Halogens introduction

Halogens are a series of elements from Group 17 IUPAC Style (formerly: VIIA) of the periodic table, comprising fluorine, chlorine, bromine, iodine, and astatine among which astatine is a radioelement and hardly exists in products. The former four elements exist in products, especially in polymeric materials as organic compounds. Halogen compounds currently are used in products as flame retardant: PBB, PBDE, TBBP-A, PCB, Hexabromocyclododecane, Tribromophenol, short-chain chlorinated paraffin; as ozone damaging substances to refrigerant, insulation material: CFCS、HCFCs、HFCs etc.

Adding halogens (F, Cl, Br, I) in plastic can increase the ignition point. For its advantage, the ignition point is about 300 ℃ which is higher than ordinary polymeric materials . It will emit halogenated gas (F, Cl, Br, I) and absorb oxygen rapidly to extinguish the fire. But for its weakness, visibility caused by high concentration chlorine will result in failure to identify escape exit, meanwhile chlorine is toxic and affects respiratory system. In addition, when halogenated gas, releasing from burning polymeric halogen, combines with water vapor, it will generate harmful corrosive gas (hydrogen halide) which corrodes some equipment sand structures.                                                          

Brominated flame retardants PBB, PBDE, TBBPA is now mostly used in electrical and electronic industries including circuit boards, computers, fuel cells, televisions and printers etc. Dioxin generated by burning halogen flame retardants can exist in the environment for many years, and even permanently accumulates in the organism.
     
     Harmful ultraviolet absorbed by the ozone layer will break down CFCs, releasing chlorine atom and separating ozone molecules to free oxygen molecule and dichlorine monoxide molecule, thereby destroying ozone molecules. One achlorine atom can destroy over 100,000 ozone molecules, which will greatly increase risk of skin cancer, cataracts and other eye diseases and have disastrous effects. In addition it may result in food disasters, aquatic organism shortage, and formation of "greenhouse effect" (atmosphere warming).
     
      Therefore, many large international companies are promoting complete abolition of halogen containing materials, such as halogen flame retardants used in products

At present, different non-halogenated products have different limits. For halogen-free wire and cable, the limit is 50ppm (in accordance with regulation PREN 14582); after combustion content of hydrogen halide should be less than100ppm( in accordance with regulation EN 5067-2-1)and pH value of hydrogen halide in water should be equal to or more than 4.3 (weak acid) (in accordance with regulation EN-50267-2-2); after products combustion in a closed container light transmittance should be equal to or more than 60% (in accordance with regulation EN-50268-2). content of halogen-free PCB, bromine, chlorine should be less than 900ppm and (bromine + chlorine) should be less than 1500ppm.

Halogen test items：F、 Cl 、Br、I、At