Way to achieve flame retardancy
Gas phase flame retardant mechanism: that is, inhibiting the freedom of chain growth in the combustion reaction, and exerting flame retardancy effect.
Condensed phase flame retardant mechanism: it prevents the thermal decomposition of polymers in the solid phase and prevents the release of polymers Effect of flammable gases.
Interrupt heat exchange mechanism: that is, the heat generated by the polymer is taken away without feedback to the polymer, so that Polymers no longer break down constantly.
Flame retardant classification
According to the type of elements, they are divided into halogen series, organic phosphorus series and halogen-phosphorus series, nitrogen series, silicon series, Aluminum-magnesium series, molybdenum series, etc. According to the flame retardant effect, they are divided into intumescent flame retardants, char-forming flame retardants, etc. According to the chemical structure, they are divided into inorganic flame retardants, organic flame retardants, polymer flame retardants, etc. According to the relationship between flame retardants and the material to be flame-retardant, they can be divided into additive flame retardants and reactive flame retardants. Reactive flame retardants participate in the chemical reaction of polymers.
1. Halogen flame retardants
Halogen flame retardants are currently the most produced organic flame retardants in the world one. Halogen flame retardants are mainly used in the electronics and construction industries. About 50 to 100 kinds of halogen-containing flame retardants cover most market demands.
The reason why halogen flame retardants have attracted people’s attention is mainly because of their high flame retardant efficiency. , the price is moderate, and its performance-price ratio is difficult to compare with other flame retardants. In addition, there are many varieties of halogen flame retardants and they have a wide range of applications, so they are favored by people. However, halogen flame retardants generate more smoke and corrosive gases when thermally decomposed or burned, and are troubled by dioxin problems.
More than 80% of halogen-containing flame retardants are used in electronics/office equipment and construction industries. The main application varieties are: Styrenics and their copolymers, thermoplastic engineering plastics and epoxy resins.
2. Phosphorus-containing flame retardants
<p style="margin: 0px; padding: 0px; list-style: none; border: 0px; font-family: Microsoft YaHei, Arial, "Microsoft YaHei&And wall panels, etc.
In terms of thermoplastics, there is growing concern, especially in Europe, due to the environmental impact of halides. Aluminum hydroxide is receiving more and more attention. Its application scope is also getting wider and wider. In soft and hard PVC, ethylene-propylene rubber, EPDM, EVAC, ethylene-ethyl acrylate copolymer, PE-LD, PE-HD, mixtures of PE and PP, plastics made using cyclohexane catalytic technology, etc. In addition, it is also widely used in wires and cables, conduits, pipes, adhesives, laminates for construction, and thermal insulation foam.
Aluminum hydroxide can provide a lower smoke formula. Compared with formulas containing mixtures of halides and antimony oxides, this formula has low smoke toxicity and is less corrosive. Depending on the polymer and requirements, the mass fraction of aluminum hydroxide is 5% to 75%. In non-halogen systems, it is generally 35% to 65%. In this application range, the viscosity of the mixture sometimes increases and has a negative impact on the physical properties of the resin. Negative impact. Using appropriate additives and reasonable stirring technology can fully disperse aluminum hydroxide and greatly reduce the above effects. Proper surface treatment of aluminum hydroxide can also reduce the impact of high filling rates, which may increase the cost of the material.
Magnesium hydroxide
Magnesium hydroxide is the second largest-selling inorganic hydroxide flame retardant. It is a white to light white crystalline powder with relative density and Mohs hardness. When heated to above 450°C, weight (mass fraction) is lost due to loss of water.
When magnesium hydroxide is used as a flame retardant, its purity requirements are quite high. It contains at least magnesium hydroxide and many Level higher than. Most flame retardant grades are white powders with particle diameters ranging from μm. The surface area is 7~15 square meters/g. Most magnesium hydroxides used as flame retardants are surface treated to improve their dispersion and distribution in the polymer. Magnesium hydroxide, like aluminum hydroxide, is used in a higher addition amount, generally 50% to 70%. Magnesium hydroxide is more expensive than precipitated grade aluminum hydroxide due to high purity requirements and surface treatment requirements.
Magnesium hydroxide is used for thermoplastic plastics and thermosetting resins with a processing temperature of 200~225℃. Mainly used in EVAC, PP and blends, ABS and blends, fluoropolymers, PPE and blends, polyimide, etc. Not for use with thermoplastic polyester. Magnesium hydroxide is used together with aluminum hydroxide to meet different usage requirements. Magnesium hydroxide is also used in wires and cables, racks, building multi-layer boards, pipes, electrical appliances and other parts.
4. Silicon compound
Silicon compounds are new flame retardants. It can exert its flame retardant effect completely independently of halogen and phosphorus compounds. Recent articles and patents about silicone flame retardants have become a new hot topic. All silicones of various compositions have been studied as flame retardants. Silicon-containing compounds have obvious flame retardant effects whether they are used as additives to polymers or blends with polymers.
Practical silicon-containing compound flame retardant technologies include:
1) Through grafting reaction, silicon atoms or silicon groups are introduced into the polymer;
2) Add silicone powder;
3) Add high molecular weight silicone oil, organic metal compounds, and white carbon black;
4) Silicone rubber and metal compounds are used together;
5) Polymer/clay nanocomposite;
6) Add main silicate;
7) Use silica gel and potassium carbonate together;
8) Silicon-containing low melting point glass.
Silicon-containing flame retardants and their flame retardant technology have been extensively studied. Silicon-containing flame retardants have high Polymers are highly smoky and non-toxic, have low combustion calorific value and slow flame propagation, so they have attracted much attention. Their development potential and application prospects are very huge and broad.
, Arial, “Microsoft YaHei”; font-size: 14px;”>1) Passed Grafting reaction, introducing silicon atoms or silicon groups into polymers;
2) Add silicone powder;
3) Add high molecular weight silicone oil, organic metal compounds, and white carbon black;
4) Silicone rubber and metal compounds are used together;
5) Polymer/clay nanocomposite;
6) Add main silicate;
7) Use silica gel and potassium carbonate together;
8) Silicon-containing low melting point glass.
Silicon-containing flame retardants and their flame retardant technology have been extensively studied. Silicon-containing flame retardants have high Polymers are highly smoky and non-toxic, have low combustion calorific value and slow flame propagation, so they have attracted much attention. Their development potential and application prospects are very huge and broad.
