Anisotropy of expandable graphite to explain its behavior as a flame-retardant

2020 ◽  
pp. 073490412096963
Author(s):  
Tsilla Bensabath ◽  
Johan Sarazin ◽  
Serge Bourbigot
Keyword(s):  
Flame Retardant ◽  
Heat Dissipation ◽  
Experimental Approach ◽  
Hot Spot ◽  
Mechanisms Of Action ◽  
Expandable Graphite ◽  
Thermal Barrier ◽  
Barrier Effect ◽  
Cone Calorimetry ◽  
Out Of Plane

Expandable graphite is used as a flame-retardant in polymers. Its expansion on heating leads to a network of graphite worms which acts as a thermal barrier. However, mechanisms of action of worms are not yet well known. An original experimental approach is performed to study the heat dissipation in the network of worms. The network is made by the burning of polypropylene with 10 wt% expandable graphite during cone calorimeter experiment. After the burning, a hot spot is applied on the char. Temperature is monitored at different locations of sample during the combustion and after the application of the hot spot. During cone calorimetry, the char develops homogeneously over the whole sample. The hot spot test evidences the anisotropy of the entangled network of graphite worms. This anisotropy of heat conductivity allows the dissipation of heat in-plane and poorly out of plane, which explains the thermal barrier effect made by entangled worms.

scholarly journals Mechanically Sustainable Starch-Based Flame-Retardant Coatings on Polyurethane Foams

Polymers ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1286
Author(s):  
Kyung-Who Choi ◽  
Jun-Woo Kim ◽  
Tae-Soon Kwon ◽  
Seok-Won Kang ◽  
Jung-Il Song ◽  
...  
Keyword(s):  
Heat Release ◽  
Flame Retardant ◽  
Coating Layer ◽  
Real Life ◽  
Polyurethane Foams ◽  
Layer By Layer ◽  
Toxic Substances ◽  
Cone Calorimetry ◽  
Coating Agent ◽  
Cone Calorimeter Test

The use of halogen-based materials has been regulated since toxic substances are released during combustion. In this study, polyurethane foam was coated with cationic starch (CS) and montmorillonite (MMT) nano-clay using a spray-assisted layer-by-layer (LbL) assembly to develop an eco-friendly, high-performance flame-retardant coating agent. The thickness of the CS/MMT coating layer was confirmed to have increased uniformly as the layers were stacked. Likewise, a cone calorimetry test confirmed that the heat release rate and total heat release of the coated foam decreased by about 1/2, and a flame test showed improved fire retardancy based on the analysis of combustion speed, flame size, and residues of the LbL-coated foam. More importantly, an additional cone calorimeter test was performed after conducting more than 1000 compressions to assess the durability of the flame-retardant coating layer when applied in real life, confirming the durability of the LbL coating by the lasting flame retardancy.

scholarly journals Hotspot Temperature Prediction of Dry-Type Transformers Based on Particle Filter Optimization with Support Vector Regression

Symmetry ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1320
Author(s):  
Yuanyuan Sun ◽  
Gongde Xu ◽  
Na Li ◽  
Kejun Li ◽  
Yongliang Liang ◽  
...  
Keyword(s):  
Particle Filter ◽  
Support Vector Regression ◽  
Heat Dissipation ◽  
Hot Spot ◽  
Load Capacity ◽  
Regression Method ◽  
Support Vector ◽  
Temperature Prediction ◽  
Support Vector Regression Model ◽  
Load Rate

Both poor cooling methods and complex heat dissipation lead to prominent asymmetry in transformer temperature distribution. Both the operating life and load capacity of a power transformer are closely related to the winding hotspot temperature. Realizing accurate prediction of the hotspot temperature of transformer windings is the key to effectively preventing thermal faults in transformers, thus ensuring the reliable operation of transformers and accurately predicting transformer operating lifetimes. In this paper, a hot spot temperature prediction method is proposed based on the transformer operating parameters through the particle filter optimization support vector regression model. Based on the monitored transformer temperature, load rate, transformer cooling type, and ambient temperature, the hotspot temperature of a dry-type transformer can be predicted by a support vector regression method. The hyperparameters of the support vector regression are dynamically optimized here according to the particle filter to improve the optimization accuracy. The validity and accuracy of the proposed method are verified by comparing the proposed method with a traditional support vector regression method based on the real operating data of a 35 kV dry-type transformer.

scholarly journals Synergistic Flame-Retardant Mechanism of Dicyclohexenyl Aluminum Hypophosphite and Nano-Silica

