Regarding the properties of TPE flame retardant materials, Dechuang Chemical Co., Ltd. will share with you below. TPE-S thermoplastic elastomer is usually a thermoplastic elastomer with SEBS (styrene-ethylene-butylene-styrene block copolymer) as the main substrate. It has both the processability of plastics and the physical properties of rubber, and is flexible and delicate in hand feeling, anti-aging, high in strength, very resistant to low temperature, relatively resistant to high temperature, relatively easy to form, not easy to flow, good in dimensional stability and design flexibility. It is suitable for plastic forming processes such as injection molding, extrusion, injection pressing, calendering, hollow forming, etc. Almost all soft products that do not need oil resistance, chemical solvent resistance and are not particularly resistant to high temperature can be used.
TPE-S can also be abbreviated as TPS, i.e. thermoplastic styrene elastomer, which generally does not contain SBS.
However, the thermoplastic elastomer TPE-S formula system has many components. The plastic phase can be PP, PE, PS, EVA, etc. The elastomer phase can be SEBS, SEPS, SEEPS, or polyolefin elastomer with POE, etc. Due to the difference in structural properties of each polymer component, the flame retardant mechanism is unclear, which brings considerable difficulty to flame retardant. Elastomers with poor flame retardant effect, which are used in some occasions with high flame retardant requirements, bring certain potential safety hazards, which bring certain limitations to the application field of thermoplastic elastomers.
Thermoplastic Elastomer TPE-S Flame Retardant Solution-Four Steps Principle
According to my years of research and development accumulation in Shanghai Rizhisheng Company, I am committed to overcoming the above technical difficulties, and have summarized the four-step principle, and achieved certain results. The flame retardant TPE-S elastomer can reach UL94 V0, oxygen index 27%, tensile strength greater than 12MPa, and elongation at break greater than 450%.
The following four-step principle is shared with friends who have been committed to flame retardancy of thermoplastic elastomers. Adherence to the four-step principle is believed to inspire everyone.
1. The liquid flame retardant not only reduces the hardness but also improves the flame retardancy, reduces the addition amount of the powder flame retardant, and can improve the transparency of the product;
2. Relying on Nantong Ri Sheng, a leading compatilizer enterprise in China, to develop a special compatilizer for SEBS flame retardant system to improve the compatibility of flame retardant and substrate, improve precipitation and greatly improve mechanical properties;
3. Special screw distribution is adopted in the process to improve the dispersion of flame retardant in the system, improve the flame retardant efficiency and improve the appearance;
4. A new type of silicone flame retardant is adopted, and a condensed phase flame retardant mechanism is adopted to form a cracking carbon layer with extremely strong oxidation resistance so as to improve the flame retardant efficiency.
Difficulties in flame retardancy of thermoplastic elastomer TPE-S
Difficulty 1: It is difficult to select flame retardant
Due to the low flame retardant efficiency of halogen-free flame retardant, another important reason is that the proportion of halogen-free flame retardant is usually relatively small, so if the same weight of flame retardant is added to the material, the volume proportion of halogen-free flame retardant in the material is larger. Therefore, too many flame retardants lead to poor compatibility with the substrate. The elastic modulus, flexibility, mechanical properties and wear resistance of thermoplastic elastomer TPE-S are greatly reduced, melt fluidity is deteriorated, elastomer is difficult to form, and flame retardant migration is easy to occur on the surface, thus polluting the environment.
Difficulty 2: unclear mechanism of flame retardant
The thermoplastic elastomer TPE-S system is mainly a multiphase mixed structure of styrene block copolymer elastomer, polyolefin resin, plasticizer and filler. Although there are relatively mature formulas and examples for halogen-free flame retardancy of polyolefin resins. However, SEBS, polyolefin PP and PE have different flame retardant mechanisms. It is difficult for one flame retardant to flame retardant multiple plastic components at the same time.
Difficulty 3: Plasticizer Reduces Flame Retardancy
Thermoplastic elastomer TPE-S usually needs to add plasticizers (linear paraffin oil, naphthenic oil, etc.) in order to reduce the hardness and make the hand feel softer. Generally, 26#, 32# white oil, 50# and 70# white oil are the four main types. Due to the difference in limiting oxygen index and fluidity of the four oils, and the natural flammability of oil substances greatly reduces the flame retardancy of elastomers, how to solve the relationship between plasticizer and flame retardancy in the production of low-hardness products and how to choose the type of white oil are very important.
Points for Attention in Combination of Flame Retardant Material Formulas
1. The difficulty of halogen-free flame retardant thermoplastic elastomer, but the so-called solution is of little value. First of all, liquid flame retardants usually have worse description than elastomers.
2. Compatible agents can indeed improve certain compatibility, but the strength of SEBS-g-mah will be much lower than that of conventional SEBS.
3. For manufacturers specializing in halogen-free flame retardant elastomers, screw combination is not a problem.
4. Silicone flame retardant, which sounds high and has low practical value.
