With the increasingly widespread application of flammable polymer materials, the demand for flame retardants has greatly increased.
Compared with organic flame retardants, inorganic flame retardants have the advantages of low production cost, high flame retardant efficiency and low environmental pollution, etc. However, inorganic flame retardants have low compatibility with polymer materials, have a great impact on the mechanical properties of materials, and usually must be modified to achieve a better flame retardant effect. Therefore, the search for effective improvement of the compatibility of flame retardants and the promotion of good modification methods is the necessary research for the development of inorganic flame retardants.
At present, the main varieties of inorganic flame retardants are aluminum hydroxide, magnesium hydroxide, inorganic phosphorus compounds, borates, antimony oxide, molybdenum compounds, etc. The most researched flame retardant modification methods of magnesium hydroxide are flame retardant microencapsulation, flame retardant ultra-fine, flame retardant surface modification.
I. Microencapsulation of flame retardants magnesium hydroxide
Microencapsulation technology refers to the use of polymer materials wrapped solid, gas or liquid into a tiny capsule with a shell and core structure of 1 μm to 5000 μm in diameter. The characteristics of microencapsulation technology are that microcapsules can morphologically transform liquids and gases into solids, giving the core material new physical properties; the capsule wall can play a role in isolation and protection, allowing the stable coexistence of substances that can easily react with each other, while shielding colored, tasty or toxic substances; the core material can be released in a controlled manner as needed.
The main preparation methods of flame retardant microcapsules include interfacial polymerization, in situ polymerization, phase separation, solution evaporation, sol-gel method, etc.
2. flame retardants ultra-fine
Nanoscale flame retardant is a block, film, multilayer film and fiber-like flame retardant coalesced from ultra-micro flame retardant particles with particle size of 1 nm to 100 nm. After the traditional inorganic flame retardant materials are treated by hyperfining, the size effect and surface effect of nanoparticles are used to enhance the interfacial effect, so that the flame retardant can be more uniformly dispersed in the matrix resin and play the role of rigid particle plasticization and enhancement, improving The compatibility of flame retardant and polymer matrix is improved, and the impact resistance and flame retardant performance of the material are improved.
In recent years, the study of flame retardant ultra-fine modification of scholars in the traditional gas phase preparation method, liquid phase preparation method, high-energy mechanical ball milling method based on continuous innovation, research and invention of more and more flame retardant ultra-fine modification methods.
Due to the high flame retardant efficiency of nano flame retardant system, and non-toxic and environmental protection, its compounding and synergy with other flame retardants has become one of the hot spots of nano flame retardant.
3. Surface modification of flame retardants magnesium hydroxide
Surface modification is the use of physical or chemical methods, the use of surface modifiers on the surface of the particle chemical reaction and surface coating, so as to change the chemical and physical properties of the particle surface process. There are many methods of flame retardant surface modification, which can be divided into coupling agent modification and organic modification in terms of modifier, and dry and wet process.
Coupling agent is a typical modifier, its molecules contain hydrophilic groups and hydrophobic groups, hydrophilic groups and inorganic powder surface chemical reaction and make inorganic powder surface covered with a layer of organic film, reduce the surface energy of inorganic powder, change its hydrophilic surface properties; hydrophobic groups can react with polymer materials or entanglement, inorganic powder and polymer materials between the role of the bridge, so that inorganic powder firmly bonded in the polymer.
Common coupling agents are silane coupling agent, aluminate coupling agent and titanate coupling agent.
At present, the consumption of flame retardants has jumped to the second place of plastic additives, although people are still developing new varieties of inorganic flame retardants, such as tin compounds, key compounds, iron, expanded graphite, etc., and there has been some development, but the focus of work for some time in the future is still on the modification of aluminum hydroxide and magnesium hydroxide and other metal hydroxide inorganic flame retardants, compounding as the center, and constantly improve its impact on the material The impact of physical and mechanical properties, especially the development of high-efficiency synergists, and promote the development of inorganic flame retardants to the direction of high efficiency and functionalization.