Dongguan Changyong Win Insulation Material Co., Ltd. is a private high-tech enterprise specializing in the production of Teflon board. Let's analyze the basic knowledge of plastics by our Teflon board manufacturers: the basic principles of flame retardant modification! Interested friends can watch it together!

Combustion process of 1. plastics

To understand the principle of plastic flame retardant, we must first understand the combustion process of plastic; the combustion process of plastic is an extremely complex thermal oxidation reaction, resulting in the basic elements of combustion for heat, oxygen and combustible gas.

It is generally believed that the combustion of plastics has gone through the following 3 stages:

The first stage, the thermal initiation process. Heat from an external heat source or fire source causes the plastic to undergo a phase change (I. e., transition from solid to liquid) and a chemical change.

The second stage, thermal degradation process. This 1 process is an endothermic reaction. When the heat absorbed by the plastic is sufficient to overcome some weak bond energy between atoms in the molecule, the plastic begins to degrade. The essence of this reaction is a 1 free radical chain reaction in the presence of oxygen in the air, and the result of the reaction produces gas-phase combustibles such as various monomers flammable hydrocarbons.

The third stage, the ignition process. When the concentration of combustibles generated by the second stage thermal degradation reaction reaches the ignition limit, it meets with oxygen in the atmosphere.

2. flame retardant mechanism

The addition of flame retardants in a certain proportion of plastics can increase the oxygen index and the flame retardant effect is obvious. Of course, the oxygen index only indicates the flammability of the material and the flame retardancy of the flame retardant, and a series of parameters should also be used, such as the critical parameter of thermal spontaneous combustion, thermal ignition energy, thermal spontaneous combustion temperature, etc. In general, when plastics containing flame retardants are burned, the flame retardants act in many ways in different reaction zones (gas phase, * condensed phase). The effect of the flame retardant may also be different for different materials.

The mechanism of action of flame retardants is more complex. However, the aim is always to cut off the combustion cycle by physical and chemical means. The effect of flame retardants on the combustion reaction is manifested in the following aspects:

(1) The flame retardant located in the condensed phase is endothermic and decomposed, so that the relative temperature in the condensed phase is slowed down to delay the thermal decomposition temperature of the plastic, and the heat of vaporization of the non-combustible gas generated during the thermal decomposition of the flame retardant is used to reduce the temperature.

(2) The flame retardant is decomposed by heat, and the flame retardant capturing the OH (hydroxyl) free radical in the combustion reaction is released, so that the combustion process according to the free radical chain reaction terminates the chain reaction.

(3) Under the action of heat, the flame retardant appears endothermic phase transition, which prevents the temperature rise in the condensed phase and slows down the combustion reaction until it stops.

(4) Catalytic thermal decomposition of the condensed phase to produce solid phase products (coking layer) or foam layer, which hinders heat transfer. This keeps the temperature of the condensed phase at a relatively low level, resulting in a reduced rate of formation of the starting material (combustible gas decomposition products) as a gas phase reaction.