Phosphamide-Based Washing-Durable Flame Retardant for Cotton Fabrics.

A formaldehyde-free reactive flame retardant, an ammonium salt of triethylenetetramine phosphoryl dimethyl ester phosphamide phosphoric acid (ATPEPDPA), was synthesized and characterized using nuclear magnetic resonance (NMR). Fourier transform infrared spectroscopy test (FT-IR), durability test and scanning electron microscopy (SEM) results suggested that ATPEPDPA was successfully grafted on cotton fabrics through a -N-P(=O)-O-C covalent bond. Moreover, the limiting oxygen index (LOI) value of 20 wt% ATPEPDPA-treated cotton was 44.6%, which met stringent washing standard after 50 laundering cycles (LCs). The high washing resistance of the ATPEPDPA-treated cotton was due to the p-π conjugation between the N atom and the P(=O) group in the flame-retardant molecule, which strengthened the stability of the -N-P(=O)-O-C bonds between ATPEPDPA and cellulose, and the -N-P(=O)-(O-CH3)2 groups in the ATPEPDPA. The cone calorimetric test showed that the treated cotton had excellent flame retardance. In addition, the TG and TG-IR tests suggested that ATPEPDPA performed a condensed flame retardance mechanism. Furthermore, the physical properties and hand feel of the treated cotton were well maintained. These results suggested that introducing -N-P(=O)-(O-CH3)2 and -N-P(=O)-(ONH4)2 groups into ATPEPDPA could significantly increase the fire resistance and durability of cotton fabrics.

Synthesis and evaluation of an eco-friendly and durable flame-retardant cotton fabrics based on a high-phosphorous-content.

Cotton fabrics are extremely flammable. Therefore, ammonium salt of dipentaerythritol hexaphosphoric acid (ADPHPA), a novel reactive phosphorus flame retardant without halogen and formaldehyde, was synthesized by solvent-free synthesis method. Surface chemical graft modification was chosen to introduce flame retardant, imparting its flame retardancy and washability. SEM indicated that ADPHPA entered the interior of cotton fiber, which was grafted with OH of control cotton fabrics (CCF) by forming POC covalent bonds to obtain treated cotton fabrics (TCF). There were no apparent differences in the fiber morphology and crystal structure after treatment according to SEM and XRD analysis. TG analysis demonstrated that the decomposition process of TCF was changed compared with CCF, while lower heat release rate and total heat release of TCF indicated its combustion efficiency was also reduced based on cone calorimetry test. Meanwhile, in the durability test, TCF had undergone 50 laundering cycles (LCs) in accordance with AATCC-61-2013 3A standard and had a short vertical combustion charcoal length, which were able to be regard as durable flame-retardant fabrics. The mechanical properties of TCF decreased to a degree, but did not affect the actual use of cotton fabrics. Taken as a whole, ADPHPA has research significance and development potential as a durable phosphorus-based flame retardant.

Iron Phosphate Nanozyme-Hydrogel with Multienzyme-like Activity for Efficient Bacterial Sterilization.

Pathogenic bacteria infections have posed a threat to human health worldwide. Nanomaterials with natural enzymatic activity provide an opportunity for the development of new antibacterial pathways. We successfully constructed iron phosphate nanozyme-hydrogel (FePO4-HG) with the traits of positive charge and macropores. Interestingly, FePO4-HG displayed not only peroxidase-like activity under acidic bacterial infectious microenvironment but also superoxide dismutase-catalase-like synergistic effects in neutral or weak alkaline conditions, thus protecting normal tissues from the peroxidase-like protocol with exogenous H2O2 damage. Furthermore, the positive charge and macropore structure of FePO4-HG could capture and restrict bacteria in the range of ROS destruction. Obviously, FePO4-HG exhibited excellent antibacterial ability against MRSA and AREC with the assistance of H2O2. Significantly, the FePO4-HG + H2O2 system could efficiently disrupt the bacterial biofilm formation and facilitate the glutathione oxidation process to rapid bacterial death with low cytotoxicity. Moreover, FePO4-HG was unsusceptible to bacterial resistance development in MRSA. Animal experiments showed that the FePO4-HG + H2O2 group could efficiently eliminate the MRSA infection and present excellent wound healing without inflammation and tissue adhesions. With further development and optimization, FePO4-HG has great potential as a new class of antibacterial agents to fight antibiotic-resistant pathogens.

Evaluating public organization performance under extreme weather events: Does organizational adaptive capacity matter?

The study examines the impacts of extreme weather events on public organization performance. In response to the growing call for adaptive capacity development amid a worsening climate, it pays particular attention to the effects of organizational adaptive capacity. Three components of an organization's adaptive capacity are investigated: formal institutions, organizational slack and contracting out (inverse of capacity). We focus on organizations' technical efficiency as a key performance indicator. Using a sample of 108 bus transit system in the U.S. Northeast and Midwest from 2008 to 2017, the analysis applies the Battese and Coelli (1995) specification for stochastic frontier analysis (SFA) with panel data. A general model is estimated to incorporate the heterogeneity in both the level and efficiency of output. The results confirm the efficacy of organizational adaptive capacity to enhance efficiency amid extreme weather. Specifically, higher levels of organizational slack or lower levels of contracting out can boost technical efficiency under extreme weather. Formal institutions, while temporarily compromising technical efficiency, holds potential for salient efficiency gains in the long run. The conclusion ends with a discussion on the theoretical and practical implications of this study.

