Polybenzoxazine Resins with Cellulose Phosphide: Preparation, Flame Retardancy and Mechanisms

Phosphated cellulose (PCF) was synthesized based on urea, phosphated acid and cellulose. The structure of the PCF was confirmed by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy coupled with the Energy Dispersive Spectrometer (SEM-EDS). Benzoxazine (Ba)/PCF hybrid materials were fabricated and thermally cured to prepare polybenzoxazine composites (PBa/PCF). The effects of PCF on the curing temperature of Ba were analyzed through differential scanning calorimetry (DSC). The thermogravimetric (TGA) results demonstrated an increased char residue of 50% for the PBa composites incorporating PCF-5% compared with the pure PBa. The peak heat release rate (PHRR) and total heat release (THR) values of the PBa/PCF-5% composites clearly decreased by 58.1% and 16.5% compared to those of the pristine PBa. The smoke released from the PBa/PCF system significantly reduced with the loading of PCF. Moreover, the limited oxygen index (LOI) and vertical burning test level (UL-94) of PBa/PCF-5% reached up to 31 and V0. The flame retardant mechanism of the PCF in the PBa matrix was investigated TG-FTIR and char residues analysis. Finally, the dynamical mechanical analysis (DMA) results demonstrated that the Tg of the PBa/PCF composites was approximately 230 °C, which does not affect further applications of PBa composites.

Transparent low-flammability epoxy resins using a benzoguanamine-based DOPO derivative

We successfully prepared a highly effective flame-retardant additive called hsalbenzoguanamine phosphaphenanthrene (HDPD) through salicylaldehyde and nitrogen-rich benzoguanamine. The introduction of HDPD into epoxy resin (EP) sharply enhanced the flame retardancy of EP/HDPD thermosets. The introduction of 6 wt% HDPD into EP succeeded in reaching the V-0 rating. Limited oxygen index results revealed the high flame-retarding performance of HDPD. Cone calorimeter test data revealed that heat and smoke released from EP/6 wt% HDPD thermoset were significantly restrained. In addition, EP/6 wt% HDPD thermoset demonstrated excellent transmittance and mechanical strength. The transmittance of EP/6 wt% HDPD was assessed from 520 to 800 nm. The results showed that transmittance of EP/6 wt% HDPD were nearly 90% of the control group.

Durable and High-efficiency Casein-derived Phosphorus-nitrogen-rich Flame Retardants for Cotton Fabrics

A casein derivative (CADP) was synthesized using casein, which is bifunctional containing both –P=O(O-NH4+)2 reactive groups and -P(=O)-O-C- groups, and the durable flame-retardant cotton fabrics were successfully prepared by CADP. The –P=O(O-NH4+)2 reactive groups allowed CADP to be firmly grafted onto cellulose. The –P(=O)-O-C- groups made flame-retardant cotton fabrics more resistant to soaping and improved its durability. The modification by 40% CADP increased the limited oxygen index value (LOI) of cotton fabric from 17.4% to 41.6%, which maintained at 26.4% after 50 cycles of home machine washes. The results of TG, TG-FTIR and SEM indicated that CADP increased the condensed components and decreased the flammable gaseous compounds, resulting the positive effect on char formation of cellulose. The whiteness and tensile strength of cotton fabrics were retained well after modification, and the treated cotton fabrics didn’t have skin irritation.

The cryo-EM structure of the bd oxidase from M. tuberculosis reveals a unique structural framework and enables rational drug design to combat TB

New drugs are urgently needed to combat the global TB epidemic. Targeting simultaneously multiple respiratory enzyme complexes of Mycobacterium tuberculosis is regarded as one of the most effective treatment options to shorten drug administration regimes, and reduce the opportunity for the emergence of drug resistance. During infection and proliferation, the cytochrome bd oxidase plays a crucial role for mycobacterial pathophysiology by maintaining aerobic respiration at limited oxygen concentrations. Here, we present the cryo-EM structure of the cytochrome bd oxidase from M. tuberculosis at 2.5 Å. In conjunction with atomistic molecular dynamics (MD) simulation studies we discovered a previously unknown MK-9-binding site, as well as a unique disulfide bond within the Q-loop domain that defines an inactive conformation of the canonical quinol oxidation site in Actinobacteria. Our detailed insights into the long-sought atomic framework of the cytochrome bd oxidase from M. tuberculosis will form the basis for the design of highly specific drugs to act on this enzyme.

Investigating the Effect of Aluminum Diethylphosphinate on Thermal Stability, Flame Retardancy, and Mechanical Properties of Poly(butylene succinate)

Poly(butylene succinate) is one of the most promising biodegradable polymers, but its applications are limited by poor flame retardancy. In this work, poly(butylene succinate)/diethylphosphinate (PBS/AlPi) composites were fabricated to investigate the effect of AlPi on their thermal stability, flame retardancy, and mechanical properties. It was found that the high content of AlPi decreased the thermal stability of PBS, and the decrease became stronger under the air atmosphere. When the content of AlPi reached 25wt%, the flame retardancy was improved with limited oxygen index (LOI) of 29.5%, V0 rating in UL-94 vertical burning test, and 49.3% reduction on the peak of heat release rate (PHRR) in cone calorimeter test. Meanwhile, the addition of AlPi could improve the mechanical properties of PBS with high tensile strength and Young’s modulus, which was ascribed to the compatible effect of maleic anhydride-grafted poly(butylene succinate) (PBS-g-MA) with good filler dispersion and strong matrix-particles interaction. Thus, the AlPi was an effective flame retardant to PBS, so that PBS/AlPi composites displayed excellent flame retardancy without seriously sacrificing other comprehensive performances.

