We are familiar with such words as halogen - free and halogen - free flame retardants, so what is the concept of halogen free? Why do we have no halogen?
What is the concept of halogen free?
Halogen (halogen) of Article VII of A family in the periodic table of elements, non metallic elements, including fluorine, chlorine (Fluorine) (Chlorine) (Bromine), bromine and iodine (Iodine), astatine (Astatine) of five kinds of elements, element symbols are F (f), Cl (CL), Br (BR), I (iodine), At (astatium), for astatine radioactive elements, therefore, often say that the halogen refers to the four elements of fluorine, chlorine, bromine, iodine, especially in the product polymer material usually exists in the form of organic compound.
The source of the concept of non halogen: Eu (European Union) in the European Union in electrical and electronic materials (Restriction of the harm disable Use of Hazardous Substances in electrical and electronic equipment, referred to as RoHS) decided to ban PBB in July 1, 2006 (Polybrominated Biphenyls) instructions and PBDE (Polybrominated Diphenyl Ethers) and the use of brominated flame retardants.
Halogen free Halogen Free or Non-Halogen, according to regulations IEC 61249-2-21 requirements: bromine and chlorine content is less than 900ppm, and the sum of bromine and chlorine content is less than 1500ppm, it is halogen free.
Halogens are often used as flame retardants and are used in electronic components and materials, product shells, plastic and so on. This kind of flame retardant can not be recycled, and it will release harmful substances during combustion and heating, and threaten the health of human body, environment and the next generation. Therefore, in the limit of halogen content, all countries are using the corresponding methods to make efforts, this is halogenation.
Why no halogenation?
1. The toxicity inherent in the halogen organic matter itself is a threat to the environment and human health.
2, adding halogen in polymers such as plastics is mainly used to increase ignition point. It has higher ignition point than common polymer materials, and is about 300 degrees centigrade. When burning, it will give off halogenated gas, absorb oxygen quickly, and extinguish the fire. However, according to statistics, 80% of the deaths in the fire are caused by suffocation, which leads to asphyxiation is harmful substances in the smoke, while halogen containing flame retardants are the main source of plastic products. Halogen containing flame retardants, such as dioxins and benzofurans (Benzfuran), will be released when they are burned or burned. They will cause heavy smoke, odour and high toxic gases, and cause cancer. They can not be discharged after ingestion, which is not environmentally friendly and affects human health.
3. The organic wastes containing halogen organic wastes will cause two pollution and produce highly toxic organic compounds such as dioxin.
4, plastic in the process of injection molding, halogen will release hydrogen halide, corrosion mold.
5, halogen containing flame retardant materials will produce large amounts of toxic gases in the combustion (such as dioxins, furans, DIOXIN) damage to the environment, and can exist in the environment for years, even life accumulated in organisms, can not be discharged, therefore, many international companies are actively promoting the complete abolition of halogen containing materials.
Note: dioxin is also transliterated to DELL, which is the general name of four chloro two benzo - -P- dioxin (PCDDs) and polychlorinated two benzofuran (PCDFs). Because of its toxicity is 900 times 130 times of sodium cyanide, arsenic, known as the "poison of poison".
The flame retardancy mechanism of the flame retardant has been introduced before. Halogen free flame retardants are often encountered, this is mainly introduced here. Phosphorus nitrogen expansion type flame retardant is representative of no halogen flame retardant, the flame retardant mechanism generally consists of three parts, namely the carbon source (often polyhydroxy compounds, such as pentaerythritol), acid source (such as ammonium polyphosphate, APP) and foaming agent (such as melamine), which is by the interaction. And the formation of carbon layer:
(1) at lower temperature (150 or so, the specific temperature depends on the properties of acid source and other components), an acid source can produce esterified polyols and an acid that can be used as dehydrant.
(2) when the temperature is slightly higher than the temperature of releasing acid, the reaction of acid with polyol (Tan Yuan) is esterified, and the amine in the system is used as the catalyst of esterification reaction to accelerate the reaction.
(3) the system melts in the process of esterification or esterification.
(4) the non flammable gas produced by water vapor and gas source in the reaction process expands the system that has been in the state of melting and thawing. At the same time, polyols and esters are dehydrated and carbonized to form inorganic and carbon residue, and the system expands further.
(5) the reaction is close to completion, and finally form a gel curing system, porous carbon foam layer.
For halogen, many countries and organizations in the world are introduced according to a variety of halogens, green environmental protection agency of many non-governmental organizations are also actively promoting non halogenated action, while some large multinational companies and have formulated the corresponding environmental protection requirements, including Dell, HP, Apple, Intel, AMD, etc. the statement also imported halogen-free materials, thus non halogenated requirements has become a global trend of development.