Shanghai Risheng Technology Co., Ltd.

As an important standard for electronic and electrical components, the UL94 flame retardant standard stipulated by UL Laboratory in the United States is widely known, but the evaluation method mainly evaluates the combustion performance of the sample in direct contact with the flame, which is a passive flame retardant safety index. In recent years, the internal plastic parts of electronic and electrical equipment in the use of the process due to poor contact, overload, short circuit and overheating active fire caused by the fire is frequent. Based on this background, the International Electrotechnical Commission has greatly strengthened the flame retardancy standard and requires the industry to implement more stringent glow wire flame retardancy test standards, that is, it is required that the flame retardancy of plastic parts used in long-term unattended electrical appliances must meet UL 94 V-0 level and 750 ℃ glow wire contact material within 30 seconds without ignition or burning time less than 5s, that is, glow wire ignition temperature (GWIT) greater than 750 ℃; for specific components such as connectors, contact switches, motors and circuit breaker housings, GWIT temperatures greater than 850°C and Glow Wire Flammability Index (GWFI)950°C are also required. The flame retardant reinforced PBT material developed by the industry recognized as the most effective bromine antimony flame retardant technology has been unable to meet such high glow wire requirements.

Compared with the UL94 flame retardant standard, the technical difficulty of increasing the GWIT temperature of flame retardant materials has risen sharply, because the influence factors of GWIT temperature involve the synergistic effect of solid phase flame retardant and gas phase flame retardant, and the single aspect of flame retardant can not meet the GWIT requirements. The key to improving GWIT is to quickly convert the surface of the plastic in contact with the glow wire into a protective layer of heat insulation, oxygen insulation and smoke suppression, covering and protecting flammable plastics, and delaying or even preventing them from being ignited by high temperature sources. We use solid-phase and gas-phase flame retardant mechanism, through the compound technology independent development to improve GWIT flame retardant synergistic agent, the application of the synergistic agent successfully developed 850 degrees C hot wire resistance of ultra-high grade flame retardant reinforced PBT material, the following brief analysis of the synergistic agent on the flame retardant enhanced modified PBT performance.

(1) The effect of the synergist on the GWIT properties of flame retardant reinforced PBT materials.

As can be seen from the above figure, the GWIT temperature of flame retardant reinforced PBT material gradually increases with the increase of synergist content, from 725 ℃ for ordinary flame retardant to 870 ℃ for adding 12% content, which is far higher than IEC's requirement of GWIT>750 ℃ for long-term unattended electrical plastic parts, and meets the ultra-high requirement of GWIT>850 ℃ for specific components such as connectors, contact switches, motors and circuit breaker housings.

(2) The effect of the synergist on the fluidity of flame retardant reinforced PBT materials.

With the increase of the content of the flame retardant synergist, the fluidity of the material gradually increased, from 45g/10min without adding to 75.2g/10min, an increase of about 65%. The improvement of fluidity improves the processing performance of the material, reduces the injection temperature, improves the injection efficiency, and saves energy consumption.

(3) The effect of the synergist on the physical and mechanical properties of flame retardant reinforced PBT materials.

The influence of the synergistic flame retardant on the mechanical properties of the material is divided into two aspects: first, with the increase of the content of the synergistic agent, the tensile and bending strength of the material shows a downward trend. when the addition amount is 5%, the tensile strength and bending strength only decrease within 15%, while at this time it reaches GWIT>750 ℃, but the impact strength increases by about 40%, in other words, the toughness of the material is more excellent, the physical and mechanical properties can fully meet the practical application requirements of the product. On the other hand, its impact performance shows a trend of increasing first and then decreasing. When the synergist content is 10%, its impact strength increases by about 20%, but its tensile and bending strength decreases by about 20%, and its GWIT can reach 855 ℃, so it is suitable for non-load-bearing parts with stricter GWIT requirements.

So far, ultra-high glow wire flame retardant reinforced modified PBT material has been highly recognized by the market and is widely used in timer housings, motor fans, connectors, coil frames and other components, and the material has independent intellectual property rights: patent name "high glow wire environment-friendly flame retardant reinforced PBT composite material and its preparation method" (publication number: 102040807A).