Talk about TPE why is it so hard to do 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 plastic processing and wide processing methods.

TPE is mainly composed of two parts, one is plastic, as a continuous phase, and the other is rubber as a dispersed phase. Usually rubber needs to be matched with softening oil or plasticizer. Curing agents and some auxiliary auxiliaries are also essential. In addition, in order to reduce costs or improve certain performance, some inorganic fillers will also be added. According to the material composition, it can be divided into: styrenes (SBS, SIS, SEBS, SEPS), olefins (TP0, TPV), dienes (TPB, TPI), vinyl chlorides (TPVC, TCPE), urethanes ( TPU), esters (TPEE), amides (TPAE), organic fluorines (TPF), silicones and vinyls, etc., covering almost all fields of synthetic rubber and synthetic resins. The following lists several common TPE components.

However , there are many components in the TPE thermoplastic elastomer formulation system. Due to the differences in the structural properties of the components, the mechanism is not clear, which brings great difficulty to the flame retardant treatment, and there are also great hidden safety hazards during use, which gives TPE The use of the product brings certain limitations. So, what difficulties might be encountered in TPE flame retardant treatment ?

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 and wear resistance are greatly reduced, the melt fluidity becomes poor, and the elastomer is difficult Formed, and the surface is prone to migration of flame retardants, which constitutes a polluting environment.

The flame retardant mechanism is not clear

The TPS system is mainly a multi-phase mixed structure of rubber, polyolefin resin, plasticizer and filler. Although 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 are actually different. It is more difficult for one flame retardant to flame retard multiple plastic components at the same time.

Plasticizer reduces flame retardancy

In order to reduce the hardness of TPS, it is more soft to the touch, and often needs to add plasticizer ( white oil ) , usually 26 # , 32 # white oil, 70 # white oil, four kinds. Due to the difference in the limit oxygen index and fluidity of the four oils, and the natural flammability of oils greatly reduces the flame retardancy of elastomers, how to solve the relationship between plasticizers and flame retardancy when producing low hardness products? It is very important to choose the type of white oil.

Based on the difficulties that may be encountered above, what are the actual problems that flame retardant TPE may encounter during processing ? What are the corresponding solutions ?

Wire surface is not smooth

TPE wire processing often occurs, generally because the temperature is not adjusted well and the flame retardant is mixed unevenly. It may also be caused by incorrect mold selection. Of course, it has a great relationship with the material formula. Experienced processing manufacturers will eliminate equipment problems, and can find the right temperature after repeated debugging, but the selection of the right materials and specific formulas requires engineers to be cautious. It is recommended to communicate with raw material suppliers to know the material properties and processing precautions. Choosing the right material will get twice the result with half the effort ! The surface processing of TPU wire is better than that of TPE wire.

Wire surface precipitation

So far, no material can guarantee no precipitation at all, the specific precipitation performance is: the surface is white, oily or misty. With current technology, this problem has not been resolved. It is recommended that customers choose materials with a slightly white surface when choosing, this precipitation will not affect its physical properties and electrical performance. Do not use the material with oil on the surface, it is easy to fall off and peel during use. In addition, the precipitation is also important. The precipitation of good materials is slight, and it is not easy to occur in a short period of time. Even if it happens, it is just a light rub.

Scrape and peel off the surface

Whitening is caused by the addition of PP and PE in the material and can be improved. Some manufacturers have achieved that the products will not be blank, but TPE is more difficult than TPU . If the level of peeling and peeling the glue is very general, what I want to say here is the recipe !  Craft!

Processing difficulty

Elastic body is now working more slowly than PVC slower by about 50%. The temperature is not easy to adjust, and a lot of material must be wasted when adjusting the machine. In addition, the machine must be washed before making the material. The waste can be described as not small. These are inevitable. In production, sometimes everything in the first stage of production is normal, and there are problems in the post-processing. It needs to be explained here that the sub-licenses are risky and use caution.

Flame-retardant TPE / TPU is a very unique material. TPE / TPU flame-retardant problems still require everyone to do more work in the selection of materials, formulas and processes. In general, it is recommended to use liquid flame retardants to reduce hardness while improving flame retardancy, reducing the amount of powdered flame retardants, can improve the transparency of the product, and use compatibilizers to improve the compatibility of flame retardants and substrate Performance, improve precipitation and greatly improve mechanical properties ; adopt special screw distribution in the process to increase the dispersion of flame retardants in the system, improve flame retardant efficiency, and improve appearance ; adopt new silicone flame retardants, condensed phase flame retardant mechanism The cracked carbon layer with strong oxidation resistance improves the flame retardant efficiency.