Halogenated epoxides were used to reduce the flammability of epoxy resins

Epoxy resin has very low thermal stability, light stability and high flammability.When the temperature exceeds 150℃, it is decomposed and ignited at 400 ℃.The linear and weight velocities of the combustion are 3.4 -- 4 mm/min and 7 -- 8 g/cm 2, respectively.The corresponding surface temperature at combustion -- 500-530 ° c, flame temperature -- 950-970 ° c.

The combustibility of epoxy polymers, like other polymers, is related to their chemical composition.In particular, the flame retardancy of these polymers is mainly affected by the ratio of oxygen to carbon in the oligomer molecules (oxygen index = 0.198-0.238).Generally speaking, combustion increases with the increase of oxygen content in the molecule.Because of the large ratio of O to C, aliphatic epoxies burn faster.The flammability of epoxy polymers is affected by the presence of curing agents.Epoxy oligomers cured with dicarboxylic anhydride are more combustible than similar oligomers cured with amines.

In the preparation of epoxy resin-based mixtures containing curing agents, fillers, and other components, the flame retardant properties of the curing materials can be obtained by the following means:Flame retardant curing agent;Special flame retardant additives;Flame retardant filler.

The substituents that give flame retardancy to epoxy oligomers are additives containing halogen, phosphorus, nitrogen and sulfur atoms.Additive - inorganic or organic matter that can be used alone or in combination.As the flame retardant additives of halogen, chlorine and bromine are mainly used.The dissociation energy of carbon-chlorine bond is 280.7 kilojoule/gram molecule, while that of carbon-bromo bond is 226.5 kilojoule/gram molecule.Therefore, the brominated mixture is easy to form groups when separated, which increases the efficiency of flame retarding.The efficiency of halogenated flame retardant additives is listed as follows: halogenated aliphatic compounds, halogenated lipolycyclic compounds, and halogenated aromatic compounds.The main problem is that when these flame-retardant additives are added to the polymer, their thermal stability order is just the opposite.In this way, the category and method of selection of epoxy polymer-based materials with high flame retardancy take into account the scope of application, conditions of material processing, price, properties and other factors.As a result of the use of various mixtures of flame retardants, their properties have been successfully improved.A common material with good properties, characteristics, and high flame retardancy. In some cases, a large number of halogenated compounds are introduced to give polymers flame retardancy.

The method of giving flame retardancy to epoxy polymers is widely used to introduce halogenated compounds.As additives used in polymeric materials, and has been produced on an industrial scale, according to the information has been about 2300 kinds of chemical compounds and mixtures.Note that in almost all flame retardants using halogenated organically-derived compounds, the amount of antimony trioxide is required to match it.In the absence of chlorinated derivatives, antimony trioxide does not affect the flame retardant properties of the polymer.The flame retarding effect of antimony oxide in polymer combustion depends on the flame retarding mechanism of the flame retarding agent.

The flame propagates in the gas phase due to the free H and OH groups formed as branched chains.You take the H, you take the OH, you take the water, you take the R, you oxidize it, you take the OH again, and you keep burning.As the H and OH groups decrease, the combustion slows down and the flame goes out.In the presence of chlorocarbons, antimony trioxide performs chemical reactions such as (1) in the preheated decomposition range.The antimony oxide layer on the surface of the material at a temperature above 600℃ is reacted in the flame zone as shown in the (2) example.From equation (2), it can be seen that 2O3 reacts with all HCl to form OCl, and further reacts in the gas phase to precipitate antimony trioxide, resulting in double decomposition.Thus, antimony trioxide ACTS as a reaction with hydrogen chloride and prevents its premature evaporation, thus reducing the gradient of hydrogen halide decomposition.The premature evaporation of hydrogen chloride can lead to the loss of halogen in the polymer and accelerated combustion, as it can even burn violently at low halogen levels.Antimony trioxide ACTS with it to keep it in the polymer.To this end, determine the appropriate proportion of component content in the polymer, some content beyond the appropriate range, will increase the combustion of the polymer.

In this way, the flame retardants are introduced into the polymer to produce a combustion suppression, reducing the heat in the combustion zone.In addition, antimony halide compounds form a protective film on the polymer surface, preventing oxygen from entering the combustion zone and extinguishing the flame as a result.