Green Sorbitol- and Isosorbide-Based Flame Retardants for Cotton Fabrics

Flame retardancy is often required in various textile applications. Halogenated flame retardants (FR) are commonly used since they have good FR performance. Several of these components are listed under REACH. Halogen-free FR compounds have been developed as alternatives. So far, not many biobased FR have made it to the market and are being applied in the textile sector, leaving great opportunities since biobased products are experiencing a renaissance. In this study, renewable FR based on sorbitol and isosorbide were synthesised. The reaction was performed in the melt. The resulting biobased FR were characterised via FT-IR, thermogravimetric analysis (TGA) and X-ray fluorescence (XRF). Cotton fabrics functionalized with the developed biobased FR passed ISO 15025 FR test. After washing, the FR properties of the fabrics decreased (longer afterflame and afterglow time) but still complied with ISO 15025, indicating the biobased FR were semi-permanent. The amount of residue of modified sorbitol and isosorbide measured at 600°C in air was 31% and 27%, respectively. Cotton treated with biobased modified FR showed no ignition during cone calorimetry experiments, indicating a flame retardancy. Furthermore, a charring of the FR containing samples was observed by means of cone calorimetry and TGA measurements.

Electrospun PU/MgO/Ag Nanofibers for Antibacterial Activity and Flame Retardency

Antibacterial activity and fire retardation are equally desired for protective clothing. For achieving this, AgNP and MgO are independently researched as nanofillers in Polyurethane based electrospun nanofibers and their synergistic effect is scarcely addressed. This article reports synthesis and characterization of MgO of 70.01 nm and AgNP of 51 to 76 nm by solution combustion and hydrothermal routes respectively and their incorporation in electrospinning of Polyurethane. Flow rate 1 ml/hr, applied voltage 13 kV, tip to collector distance 15 cm were adopted for the electrospinning. Nanofibers of 65 nm were obtained for PU/MgO (3 wt. %) and 106 nm for PU/MgO (3 wt. %)/Ag (1 wt. %). Addition of MgO increased the melting point, after flame time and afterglow time. Incorporation of AgNP improved antibacterial activity. PU/MgO/Ag (2 wt. %) exhibited zone of inhibition of 2.1 cm and 3 cm against E. Coli and S. Aureus, respectively.

High Performance of Simple Organic Phosphorescence Host-Guest Materials

<p><b>The study of purely organic room-temperature phosphorescence (RTP) has drawn </b><b>increasing attention </b><b>because of its considerable theoretical research and practical application </b><b>value</b><b>. Currently, organic RTP materials with both high efficiency (<i>Ф</i>_P > 20%) and a long lifetime (<i>τ</i>_P > 10 s) in air are still </b><b>scarce due to</b><b> the lack of related design guidance. Here, we </b><b>report</b><b> a new strategy to increase the phosphorescence performance of organic materials by integrating the RTP host and RTP guest in one doping system to form </b><b>a </b><b>triplet exciplex. With these materials, the high-contrast </b><b>labelling</b><b> of tumours in living mice and encrypted patterns in thermal printing are both successfully realized for the first time</b><b> by</b><b> taking </b><b>advantage of both</b><b> the long afterglow time (up to 25 min in aqueous media) and high phosphorescence efficiency (43%).</b></p>

High Performance of Simple Organic Phosphorescence Host-Guest Materials

<p><b>The study of purely organic room-temperature phosphorescence (RTP) has drawn </b><b>increasing attention </b><b>because of its considerable theoretical research and practical application </b><b>value</b><b>. Currently, organic RTP materials with both high efficiency (<i>Ф</i>_P > 20%) and a long lifetime (<i>τ</i>_P > 10 s) in air are still </b><b>scarce due to</b><b> the lack of related design guidance. Here, we </b><b>report</b><b> a new strategy to increase the phosphorescence performance of organic materials by integrating the RTP host and RTP guest in one doping system to form </b><b>a </b><b>triplet exciplex. With these materials, the high-contrast </b><b>labelling</b><b> of tumours in living mice and encrypted patterns in thermal printing are both successfully realized for the first time</b><b> by</b><b> taking </b><b>advantage of both</b><b> the long afterglow time (up to 25 min in aqueous media) and high phosphorescence efficiency (43%).</b></p>