Polymers ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 1211 ◽  
Author(s):  
Heng Zhang ◽  
Junliang Lu ◽  
Hongyan Yang ◽  
Heng Yang ◽  
Jinyan Lang ◽  
...  
Keyword(s):  
Flame Retardant ◽  
Combustion Surface ◽  
Carbon Layer ◽  
Material Surface ◽  
Infrared Analysis ◽  
Index Test ◽  
Nano Silica ◽  
Cone Calorimetry ◽  
Flame Retardant Property ◽  
Aluminum Hypophosphite

The flame retardant dicyclohexenyl aluminum hypophosphite (ADCP) and nano-silica are added to PA66 to improve flame retardant property of the composite. The flame-retardant property of the composite is tested via oxygen index test, vertical burning test, and cone calorimetry test. Combustion residues are tested using scanning electron microscopy, EDS spectroscopy, and Fourier infrared analysis. Results show that flame-retardant ADCP can effectively promote the formation of a porous carbon layer on the combustion surface of PA66. Nano-silica easily migrates to the material surface to improve the oxidation resistance of the carbon layer and the density of the carbon layer’s structure. It can also effectively prevent heat, flammable gases, and oxygen from entering the flame zone and enhance the flame retardant properties of ADCP.

scholarly journals Development of Inherently Flame—Retardant Phosphorylated PLA by Combination of Ring-Opening Polymerization and Reactive Extrusion

Materials ◽  
2019 ◽  
Vol 13 (1) ◽  
pp. 13 ◽  
Author(s):  
Rosica Mincheva ◽  
Hazar Guemiza ◽  
Chaimaa Hidan ◽  
Sébastien Moins ◽  
Olivier Coulembier ◽  
...  
Keyword(s):  
Heat Release ◽  
Flame Retardant ◽  
Ring Opening ◽  
Coupling Reaction ◽  
Reactive Extrusion ◽  
Ring Opening Polymerization ◽  
Hexamethylene Diisocyanate ◽  
Cone Calorimetry ◽  
Loss Cone ◽  
Ul 94

In this study, a highly efficient flame-retardant bioplastic poly(lactide) was developed by covalently incorporating flame-retardant DOPO, that is, 9,10-dihydro-oxa-10-phosphaphenanthrene-10-oxide. To that end, a three-step strategy that combines the catalyzed ring-opening polymerization (ROP) of L,L-lactide (L,L-LA) in bulk from a pre-synthesized DOPO-diamine initiator, followed by bulk chain-coupling reaction by reactive extrusion of the so-obtained phosphorylated polylactide (PLA) oligomers (DOPO-PLA) with hexamethylene diisocyanate (HDI), is described. The flame retardancy of the phosphorylated PLA (DOPO-PLA-PU) was investigated by mass loss cone calorimetry and UL-94 tests. As compared with a commercially available PLA matrix, phosphorylated PLA shows superior flame-retardant properties, that is, (i) significant reduction of both the peak of heat release rate (pHRR) and total heat release (THR) by 35% and 36%, respectively, and (ii) V0 classification at UL-94 test. Comparisons between simple physical DOPO-diamine/PLA blends and a DOPO-PLA-PU material were also performed. The results evidenced the superior flame-retardant behavior of phosphorylated PLA obtained by a reactive pathway.

Preparation of expandable graphite using a hydrothermal method and flame-retardant properties of its halogen-free flame-retardant HDPE composites

2010 ◽  
Vol 18 (4) ◽  
pp. 483-488 ◽  
Author(s):  
Kuang-Chung Tsai ◽  
Hsu-Chiang Kuan ◽  
Huang-Wen Chou ◽  
Chen-Feng Kuan ◽  
Chia-Hsun Chen ◽  
...  
Keyword(s):  
Flame Retardant ◽  
Hydrothermal Method ◽  
Expandable Graphite ◽  
Flame Retardant Properties ◽  
Halogen Free

A facile strategy to fabricate microencapsulated expandable graphite as a flame-retardant for rigid polyurethane foams

2015 ◽  
Vol 132 (31) ◽  
pp. n/a-n/a ◽  
Author(s):  
Xiao-Liang Zhang ◽  
Hong-Ji Duan ◽  
Ding-Xiang Yan ◽  
Li-Quan Kang ◽  
Wei-Qin Zhang ◽  
...  
Keyword(s):  
Flame Retardant ◽  
Polyurethane Foams ◽  
Expandable Graphite ◽  
Rigid Polyurethane Foams
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