高分子材料加工技术专业英语 Flame Retardants fire initiation and combustion process讲稿.docVIP

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高分子材料加工技术专业英语 Flame Retardants fire initiation and combustion process讲稿.doc

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PAGE 1 PAGE 1 Fire initiation and combustion process教学设计教学内容与设计时间分配或备注说明 How does polymer get to burn? Let’s watch a short video. 一、Process of combustion 1. heating of the fuel source. 2. decomposition of the fuel source into combustible and non-combustible materials. 3. ignition of the combustible fuel and air mixture to produce a flame. The fire triangle demonstrates that combustion need at least three factors : that is fuel,heat,and air (oxygen). The three factors mentioned above are related to each other in the combustion process: the combustion of plastics will be taken as an example in the following. The combustion of plastics is a process comprising many steps and basically initiated by a heat source initiating the decomposition of the polymer. These two steps, heating and decomposition of the polymer consume energy (endothermic process) for overcoming the high binding energies between individual atoms (200 to 400 kJ/mole). Combustible gases are formed, which mix the oxygen of the air and ignite. This leads to the exothermic part of the process, i. e. flame propagation and heat release. Pyrolysis of the polymer is reinforced by thermal feedback (heat release), which fuels the flame at an increasing level. The flame is supported by extremely high energy H· and OH· radicals, which confer a high velocity to the flame. Flame retardants may inhibit the chemical reactions in the flame by removing the high energy radicals, or initiate the formation of a charred layer on the surface. Thus, the polymer is protected against the attack of heat and oxygen of the air and prevents the formation of flammable gas mixtures. Flame retardants Vs non-flame retardants 二、练习Exercises 1. The fire combustion need at least three factors :that is fuel,heat,and air（oxygen） . 2.Plastics are intrinsic combustible,so it can burn directly,need not form combustible molecules. 3.Pyrolysis of the polymer is a heat release reaction. 4.Combustible gases need to mix the oxygen of the