An eco-friendly NP flame retardant for durable flame-retardant treatment of cotton fabric.

A halogen-free, formaldehyde-free, efficient, durable, NP flame retardant, the ammonium salt of meglumine phosphoric ester acid (ASMPEA), was prepared. The Fourier-transform infrared spectroscopy (FTIR) and nuclear magnetic resonance spectroscopy (1H NMR, 13C NMR, and 31P NMR) results indicated that ASMPEA was grafted onto cotton fibers by P-O-C covalent bonds. The LOI value of 30 wt% ASMPEA-treated cotton fabric was 40.2%, and after 50 laundering cycles (LCs), the LOI value decreased to 29.4%, indicating that the cotton fibers treated with ASMPEA were endowed with excellent durable flame retardancy. Thermogravimetry (TG), cone calorimetry, and vertical flammability test results showed that ASMPEA-treated cotton decomposed into phosphoric acid or polyphosphoric acid during combustion, which promoted the thermal degradation and charring of treated cotton fabrics and hindered the spread of flames. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive spectrometry (EDS) verified that ASMPEA infiltrated the cotton fiber without obviously affecting its surface morphology or crystal structure; however, the mechanical properties of the treated cotton fabric decreased slightly. These results confirm that ASMPEA achieved excellent durable flame retardancy when used to coat cotton fabric.

Facile, one-pot, formaldehyde-free synthesis of reactive NP flame retardant for a biomolecule of cotton.

The NP flame retardant ammonium salt of hydroxyethyl hexahydrotristriazine-triphosphoric acid (AHTTPA) was prepared by a one-pot synthesis method under formaldehyde-free and solvent-free conditions. The AHTTPA was finished on the biomolecule of cotton by using the dip-roll-bake method. Nuclear magnetic resonance (NMR 1H, 13C, and 31P) demonstrated that AHTTPA was successfully synthesized. The flame retardancy of AHTTPA-treated cotton was studied by limiting oxygen index (LOI), vertical flaming test (VFT), scanning electron microscopy (SEM), and cone calorimetry (CC). The results from these tests indicate that AHTTPA-treated cotton exhibited favorable flame retardancy and durability (the LOI value of 40%-treated cotton after 50 laundering cycles (LCs) was 29.8%), the flame was immediately extinguished after removal from the treated cotton, no smoldering or continued burning, the burned part formed a complete carbon frame and generally maintained its original morphology, the peak heat release rate (PHRR) and total heat release (THR) of AHTTPA-treated cotton fabric were significantly lower than pure cotton. Thermogravimetric analysis (TGA) results showed that AHTTPA improved the thermal stability of cotton. The breaking strength and softness of AHTTPA-treated cotton was also retained.

Straightforward one-step solvent-free synthesis of the flame retardant for cotton with excellent efficiency and durability.

A flame retardant, ammonium salt of 1-hydroxyethylidene-1,1-diphosphonic acid (AHEDPA), was synthesized by a facile one-step methodology and was proven to have achieved remarkable improved flame retardancy of cotton with exceptional durability because AHEDPA with functional groups PO-(NH4+)2 could react with OH of cellulose to form new POC bonds characterized by Fourier transform infrared (FT-IR) spectra, which further verify that AHEDPA was chemically bound to cotton instead of as additive or mixing into polymer. Combustion behaviors of the control and treated cotton were assessed by cone calorimetry, vertical flammability and limiting oxygen index (LOI) tests. The cone calorimetry results display that the peak heat release rate (PHRR) and total heat release (THR) of cotton fabric treated by 30% AHEDPA were reduced up to 95% and 68%, respectively, compared with those of control cotton. No after-flame and after-glow phenomena for treated cotton were observed in vertical flammable test. LOI test evinces that the cotton fabric treated with 30-40 % AHEDPA could be used as a durable flame retardant fabric with a LOI value of 26.2-29.5% after 50 laundering cycles. Thermogravimetric (TG) data both in nitrogen and in air atmosphere reveal that the AHEDPA treated cotton notably increased the char yield by catalyzing dehydration of cellulose, thus protecting the underlying matrix from heat and fuel. The efficient and durable flame retardant for the AHEDPA by the one-step synthesis method has great development prospects in industrial.

What drives public transit organizations in the United States to adapt to extreme weather events?

Extreme weather events often disrupt the operation of public transit systems, and challenge the capacity of transit agencies to effectively respond to them. In this paper, we draw upon a recent nationwide survey of 273 public transit agencies in metropolitan regions across the United States to understand the factors that influence their scope of adaptation to anticipated climate risks. We find that a transit agency undertakes more adaptation measures when transit officials perceive greater risks and greater adaptive capacity of the agency, or when it experiences more severe extreme weather events. We also show that local institutional environment, in particular, political ideology, affects the scope of transit adaptation activities. Transit agencies that operate in more politically liberal counties tend to engage in more adaptation actions, while the effect of state-level ideology depends on the level of perceived influence from state governments.

