ventilation in Children.

Lung ultrasound may be useful for prognostication of acute lung disease. To assess whether the lung ultrasound score is associated with the severity of lung disease and may predict prolonged invasive mechanical ventilation in critically ill children. Prospective observational multicenter study in children aged 1 month to 18 years who required respiratory support in the intensive care unit. Children with chronic parenchymal lung disease were excluded. The lung ultrasound score was obtained at 12 hours and 48-72 hours from admission. Prolonged invasive mechanical ventilation was defined as >7 consecutive days. Correlation of the lung ultrasound score with oxygenation as well as its prognostic accuracy for prolonged invasive mechanical ventilation were investigated. 538 children were included and 62 (11.5%) required prolonged mechanical ventilation. In these subjects, the lung ultrasound score was higher at 12 [24 (19-26) vs. 8 (3-14); p<0.001] and 48-72 hours [16 (10.5-22.5) vs. 6 (3-11) vs; p<0.001]. At 12 hours the lung ultrasound score correlated with oxygenation index [R2= 0.435 (95% CI: 0.293-0.566), rho coefficient -0.705, p<0.001] and oxygen saturation index [R2 0.499 (95% CI: 0.370-0.613), rho coefficient 0.651, p<0.001p<0.001]. To predict prolonged invasive mechanical ventilation, the lung ultrasound score at 12 hours had a good accuracy [AUROC=0.87 (95% CI: 0.81-0.93)] while its use in a multivariable model had an excellent accuracy both in derivation [AUROC=0.92 (95% CI: 0.89-0.95)] and internal validation [AUROC=0.91 (95% CI: 0.90-0.92)]. In critically ill children, the lung ultrasound score early after admission may predict prolonged invasive mechanical ventilation.

Effects of Anchovy, Mussel, and Shrimp Powders on the Flame Retardancy of Bacterial Cellulose

ABSTRACT This study aims to fabricate bacterial cellulose with improved flame retardancy by applying anchovy, mussel, and shrimp powders. The elemental analysis confirmed that raw marine powders contained nitrogen and sulfur elements which could play important roles in enhancing the flame retardancy of bacterial cellulose. Thermogravimetric analysis revealed the improved thermal stability of bacterial cellulose following entrapping and crosslinking of the marine powders. The fabricated bacterial celluloses with marine powders had similar levels of flame retardancy as that of bacterial cellulose treated with a commercial flame-retardant, sodium metasilicate nonahydrate, which was confirmed by the vertical flammability test and limiting oxygen index. The char morphology analysis revealed intumescent char on the surface of the samples, confirming the effect of marine powders on the flame retardancy of bacterial cellulose. Moreover, the marine powders were entrapped and crosslinked with bacterial cellulose nanostructures, and the chemical and crystalline structures of bacterial cellulose were retained. This study proposes an efficient method to improve the flame retardancy of bacterial cellulose by introducing marine powders via the combined entrapment and crosslinking method.

Char, gas, and action: Transfer of the flame-retardant modes of action in epoxy resins and their fiber-reinforced composites

Flame retardants are often developed for epoxy resins and then transferred into their fiber-reinforced composites with uncertain results. Understanding this transfer in detail represents a critical scientific challenge. This study systematically compares epoxy resins with their glass-fiber reinforced composites, focusing on bisphenol A diglycidyl ether with the hardener dicyandiamide, the flame retardants melamine polyphosphate, ammonium polyphosphate, and silane ammonium polyphosphate, along with inorganic silicate. The research investigates changes in pyrolysis (thermogravimetry), flammability (UL 94, limiting oxygen index), and fire behavior (cone calorimeter) while also examining the flame-retardant modes of action and overall fire performance. The findings reveal that alterations in the amount of fuel, thermal properties, melt flow, and protective layer significantly impact ignition, flammability, and fire load, with a critical reduction in carbonaceous char within the composites preventing intumescence. This study quantifies the effects and provides a fundamental scientific understanding of the complex transfer process of flame retardants from resins to composites, offering essential insights that are of major importance for developing more effective flame-retardant materials.

Preparation and Characterization of Glucose-Based Self-Blowing Non-Isocyanate Polyurethane (NIPU) Foams with Different Acid Catalysts.

The preparation and application of non-isocyanate polyurethane (NIPU) from biomass raw materials as a substitute for traditional polyurethane (PU) has recently become a research hot topic as it avoids the toxicity and moisture sensitivity of isocyanate-based PU. In the work presented here, self-blowing GNIPU non-isocyanate polyurethane (NIPU) rigid foams were prepared at room temperature, based on glucose, with acids as catalysts and glutaraldehyde as a cross-linker. The effects of different acids and glutaraldehyde addition on foam morphology and properties were investigated. The water absorption, compressive resistance, fire resistance, and limiting oxygen index (LOI) were tested to evaluate the relevant properties of the foams, and scanning electron microscopy (SEM) was used to observe the foams' cell structure. The results show that all these foams have a similar apparent density, while their 24 h water absorption is different. The foam prepared with phosphoric acid as a catalyst presented a better compressive strength compared to the other types prepared with different catalysts when above 65% compression. It also presents the best fire resistance with an LOI value of 24.3% (great than 22%), indicating that it possesses a good level of flame retardancy. Thermogravimetric analysis also showed that phosphoric acid catalysis slightly improved the GNIPU foams' thermal stability. This is mainly due to the flame-retardant effect of the phosphate ion. In addition, scanning electron microscopy (SEM) results showed that all the GNIPU foams exhibited similar open-cell morphologies with the cell pore sizes mainly distributed in the 200-250 μm range.

Co Hybrids modified piperazine pyrophosphate towards efficient flame retardancy, smoke suppression, and high mechanical properties of styrenic thermoplastic elastomer

The highly flammable nature of thermoplastic elastomers (TPE) results in poor fire safety performance. The large addition of flame retardants leads to a significant decrease in mechanical properties. To solve above challenges, we design a multilayer core-shell flame retardant, piperazine pyrophosphate@ tannic acid@ Co amorphous hybrids (PAPP@TA@Co-2-MIM) and add it to TPE to enhance the fire safety and mechanical performance simultaneously. It was found that the addition of 32 wt% PAPP@TA@Co-2-MIM achieved a UL-94 V-0 rating of TPE composites, with a limiting oxygen index of 27 %. Compared to pure TPE, the peak heat release rate, total heat release, total smoke production, and peak CO release rate of TPE/PAPP@TA@Co-2-MIM were reduced by 79.8 %, 37.1 %, 42.9 %, and 82.5 %, respectively, effectively suppressing the release of heat, smoke, and toxic gases. Besides, the flame-retardant mechanism was also explained. In terms of mechanical performance, benefiting by the bridging effect of the core-shell structure, the tensile strength of TPE/PAPP@TA@Co-2-MIM increased by 52.7 %, compared to TPE/PAPP. This study designed a TPE composite material that showed good thermal stability, high fire safety performance and enhanced mechanical properties.