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Fire Hazards and Associated Terminology
Published in Asim Kumar Roy Choudhury, Flame Retardants for Textile Materials, 2020
The thermal processes and combustion products of organic products occur in a progressive and definable cycle as shown in Figure 1.1. When heat is applied, the temperature of the fiber increases until the pyrolysis temperature (Tp) is reached. At this temperature the fiber undergoes irreversible chemical changes, producing nonflammable gases (carbon dioxide, water vapor, and higher oxides of nitrogen and sulfur), flammable gases (carbon monoxide, hydrogen and many oxidizable organic molecules), tars (liquid condensates) and carbonaceous char. As the temperature continues to rise, the tars also pyrolyze, producing more flammable and nonflammable gases and char. When combustion temperature (TC) is reached, the flammable gases combine with oxygen in the process called combustion, which is a series of gas-phase free radical reactions. These highly exothermic reactions generate large amounts of heat and light. The generated heat provides additional thermal heat for the pyrolysis process to continue. More and more flammable gases and consequently, higher and higher amounts of heat are generated causing devastating effects. In the case of burning of textiles, the speed or rate of heat release is more important than the amount of generated heat (Schindler and Hauser, 2004). An important factor in combustion is the Limiting Oxygen Index (LOI), which is the percentage of oxygen in the fuel mix needed to support combustion. The higher this number is, the more difficult the combustion is.
Thermoplastics Foams
Published in Omar Faruk , Jimi Tjong , Mohini Sain, Lightweight and Sustainable Materials for Automotive Applications, 2017
Sai Aditya Pradeep, Srishti Shukla, Nathaniel Brown, Srikanth Pilla
Limiting oxygen index (LOI) can be defined as the minimum concentration of oxygen required to support the combustion of a polymer. To evaluate LOI, a long prismatic sample, supported in a vertical glass column, is ignited at the top and allowed to burn downward. A mixture of air stream, containing O2 and N2, is then passed through the column with a gradual reduction in percentage of O2 in the air stream. The minimum concentration required to just support combustion is recorded and quoted as a percentage. Although LOI is used as a measure of flammability of a material, it cannot explain the behavior of the same material when burnt in open atmosphere. LOI values for various thermoplastic resins have been mentioned in Table 11.1.
Preparation And Characterization of Polybenzoxazine/Plasticized PVC-Based Fumed Silica Composites
Published in Sajith Thottathil, Sabu Thomas, Nandakumar Kalarikkal, Didier Rouxel, Advanced Polymeric Materials for Sustainability and Innovations, 2018
Hussein Ali, S. Radhakrishnan, M. B. Kulkarni
The limiting oxygen index (LOI) is the minimum concentration of oxygen, expressed as a percentage that will support combustion of a polymer. LOI values were determined by standardized tests (ASTM D2863) (Table 4.3). The LOI of 77.6PVC/19.4PBZ/3FS provided a value as high as 27, which is much greater than that of the PPVC, 23 %. Therefore, these composites can be considered as good prospects with flame retardancy which can be useful in several applications such as electronic industries, automotive, as well as in aerospace industries.
Synthesis of a reactive lignin-based flame retardant and its application in phenolic foam
Published in Environmental Technology, 2023
Minghao Zhou, Lei Zhong, Lihong Hu, Yonghong Zhou, Xiaohui Yang
Limiting oxygen index (LOI) is an important parameter to measure the flame retardant performance of materials. The LOI refers to the minimum oxygen concentration of materials in the mixture of N2 and O2 flame under specified conditions, which is expressed by the percentage of the volume of oxygen. The higher the LOI, the less combustible the material. As can be seen from Figure 5(c), LOI of PF was 29.6%. However, LOI was improved significantly after NP-L was added into PF, and LOI remained above 55% when the replacement amount of modified lignin was 5–15% because the carbon layer generated by the unreacted lignin wrapped the inner core and then affected the combustion after the addition of modified lignin. In addition, due to the presence of melamine, foam will release non-combustible gas during combustion, thus inhibiting combustion. The presence of P also formed phosphate, which promotes the formation of carbon layer to inhibit combustion [36]. Diluting the oxygen content and generating phosphate to promote the formation of carbon layers to inhibit combustion. When the replacement amounts were 25% and 30%, the LOI dropped to 54.5% and 53.2%, respectively. It might be caused by the uneven mixing caused by the high viscosity of phenolic resin. Additionally, due to the low reactivity of modified lignin, the insufficient reaction with formaldehyde with the increase of its substitution amount may also cause the slight decrease of LOI. The results showed that the introduction of lignin-based retardant containing nitrogen and phosphorus improved the flame retardancy of phenolic foam significantly.
Synthesis and characterisation of rice-straw-based grafted polymer composite by free radical copolymerisation
Published in Indian Chemical Engineer, 2019
Aparna Mukherjee, Deepshikha Datta, Gopinath Halder
The percentage of oxygen that has to be present to support combustion of composites is known as the limiting oxygen index (LOI). The flammability decreases with increase in LOI. The minimum oxygen concentration in the oxygen/nitrogen mixture required to maintain flame combustion of 3 min or that burns 5 cm of the sample kept vertically upward gives the determination of LOI. LOI can be expressed by [22]
Mechanical property of lignin-modified phenolic foam enhanced by whisker silicon
Published in Journal of Dispersion Science and Technology, 2020
Na Zhang, Lihong Hu, Yajun Guo, Caiying Bo, Puyou Jia, Baofang Zhang, Yonghong Zhou
Limiting oxygen index (LOI) is an important parameter to measure the flame retardant properties of insulation materials. It is defined as the minimum oxygen concentration required for the combustion of a sample in an oxygen and nitrogen mixture at 23 °C ± 2 °C.