A concise water-solvent synthesis of highly effective, durable, and eco-friendly flame-retardant coating on cotton fabrics.

A new halogen-free and formaldehyde-free ammonium salt of melamine hexa(methylphosphonic acid) (AMHMPA) was facilely synthesized as flame retardant (FR) material under water-solvent and low temperature condition to counter inflammable cotton fabric fire hazard. The reactive PO(NH4)2 and PO(OH)2 groups from AMHMPA reacted with cotton reactive OH groups to form POC bonds. A layer of AMHMPA was coated onto the treated-cotton surface, and a carbon skeleton was formed after combustion. The char residue percentages of the treated-cotton fabrics and untreated fabric were 38.5 and 3.6% at 600 °C, respectively. The phosphorus contents for the control, treated-cotton and burned-cotton were 0, 37.499 and 24.896%, respectively. The LOIs of cotton treated with 30-90 g/L AMHMPA reached 32.0-43.0%. After 50 laundering cycles (LCs), the LOIs still maintained 26.0-33.4%. AMHMPA-treated cotton had no cytotoxicity towards the environment and humans. These results demonstrated that AMHMPA-treated cotton exhibited eco-friendly, outstanding durability and excellent flame retardancy. TG-IR and cone calorimeter results confirmed AMHMPA condensation phase flame retardant mechanism.

A plant-based reactive ammonium phytate for use as a flame-retardant for cotton fabric.

A plant-based non-formaldehyde flame retardant containing high phosphorus ammonium phytate (APA) was synthesized for cotton fabric. The char length of treated cotton sample decreased to 31mm from the original 300mm. The LOI value of finished cotton fabric was as high as 43.2%, and after 30 laundering cycles, it still remained 30.5%, suggesting that APA could be used as an effective semi-durable flame retardant. The TG analysis in air demonstrated that the thermal oxidation stability of treated fabric was significantly improved. Cone calorimetry results showed that the peak heat release rate and total heat release of treated sample reduced obviously comparing with that of control sample. The SEM morphologies suggested that the APA molecule penetrated into the inner space of cotton fibers. FTIR spectra implied the APA molecule grafted onto cotton fibers. Then, the effective flame retardant APA has significant potential in practical application.

Durable grafting of silkworm pupa protein onto the surface of polyethylene terephthalate fibers.

In this paper, reactive -NH2 groups (8.36×10(-6)mol/g fabric) were introduced to the surface of polyethylene terephthalate (PET) fabrics by a nitration and reduction method, and epoxy groups were introduced to silkworm pupa protein (SPP) by reaction with epoxy chloropropane. PET-SPP composite fabrics were then prepared by reaction of these two precursors. The results showed that the SPP was firmly grafted onto the PET fabric surface and that the hydrophilicity of the fabric was markedly improved by the grafting of SPP. SEM images revealed a layer of substance covering the surface of the PET fibers, and XPS investigation showed that the nitrogen content of the PET-SPP fabric was higher than that of the original PET fabric (2.32% vs 0%). ATR-FTIR adsorption bands at 1653 and 1543cm(-1) suggested the successful grafting of SPP onto the PET fabric surface. The DSC and TG of the PET fibers demonstrated that the thermal stability of the original PET fibers was maintained well by the SPP-grafted PET fibers. The breaking strength, bending rigidity, air permeability, and crease recovery angle of the original PET fabric were also retained by the SPP-grafted PET fabric.

Study of conformation and thermodynamics of α-amylase interaction with ethylene in vitro.

In this article, the conformation and thermodynamics of α-amylase interaction with ethylene in vitro were investigated. The ultraviolet (UV) absorption showed a strong peak of α-amylase treated with 6.04, 29.32 and 262.11µmolL(-1) ethylene appears at ~222nm and a weak peak at 278nm blue-shifted 1nm. Circular dichroism (CD) spectra indicated that the conformations of α-amylase treated with 29.32 and 262.11µmolL(-1) ethylene were obviously changed in which α-helix content were decreased by 20 and 31% respectively, and ß-sheet, ß-turn and random coil contents were increased by contrast. Fluorescence spectra suggested that the peak intensities of α-amylase at 342nm were obviously increased with the ethylene increase from 6.04 to 525.75µmolL(-1) and more than control group. The binding constants K between ethylene and α-amylase were 3.318×10(6), 4.407×10(6) and 5.125×10(6)Lmol(-1) at 288, 298 and 308K, respectively. And the calculated values of ΔH(0) and ΔS(0) are positive, which suggests that the interaction between ethylene and α-amylase is an endothermic reaction. The negative ΔG(0) values implied that the direct effect of ethylene on α-amylase conformation was spontaneous. The possible reason is that ethylene molecules were easily embedded into the interior of α-amylase in term of the hydrophobic force between α-amylase and ethylene, causing the conformation and thermodynamics changes of α-amylase.