Mechanisms for Flame Retardancy and Smoke suppression -A Review

The prevailing mechanisms for halogen and phosphorus flame retardancy are reviewed. Halogens act in the vapor phase and phosphorus can act in either the vapor or condensed phase depending on the specific phos phorus compound and the chemical composition of the polymer. Halogen- antimony synergy is discussed. Convincing evidence is presented for bromine- phosphorus synergy in specific polymers. The mode of decomposition of polycarbonate is shown and the effect of salts of organic acids in changing the mode of decomposition hence producing a more flame resistant polymer is shown. Intumescence in polyolefins is discussed. Inorganic metal hydrates used in large concentration cool by endothermically releasing a large concentration of water. The effect of boron compounds is discussed. Methods of smoke suppres sion are presented as is the role of zinc borate, molybdenum and tin compounds acting as Lewis acids in PVC.

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Theoretical Insight into the Reversal of Chemoselectivity in Diels-Alder Reactions of α,β-Unsaturated Aldehydes and Ketones Catalyzed by Brønsted and Lewis Acids

Organics ◽

10.3390/org2010004 ◽

2021 ◽

Vol 2 (1) ◽

pp. 38-49

Author(s):

Lakhdar Benhamed ◽

Sidi Mohamed Mekelleche ◽

Wafaa Benchouk

Keyword(s):

Lewis Acids ◽

Major Product ◽

Diels Alder ◽

Unsaturated Ketone ◽

Unsaturated Aldehydes ◽

Aldehydes And Ketones ◽

Theoretical Insight ◽

Insight Into ◽

Good Agreement

Experimentally, a reversal of chemoselectivity has been observed in catalyzed Diels–Alder reactions of α,β-unsaturated aldehydes (e.g., (2E)-but-2-enal) and ketones (e.g., 2-hexen-4-one) with cyclopentadiene. Indeed, using the triflimidic Brønsted acid Tf2NH as catalyst, the reaction gave a Diels–Alder adduct derived from α,β-unsaturated ketone as a major product. On the other hand, the use of tris(pentafluorophenyl)borane B(C6F5)3 bulky Lewis acid as catalyst gave mainly the cycloadduct of α,β-unsaturated aldehyde as a major product. Our aim in the present work is to put in evidence the role of the catalyst in the reversal of the chemoselectivity of the catalyzed Diels–Alder reactions of (2E)-but-2-enal and 2-Hexen-4-one with cyclopentadiene. The calculations were performed at the ωB97XD/6-311G(d,p) level of theory and the solvent effects of dichloromethane were taken into account using the PCM solvation model. The obtained results are in good agreement with experimental outcomes.

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Correction to: The role of plants in the formation of the topsoil chemical composition in different climatic conditions of steppe landscape

Plant and Soil ◽

10.1007/s11104-021-05051-3 ◽

2021 ◽

Author(s):

Irina Yu. Kudrevatykh ◽

Pavel I. Kalinin ◽

Gennady V. Mitenko ◽

Andrey O. Alekseev

Keyword(s):

Chemical Composition ◽

Climatic Conditions

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A triple combination of treatments on moderate COVID-19

Open Medicine ◽

10.1515/med-2021-0279 ◽

2021 ◽

Vol 16 (1) ◽

pp. 769-772

Author(s):

ChunMiao Bao ◽

BinBin Li ◽

YuFeng Zhou

Keyword(s):

Medical Records ◽

Clinical Characteristics ◽

Smoking Status ◽

Length Of Hospital Stay ◽

Convincing Evidence ◽

Triple Combination ◽

Viral Shedding ◽

Null Effect ◽

Treatment Start

Abstract Objective A triple combination of interferon (IFN) α-2b, lopinavir tablets, and umifenovir was used to treat COVID-19 patients. It is important to explore whether the benefit of this therapy is time dependent. Methods A cohort of moderate COVID-19 patients (n = 54) was admitted for hospitalization. The demographic (age, gender, and smoking status) and clinical characteristics (epidemiological trace and comorbidity) were collected from the digital medical records. The length of hospital stay (LOS) and the viral shedding time (VST) were set as the outcomes for COVID-19 cases. Results After control for age, sex, epidemiological trace, smoking, and comorbidity, the time of treatment start had null effect on VST (IRR = 1.09; 95% CI = 0.91–1.30; p = 0.33) or LOS (IRR = 1.10; 95% CI = 0.94–1.28; p = 0.23). Conclusion There is no convincing evidence to support a pivotal role of the timing of the therapy in the prognosis of moderate COVID-19 cases.

