Selection of Raw Material for Environmentally Friendly Halogen - free Flame Retardant Heat Shrinkable Tube
作者:admin 新闻来源:深圳市普瑞曼材料科技有限公司 添加时间:2017-07-10
1, matrix resin selection
Environmentally friendly halogen-free flame retardant heat shrinkable tube with EVA and LDPE as the matrix resin, EVA (VA content of 28%) has good physical and mechanical properties, weather resistance, stress cracking resistance, good processing, you can add a lot of filler. With the VA content increased, its flexibility, flexibility, compatibility, transparency and other corresponding increase; when the VA content decreased, the performance close to the polyethylene. Therefore, the choice of VA content of 28%, melt flow rate of 3 ~ 5g / 10min EVA, to meet the environment-friendly halogen-free flame retardant heat shrinkable tube on the matrix resin requirements. LDPE has excellent resistance to low temperature performance (minimum temperature up to -70 ~ -100 ℃), mechanical properties and chemical stability, resistance to most of the acid-base erosion, at room temperature insoluble in general solvents, water absorption, electrical insulation Excellent performance, and EVA (VA content of 28%) compared to low prices, according to the requirements of environmentally friendly halogen-free flame retardant heat shrinkable tube, the choice of melt flow rate of 2 ~ 3g / 10min LDPE. EVA and LDPE mixing ratio of 7: 3, so that both play a low cost of LDPE, rigid and good characteristics, but also to improve the processing performance of mixed resin.
2, flame retardant choice
Environmentally friendly halogen-free flame retardant heat shrinkable tube with microcapsules red phosphorus and magnesium hydroxide as flame retardant. Ordinary red phosphorus in the air is easy to moisture, oxidation, and polymer materials, poor compatibility, and easy to cause an explosion, so its scope of application has been limited; microcapsules red phosphorus in addition to overcome the inherent shortcomings of red phosphorus, but also has high efficiency, Smoke, in the processing does not produce toxic gases, etc., its dispersion, physical and mechanical properties, thermal stability and flame retardant properties are improved and improved. Microcapsules red phosphorus heat decomposition into highly dehydrated metaphosphoric acid, it can make the burning of polymer surface carbonization, carbonization layer can not only prevent the release of combustible gas, but also with endothermic effect. In addition, micro-capsule red phosphorus and oxygen to form PO free radicals into the gas phase, you can capture a large number of H and HO radicals, play a role in flame retardant. After the magnesium hydroxide is heated (340 to 490 ° C), the surface heat is absorbed and the heat of the surface of the combustor is absorbed, and a large amount of oxygen on the surface of the diluted diluent of the combustion is released. The decomposition of the activated magnesium oxide adheres to the surface of the combustible Which prevents the combustion from proceeding, and the magnesium hydroxide does not produce any harmful substances in the whole flame-retardant process, and its decomposition products can also absorb the harmful gases and fumes generated by the combustion of the macromolecules at the same time, so that the combustion Quickly stop, while eliminating smoke, to prevent droplets.
It can be seen from the experiment that with the increase of the amount of red phosphorus in the microcapsules, the oxygen index increases and the flame retardant effect is obvious. However, due to the limitation of the processing technology, the particle size of the microcapsule red phosphorus is larger than that of the matrix material Poor, resulting in a rapid decline in tensile strength. The same time as the above-
With the increase of the amount of magnesium hydroxide, the oxygen index increased correspondingly. When the magnesium hydroxide was more than 90 parts, the oxygen index increased rapidly, indicating that the magnesium hydroxide reached a certain dosage, the flame retardant effect was obvious.
When the microcapsule red phosphorus and magnesium hydroxide in EVA / LDPE (70/30) in the common flame retardant, microcapsule red phosphorus and magnesium hydroxide has a synergistic flame retardant effect, compared with the use of flame retardant effect is obvious. When the amount of microcapsule red phosphorus is 15 parts, the amount of magnesium hydroxide reaches 90 parts, the oxygen index is more than 34%, can be through the VW-1 combustion experiment, but the tensile strength is low, can not meet the UL224 standard (≥10.4 MPa) Of the requirements, indicating that the matrix resin and flame retardant compatibility is not good. The same time as the above-
3, the role of compatibilizer
According to the characteristics of EVA, LDPE matrix resin, microcapsule red phosphorus and magnesium hydroxide, self-made compatibilizer to improve the compatibility of matrix resin and flame retardant. Add the compatibilizer, when the product ratio: EVA / LDPE 70/30), from the test data can be seen in the case of the same amount of flame retardants, adding compatibilizer, the increase in the matrix Resin and flame retardant compatibility, product tensile strength greatly improved. When the microcapsule red phosphorus 15, magnesium hydroxide 90, compatibilizer for 3 copies, the product of the flame retardant and tensile strength to meet the UL224 standard requirements. When the addition of 3 compatibilizers, the oxygen index has declined, but can pass the UL224 flame retardant VW-1 experiment.