TPU Synthesis and Processing - Guangyuan Ruifeng New Materials

Category: TPU (popular science, no product)

Release Time: 2020-06-16

Summary: TPU stands for thermoplastic polyurethane, a type of polyurethane that can be plasticized by heating and dissolved by solvents. Compared to blended and cast polyurethanes, thermoplastic polyurethanes have few or no chemical crosslinks in their chemical structure; their molecules are essentially linear, yet there is a certain amount of physical exchange.

TPU stands for thermoplastic polyurethane, a type of polyurethane that can be plasticized by heating and dissolved by solvents. Compared to blended and cast polyurethanes, thermoplastic polyurethanes have little or no chemical crosslinking in their chemical structure; their molecules are essentially linear, yet they exhibit a certain amount of physical exchange. (TPU crosslinking agent, crosslinking agent manufacturer, PVC adhesion promoter)

The concept of physical exchange was first proposed by Schollenberge C.S. in 1958. It refers to the presence of reversible "connection points" between linear polyurethane molecular chains upon heating or exposure to solvents. These points are not actually chemical crosslinks, but they function as such. Due to this physical crosslinking, polyurethanes form a multiphase morphology structure. Hydrogen bonds in the polyurethane strengthen this morphology and enable it to withstand higher humidity.

I. Synthesis of TPU

Although TPU has many classifications, from a molecular structure perspective, it belongs to polyurethanes. So, how is it polymerized? Based on different synthesis processes, it is mainly divided into bulk polymerization and solution polymerization.

In bulk polymerization, it can be further divided into prepolymer methods and one-step methods depending on whether a pre-reaction is involved: The prepolymer method involves reacting diisocyanate with a macromolecular diol for a certain period of time, then adding a chain extender to produce TPU; the one-step method involves simultaneously mixing a macromolecular diol, diisocyanate, and a chain extender to react and form TPU.

Solution polymerization involves first dissolving diisocyanate in a solvent, then adding a macromolecular diol to react for a certain time, and finally adding a chain extender to produce TPU. (TPU crosslinking agent, crosslinking agent manufacturer, PVC adhesion promoter)

The type, molecular weight, and hard or soft segment content of the TPU soft segment, as well as the TPU aggregate state, will affect the density of the TPU, which is approximately between 1.10 and 1.25, showing no significant difference from other rubbers and plastics. At the same hardness, the density of polyether-type TPU is lower than that of polyester-type TPU.

II. TPU Processing

The synthesized TPU particles need to undergo various processing methods to form the final product. The main processing methods for TPU are melt processing and solution processing.

Melt processing uses commonly used processes in the plastics industry, such as mixing, calendering, extrusion, blow molding, and molding (including injection, compression, transfer, and centrifugal molding); solution processing involves dissolving the granules in a solvent or directly polymerizing in a solvent to form a solution, which is then used for coating, spinning, etc.

The production of TPU final products generally does not require a vulcanization crosslinking reaction, which can shorten the production cycle, and waste materials can be recycled and reused. (TPU crosslinking agent, crosslinking agent manufacturer, PVC adhesion promoter)

Keywords: TPU Synthesis and Processing - Guangyuan Ruifeng New Materials

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