Three preparation methods of TPV

TPV preparation methods are usually three, namely dynamic vulcanization method, physical blending method, latex blending method. The ultimate purpose of the three methods is to obtain the classic "sea-island" structure of TPV. (EPT is EPDM in the figure below)

Basic process flow of TPV production:

1) High-speed mixing: It refers to the full mixing of different types of materials for the convenience of subsequent processing, usually using high-speed mixing pot for mixing.

2) Extrusion granulation: It is the process of adding the flake raw material produced by high temperature kneading to the auxiliary material mixing again, and the output of granular raw material. It does not involve the change of molecular structure, which is equivalent to the secondary mixing.

3) Vulcanized extrusion: the material by weight loss scale automatic feeding, after the twin screw extruder dynamic vulcanized extrusion, underwater granulation machine. In this process, the molecular structure of raw materials changes, which is the most core part of the entire production process.

4) Screening: remove too long, too short and other elastomer particles that do not meet the size requirements, and get elastomer particle products that meet the specified size.

5) Homogenization: The granular thermoplastic elastomer is sent into the homogenization bin to ensure the uniformity of materials in each bin.

Pic 1 Control phase reversal form control

1 Dynamic vulcanization

Dynamic vulcanization technology has undergone a long period of evolution, from the early open smelter process to the close smelter process, until the twin-screw continuous vulcanization manufacturing technology. It was first developed in 1973 by Uniroyal Company in the United States, which produced partially vulcanized thermoplastic elastomer, but the performance was poor. In the late 1970s, Coran et al. of Monsanto Company in the United States conducted systematic research on the dynamic full vulcanization blends of thermoplastics and elastomers, developed a dynamic full vulcanization production technology, and produced EPDM/PP and other thermoplastic elastomers (brand name "Santoprene"). Some properties of vulcanized rubber (such as heat resistance and low compression deformation) were successfully combined with the easy working properties of thermoplastics, so that thermoplastic elastomers really came to the market.

The technical characteristics of TPV prepared by dynamic vulcanization:

1) In the process of preparing fully vulcanized thermoplastic elastomers by dynamic vulcanization method, there should be appropriate temperature field and shear field, and the blending temperature must be higher than the melting point or softening temperature of the resin to ensure fluidity, but not too high, so as to avoid oxidative degradation. The shear field is the decisive factor of the particle size of the dispersed phase, and the particle size of the dispersed phase can be greatly reduced at high shear rate. At the same time, the type and amount of crosslinking agent, blending time and coordination between each other will affect the size and distribution of rubber phase, and then affect the performance of fully vulcanized thermoplastic elastomer, which puts forward extremely high requirements for blending equipment and preparation technology. Ordinary plastic processing equipment can not meet the requirements.

2) Coran et al. found that the size of rubber particles in thermoplastic elastomers has an effect on the tensile strength and maximum elongation. The tensile strength and elongation at break are inversely proportional to the diameter of rubber particles. The smaller the diameter of rubber particles, the better the mechanical properties. In the dynamic vulcanization method, because the dispersed phase rubber particles are generated by mechanical shear, the obtained rubber particle size cannot be very small.

3) Because the dynamic vulcanization method is to produce vulcanization at the same time of blending, blending must reach a certain residence time in mixing equipment, rubber phase can be completely vulcanized, so not only the production cycle is relatively long, and in the preparation process is easy to cause the degradation of rubber phase or plastic phase, thus limiting the development of new thermoplastic elastomer varieties.

2 Physical blending method
The typical example of preparing fully vulcanized thermoplastic elastomers by physical blending is a new method invented by Beijing Research Institute of Chemical Industry. Superfine all-vulcanized powder rubber prepared by radiation vulcanization was used as raw material, which was blended with thermoplastic in conventional rubber and plastic blending equipment, so as to obtain fully vulcanized thermoplastic elastomers. This radiation-vulcanized ultra-fine all-vulcanized powder rubber has a gradually decreasing crosslinking density from the outer surface of the rubber pellet sphere to the interior. In the phase structure formed by it and thermoplastic resin, the thermoplastic resin phase can be continuous phase and the rubber phase can be dispersed phase even if the volume fraction exceeds 50%. Due to the internal crosslinking structure of fully vulcanized powder rubber, a simple physical blending method was used to prepare fully vulcanized thermoplastic elastomers.

3 Emulsion blending method

As emulsion blending method is rarely used in practice, it is omitted here。

Conclusion

At present, dynamic vulcanization method is widely used in TPV production enterprises at home and abroad, but few enterprises use physical blending method to produce TPV。

Company Profile：ANHUI JINKE OPTA POLYMER CO.,LTD . (ANHUI OPTA) is a high-tech enterprise specializing in the research and development, production, sales and service of high performance thermoplastic elastomer, modified plastics, functional masterbatch and other products. Our team has been committed to the research, development, production and sales of thermoplastic elastomer and halogen-free environment-friendly flame retardant materials for more than 20 years. Currently, our TPV technology research and development capability and product market share rank among the forefront in China. Products cover TPV(EPDM/PP), TPO, TPE-S, TPU, TPEE, functional masterbatch and other varieties, widely used in a variety of auto parts, to help achieve automotive lightweight. If you have any technical questions about thermoplastic elastomer materials, please contact us (contact information: 0550-3915588/13655164088 Ms. Han, Website: https://www.optapol.com/).