Correlations of Major Flame Characteristics of Some Fire Tolerant Trees in South-East Nigeria by Coefficient of Determination (R2)

Background: Bush fire is a common hazard in South East-Nigeria as in other parts of the country during the harmattan. Every year, thousands of hectares of forests as well as suburban lands are severely burnt. These forest fires have been catastrophic, destroying large areas of tropical rain forests and in most cases have claimed many lives and destroyed properties worth millions of naira. However, some of these trees identified by local people and named by taxonomists as Daniellia oliveri, Anacadium occidentale, Vitex doniana, Lonchocarpus griffonianus, Gmelina arborea, Nauclea latifolia, Tectona grandis, Mangifera indica, Delonix regia, Newbouldia laevis, Azadirachta indica, Dialium guineense, Terminalia superba, Manilkara obovata and Irvingia gabonensis have proven to be fire tolerant. Aim: The aim is to establish correlations among the physical properties (wood density and moisture content) and flame characteristics (ignition time, flame propagation rate, flame duration, afterglow time, ash formation and limiting oxygen index) of these fire tolerant trees. Study Design: An item structured instrument was developed by the researchers which reflected the six points modified Likert scale of strongly agree, agree, somewhat agree, somewhat disagree, disagree, strongly disagree and used to elicit information from the respondents who were mainly seasoned wood dealers of above 60 years of age. Analysis of Variance (ANOVA) was the major tool of analysis used to establish whether the tree species tolerates fire or not while correlation of the parameters was achieved by the application of R2. Place and Duration of Study: Determination of both the physical properties and flame characteristics of the tree species was done at the Research Laboratory of the Department of Pure and Industrial Chemistry, Nnamdi Azikiwe University, Awka between June, 2018 and April, 2019. Methodology: The physical properties of the tree species as well as their flame characteristics were carried out using their standard methods. Results: The values for these parameters vary among the tree species. Correlation among the parameters indicates a determination coefficient range from 0.000 to 0.637. Conclusion: There are highly significant correlations between wood density and both ignition time and flame propagation rate as well as wood density and limiting oxygen index. There is also strong correlation between ignition time and both flame propagation rate and limiting oxygen index. Afterglow time depends on limiting oxygen index and vice versa.

A Flame-Retardant Phytic-Acid-Based LbL-Coating for Cotton Using Polyvinylamine

Phytic acid (PA), as a natural source of phosphorus, was immobilized on cotton (CO) in a layer-by-layer (LbL) approach with polyvinylamine (PVAm) as the oppositely charged electrolyte to create a partly bio-based flame-retardant finish. PVAm was employed as a synthetic nitrogen source with the highest density of amine groups of all polymers. Vertical flame tests revealed a flame-retardant behavior with no afterflame and afterglow time for a coating of 15 bilayers (BL) containing 2% phosphorus and 1.4% nitrogen. The coating achieved a molar P:N ratio of 3:5. Microscale combustion calorimetry (MCC) analyses affirmed the flame test findings by a decrease in peak heat release rate (pkHRR) by more than 60% relative to unfinished CO. Thermogravimetric analyses (TGA) and MCC measurements exhibited a shifted CO peak to lower temperatures indicating proceeding reactions to form an isolating char on the surface. Fourier transform infrared spectroscopy (FTIR) coupled online with a TGA system, allowed the identification of a decreased amount of acrolein, methanol, carbon monoxide and formaldehyde during sample pyrolysis and a higher amount of released water. Thereby the toxicity of released volatiles was reduced. Our results prove that PA enables a different reaction by catalyzing cellulosic dehydration, which results in the formation of a protective char on the surface of the burned fabric.

Facile Preparation of Flame Retardant Cotton Fabric via Adhesion of Mg(OH)2 by the Assistance of Ionic Liquid

A new approach for flame retardant functional finishing of textiles was explored to improve flame retardancy of cotton fabrics by simple physical adhesion method. Mg(OH)2 was adhered to cotton fiber with the aid of fiber swelling in ionic liquid on heating and shrinkage on washing to obtain flame retardancy. The effects of immobilizing condition and methods on flame retardancy were discussed. The surface morphology, crystal structure, combustion behavior, thermal and physical properties of cotton fabric adhered with Mg(OH)2 were analyzed. The afterflame time and afterglow time of adhered cotton fabric were significantly reduced to less than 5 s. The thermal weight loss of cotton fabric was increased by 11.7% and the total heat released per unit mass was decreased by 20.9% after MH adhesion. The simple eco-friendly adhesion method provided a convenient approach for the development and application of flame retardant functional cellulosic textiles.

