Inorganic flame retardant and nitrogen flame retardant TPU

1. Nitrogen flame retardant EVA

nitrogen-containing flame retardants mainly include three categories: melamine, dicyandiamide, guanidine salts (guanidine carbonate, guanidine phosphate, condensed guanidine phosphate and guanidine sulfamate) and their derivatives, especially phosphate derivatives. It is generally believed that after the thermal decomposition of nitrogen flame retardants, it is easy to release non-combustible gases such as ammonia, nitrogen, deep nitrogen oxides, and water vapor. The generation of non-combustible gases and the decomposition heat absorption of the flame retardant (including a part of the sublimation heat absorption of the flame retardant) take away most of the heat, greatly reducing the surface temperature of the polymer. Non-combustible gas, such as nitrogen, not only plays a role in diluting the concentration of oxygen and polymers in the air to generate combustible gas by thermal decomposition, but also reacts with oxygen in the air to generate nitrogen, water and depth of oxides, which can achieve good flame retardant effect while consuming oxygen on the surface of the material.
A large number of patents using melamine ureate as EVA flame retardant have been issued. For example, Japanese Patent 54-85242 discloses a resin composition containing 3% -33.3 (mass fraction, the same below) of melamine ureate. Chinese Patent 1639245A uses melamine cyanurate as EVA flame retardant, preferably in an amount of 35%-45%, and the content lower than 28% cannot meet the required flame retardancy, A content higher than 50% tends to reduce physical properties. The content of melamine cyanurate required to achieve flame retardancy is also affected by the type of TPU. Polyether EVA usually requires less melamine cyanurate than polyester TPU. U.S. Patent 5837760 discloses the use of organic phosphate alone or a mixture of organic phosphate and melamine urate as flame retardant for EVA. The mixture contains 35%-80% TPU and 3%-15% organic phosphate, 0 ~ 50% of melamine derivatives, good flame retardant effect, etc.
2. Inorganic flame retardant flame retardant EVA.
Due to the limitations of raw material cost, technological development, and use conditions, the mineral flame retardants currently used on a large scale are mainly aluminum hydroxide flame retardants and magnesium hydroxide (brucite) flame retardants. Aluminum hydroxide is the largest and most widely used mineral flame retardant in the world, accounting for about 45% of the total amount of flame retardant. Aluminum hydroxide used in domestic and foreign markets is mainly a-alumina trihydrate (ATH , a -Al2O3 · 3H2 O). Magnesium hydroxide is another environmentally friendly flame retardant after aluminum hydroxide. The United States is the country with the largest output and most varieties of magnesium hydroxide flame retardants. China has abundant magnesium hydroxide resources, but magnesium hydroxide flame retardants are studied late. The output, scale, variety and quality have been significantly behind the international level.
For inorganic flame retardants, in order to achieve high flame retardant effect, it is necessary to increase the amount of flame retardant, and inorganic materials are usually poor compatibility with polymer matrix, a large number of mechanical and thermal properties of EVA materials will cause a lot of adverse effects. In order to improve the compatibility, it is necessary to carry out appropriate surface treatment of the inorganic flame retardant.
Pint et al. [59] added mica and ATH together as additives to polyurethane materials. ATH has obvious flame retardant effect, but it reduces the tensile strength and hardness of the materials. Mica has good thermal insulation effect, and after compounding with ATH, it can partially compensate for the negative impact of ATH on the mechanical properties of EVA materials,