Polylactic acid flame-retarded by nano-compound of form II ammonium polyphosphate with montmorillonite

It is reported a convenient method to obtain flame-retardant polylactic acid composite by adding low amount of crystal form II ammonium polyphosphate (APP-II) or nano-compound of crystal form II ammonium polyphosphate with calcium-based montmorillonite. The structures and thermal properties of the crystal form II ammonium polyphosphate and crystal form II ammonium polyphosphate with calcium-based montmorillonite were characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, and thermogravimetric analysis. Crystallography and morphologies of the polylactic acid and its composites with the crystal form II ammonium polyphosphate and crystal form II ammonium polyphosphate with calcium-based montmorillonite were measured through differential scanning calorimeter and scanning electron microscopy. In flame retardancy of the polylactic acid composites, the 5 wt% crystal form II ammonium polyphosphate could make the polylactic acid achieve the UL-94 vertical burning V-0 rating and limited oxygen index 27.3%. When using crystal form II ammonium polyphosphate with calcium-based montmorillonite in flame-retarding polylactic acid, only 3 wt% nano-compound can result in the same V-0 rating level and the limited oxygen index of 28.0%. Meanwhile, polylactic acid with crystal form II ammonium polyphosphate or crystal form II ammonium polyphosphate with calcium-based montmorillonite still keeps the good mechanical properties. The developed systems are environmentally friendly and highly effective flame retarding, which show a promising future in practical large-scale polylactic acid application.

The Disappearance of Coal Seams Recorded in Associated Gangue Rocks in the SW Part of the Upper Silesian Coal Basin, Poland

Coal seams in the Upper Silesian Coal Basin vanish within the Carboniferous Upper Silesian Sandstone Series and below an unconformity marking the Carboniferous top surface. Changes in the geochemical, mineralogical, petrological and palynological characteristics of gangue rocks associated with the vanished seams record what happened. The observed changes could have been caused by (1) coal-seam paleofire, (2) peat combustion, (3) igneous intrusion, (4) metasomatism and/or (5) weathering. Multifaceted research on samples collected at the Jas-Mos mining area, a part of the operating Jastrzębie-Bzie Coal Mine that are representative of different geological settings in the northern and southern parts of the mining area, point to intra-deposit paleofire as the most plausible reason for the disappearance. Biomarkers enabled recognition of differences in heating duration and oxygen access. Coal seams in the south burned quickly with abundant oxygen supply. Seams in the north pyrolyzed for an extended time under conditions of limited oxygen. Though other methods used proved less sensitive, all confirmed low (100–150 °C) paleotemperature heating. Overall, the reason for the local disappearance of the coal seams, making their exploitation difficult and unprofitable, can be assigned to a variety of different processes in a complex overlapping history of variable weathering, heating due to local endogenic fires and, probably, earlier peat combustion.

TELEMEDICINE STRATEGY CONCEPTS IN HANDLING COVID-19 IN INDONESIA IN 2021

Indonesia is one of the countries where the spread of COVID-19 is one of the highest in the world with an average daily from June to July 2021 of 14,000 people who are positive for COVID-19, which so far has touched 2.3 million people with a cure rate of 84% and a mortality rate of 2.6%. The increase in the number of people who are positive for COVID-19 has made the government's burden even heavier. The most crucial problem is the availability of beds, at the national level the hospital occupancy rate has been above 80% so that many hospitals are no longer accepting COVID-19 patients, limited oxygen and health workers are obstacles that must be addressed as soon as possible. The government's policy of implementing an emergency PSBB on the island of Java as a solution in reducing the positive Covid-19 has been effective, although there are still many weaknesses that must be evaluated. Emergency policies to deal with covid-19 patients who cannot be handled by hospitals using the concept of telemedicine with patients being treated at home by being provided with online consultation facilities, drugs ordered and delivered for free through online media, this concept is considered the most effective in an emergency pandemic case. this covid-19.

A superhydrophobic and flame-retardant cotton fabric fabricated by an eco-friendly assembling method

A novel eco-friendly and durable superhydrophobic and flame-retardant cotton fabric with fluorine-free, halogen-free was prepared via step-by-step dip-coating and spraying technology. At first, common cotton fabric was impregnated in the flame-retardant ethoxysilane-terminated phosphate polyurethane. Afterwards, methanol mixture containing silica nanoparticles, methyl triethoxysilane, and dihydroxy-terminated polydimethylsiloxane was sprayed on the surface of the cotton fabric. Finally, a flame-retardant cotton fabric with micro-nano rough surface and low surface energy was formed. The resulting superhydrophobic and flame-retardant cotton fabric exhibited superamphiphobicity with the contact angle and sliding angle of 160° and 6°, respectively, while flame retardancy with limited oxygen index of 28.1%. and flame self-extinguishing. Furthermore, this superhydrophobic and flame-retardant cotton fabric showed robust superhydrophobicity and flame-retardancy after undergoing 1000 cycles of abrasion, 60 min of ultrasonic washing and 50 standard machine washing cycles, in sequence, indicating its potential as a multifunctional protective textile fabric. Additionally, the method proposed in this study can effectively solve durability and environmental problems currently faced by the coated fabric with superhydrophobicity and flame-retardancy.