PRODUCTION OF FUEL BRIQUETTES FROM SHEA NUT SHELLS AND MILLET STALK

In an effort to provide an affordable firewood alternative source of fuel to the rural households in Nigeria, this study was carried out to produce some biomass briquettes (Shea nut shells and millet stalk) prepared using a briquetting machine (Extruding machine). The proximate analysis of the raw samples and briquettes biomass were determined. Different samples of briquettes were produced by blending varying ratios of Shea nut shells and millet stalk of 100:0, 80:20, 70:30, 60:40, 50:50, using starch as adhesive. The results of the briquettes tested was found to have moisture content for Shea nut shell and Millet stalk 2.5% and 3.0%, ash content 2.5% and 4.5% and volatile of 16.0% and 11.0%. A test on physical parameters like ignition time, combustibility test and afterglow time were determined and it was observed that ignition time increases with high volatile matter and with high percentage of ash and moisture content it ignites slowly. Water boiling test was also performed to compare between butane gas and fuel briquettes, it was observed that both butane gas and briquettes took the same time to boil 2litre of water (18 minutes).

Effect of RE3+ Codopant on Afterglow Time of SrS:Eu2+,RE3+

The longest afterglow time of an orange-red- emitting SrS:Eu2+,Pr3+ afterglow phosphor by visible light irradiation was about 1010 minutes was previously achieved by varying the synthetic conditions such as amount of Li+ added, reduction temperature, reduction time, and initial Eu/Sr and Pr/Sr atomic ratios in previous paper. Therefore, this study reports on the effect of the RE3+ codopants on the afterglow time of an orange-red-emitting SrS phosphor by visible light irradiation. SrSO4:Eu3+,RE3+(RE3+ = Tm3+, Er3+, Tb3+, Nd3+, Pr3+, Ce3+, and La3+), which was the precursor for SrS phosphors, was synthesized via a liquid-phase reaction. SrSO4:Eu3+,RE3+ was pressurized at 10 MPa for a few minutes to form a compact, which was then heated under a H2S or Ar-H2 (5 mol%) reductive atmosphere at 1400 °C for 2.5 h to generate the SrS:Eu3+,RE3+ afterglow phosphor. The emission color of the SrS:Eu2+,RE3+ afterglow phosphor was orange-red and its emission peak was observed around 610 nm. The excited band of the phosphor was in the range of visible light more than 440 nm. The emission and excitation spectra of the SrS:Eu2+,RE3+ afterglow phosphor were not dependent on the RE3+ codopants. However, the afterglow time of SrS:Eu2+,RE3+ phosphor was increased with the increase of ionic radius of the coactivator. The longest afterglow time of SrS:Eu2+,Ce3+ phosphor by irradiating for 5 minutes at 1000 lx which was created from a D65 lamp was 1376 minutes. This was 9.5 times longer than that of a commercial available phosphor (CaS:Eu2+,Tm3+).

Dy3+ Doping Blue-Green Sr4Al14O25:Eu2+ Phosphor for Enhancing Luminescent Properties and the Mechanism Study

Dy3+ doped blue-green Eu2+ doped strontium aluminate (Sr4Al14O25:Eu2+) phosphor was prepared using a high temperature solid state method and the influence of the doped Dy3+ on the luminescent properties was studied using X-ray diffraction, scanning electron microscopy, fluorescence spectroscopy and a series of other characterization methods. It is found that Dy3+ doping can enhance the luminescent intensity and extend the afterglow time. The luminescent mechanism of rare earth ions doped strontium aluminate phosphor was also discussed deeply, the effects of the doping amount on the luminescent properties has been made detailed explanation and description. This work has important theoretical significance for the development of higher brightness and longer afterglow blue-green phosphors.