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Elucidating the Origin of the Toxicity of Nano-CeO2 to Chlorella pyrenoidosa：the Role of Specific Surface Area and Chemical Composition

Environmental Science Nano ◽

10.1039/d0en01177k ◽

2021 ◽

Author(s):

Changjian Xie ◽

Yuhui Ma ◽

Peng Zhang ◽

Junzhe Zhang ◽

Xiaowei Li ◽

...

Keyword(s):

Chemical Composition ◽

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Aquatic Environment ◽

Cerium Dioxide ◽

Environmental Application ◽

Ecotoxicological Effects

With the increasing environmental application and discharge of nano cerium dioxide (nano-CeO2), it is urgent to fully understand its ecotoxicological effects on the aquatic environment. This study for the first...

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Effect of Triaryl Phosphate, Zinc and Zinc Borate on Fire Properties of High Impact Polystyrene and High Impact Polystyrene-Polyphenylene Oxide Blend (Modified-Polyphenylene Oxide

Journal of Fire Sciences ◽

10.1177/073490419401200605 ◽

1994 ◽

Vol 12 (6) ◽

pp. 529-550 ◽

Cited By ~ 5

Author(s):

Ramazan Benrashid ◽

Gordon L. Nelson ◽

Donald J. Ferm

Keyword(s):

Flame Retardancy ◽

High Impact ◽

Zinc Borate ◽

Polyphenylene Oxide ◽

High Impact Polystyrene ◽

Smoke Generation ◽

Flame Retarded ◽

Rate Of Heat Release ◽

Fire Properties ◽

Phase Activity

Samples of m-PPO (virgin and flame retarded) and high impact polystyrene blended with zinc and zinc borate (2ZnO·3B2O3·3.5H 2O), were pre pared. The effect of triaryl phosphate on the flame retardancy of PPO-HIPS in conjunction with zinc and zinc borate was studied. For polystyrene zinc borate shows some reduction in smoke generation. Zinc, however does not show any effect on smoke generation for high impact polystyrene. Triphenyl phosphate shows minimal flame retardancy in HIPS which is not enhanced by zinc. Addition of zinc gives an increase in oxygen index for FR m-PPO, whereas zinc borate decreases the OI values. Zinc borate may sequester triaryl phos phate and thus eliminate its vapor phase activity. Zinc borate shows a signifi cant reduction in smoke generation and rate of heat release for m-PPO.

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Research on Ethanol Production by Biological Fermentation of Potato Pulp

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.805-806.281 ◽

2013 ◽

Vol 805-806 ◽

pp. 281-285

Author(s):

Zhong Xu

Keyword(s):

Chemical Composition ◽

Ethanol Production ◽

Production Rate ◽

Liquid Ratio ◽

Fermentation Time ◽

Potato Pulp ◽

Fermentation Temperature ◽

Ethanol Production Rate ◽

Solid Liquid

Bioconversion of potato pulp to fuel ethanol, analysing the potato pulp chemical composition and determining the potato pulp in the role of microorganism produce ethanol under the best conditions is the major research. An analysis of the chemical composition of potato pulp showed that : the basic ingredients are Protein (9.72%), Starch (25.52%), Cellulose (17.90%). The effects of ethanol production rate of solid-liquid ratio, fermentation temperature, inoculumconcertration, fermentation time. The results showed that: the best conditions producting ethanol from potato pulp obtained by single factor experiments are: solid-liquid ratio: 1:15, fermentation temperature: 35°C, inoculumconcertration: 3mL, fermentation time: 20h. Under this occasion, the ethanol production rate was 0.183mL·g-1.

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