Talk about why TPE is so difficult to make flame retardant
Thermoplastic elastomer TPE (Thermoplastic Elastomer), also known as synthetic rubber or synthetic rubber. Its products not only have the high elasticity, aging resistance and oil resistance of traditional cross-linked vulcanized rubber, but also have the characteristics of convenient processing and wide processing methods.
TPE is mainly composed of two parts, one is plastic, as the continuous phase, and the other is rubber as the dispersed phase. Usually the rubber needs to be combined with a softening oil or plasticizer. Vulcanizing agents and some auxiliary auxiliaries are also essential. In addition, in order to reduce costs or improve performance in some aspects, some inorganic fillers will also be added. According to the material composition, it can be divided into: styrene (SBS, SIS, SEBS, SEPS), olefins (TP0, TPV), diene (TPB, TPI), vinyl chloride (TPVC, TCPE), urethane ( TPU), esters (TPEE), amides (TPAE), organofluorines (TPF), silicones and vinyls cover almost all areas of synthetic rubber and synthetic resins. The following are some of the common components of TPE.
However, the TPE thermoplastic elastomer formulation system has many components. Due to the structural properties of each component, the mechanism is not clear, which brings great difficulty to the flame retardant treatment. There is also a great safety hazard in the use process, which gives TPE The use of the product brings certain limitations. So, what difficulties can TPE flame retardant treatment encounter?
Flame retardant selection is difficult
The flame retardant has poor compatibility with the substrate. When the amount of the flame retardant added in the elastic system is slightly larger, especially in the halogen-free flame retardant, the TPS elastic modulus, flexibility, mechanical properties, wear resistance are greatly reduced, the melt fluidity is deteriorated, and the elastomer is difficult to be used. Forming, and the surface is prone to migration of flame retardant, posing a polluted environment.
The mechanism of flame retardant is not clear
The TPS system is mainly a multiphase mixed structure of rubber, polyolefin resin, plasticizer and filler. The halogen-free flame retardant of polyolefin resin has relatively mature formulations and examples. However, the flame retardant mechanism of SEBS and polyolefin PP and PE is not the same. It is difficult for a flame retardant to flame retard a variety of plastic components at the same time.
Plasticizer reduces flame retardancy
In order to reduce the hardness, TPS is softer in hand, and it is often necessary to add a plasticizer (white oil). Generally, it is mainly composed of 26#, 32# white oil and 70# white oil. Due to the difference in limiting oxygen index and fluidity of the four oils, and the natural flammability of the oily materials greatly reduces the flame retardancy of the elastomer, how to solve the relationship between plasticizer and flame retardant in the production of low hardness products, how to It is important to choose the type of white oil.
Based on the difficulties that may be encountered above, what are the practical problems that the flame retardant TPE may encounter during the processing? What is the corresponding solution?
Wire surface is not smooth
TPE wire processing often occurs, usually due to the temperature is not adjusted and the mixing of the flame retardant is not uniform, or it may be caused by improper selection of the mold, of course, has a great relationship with the material formulation. Experienced processors will eliminate equipment problems and can find the right temperature after repeated debugging, but engineers should be cautious when choosing the right materials and specific formulations. It is recommended to communicate with raw material suppliers, know the material properties and processing precautions, and choose the right materials, it will do more with less! TPU wire will be better than TPE wire surface processing.
Wire surface precipitation
No material has been guaranteed to be completely precipitated so far, and the specific precipitation is as follows: the surface is white, oily or foggy. In the current technology, this problem has not been solved. Customers are advised to choose a material with a slightly white surface when selecting. This precipitation will not affect its physical properties and electrical performance. Do not use materials that are oily on the surface. It is easy to fall off and peel off during use. In addition, there are also some weights in the precipitation. The precipitation of good materials is slight, and it is not easy to occur in a short period of time, even if it is rubbed by hand.
Surface scratching and peeling off the glue
Scratch is caused by the addition of PP and PE to the material and can be improved. There are also some manufacturers that do not cover the product, but TPE is more difficult than TPU. If the level of peeling off the glue is very general, here is the recipe! Craft!
Elastomers are slower in processing and are about 50% slower than PVC. The temperature is not well adjusted, and a lot of materials are wasted when adjusting the machine. In addition, washing the machine before cooking, waste is not small. These are inevitable. In production, there are occasions when everything in the front stage is normal, and problems in the post-processing are problematic. In this case, it is necessary to explain that the sub-board material is risky and should be used with caution.
Flame-retardant TPE/TPU is a very unique material. The TPE/TPU flame-retardant problem still requires more work in material selection, formulation and process. In general, it is recommended to use a liquid flame retardant to reduce the hardness while improving the flame retardancy, reduce the amount of powder flame retardant added, improve the transparency of the product, and use the compatibilizer to improve the compatibility of the flame retardant with the substrate. Sex, improve precipitation and greatly improve mechanical properties; use special screw distribution to improve the dispersion of flame retardant in the system, improve flame retardant efficiency, improve appearance; adopt new silicone flame retardant, condensed phase flame retardant mechanism, form Highly resistant to cracking carbon layer to improve flame retardant efficiency.