The impact of TPU raw materials on product performance (Part 2) - Guangyuan Ruifeng New Materials

Category: TPU (popular science, no product)

Release Time: 2020-06-24

Summary: With the type of polyol oligomer determined, we also need to understand the impact of the molecular weight of the polyol oligomer on the performance of TPU. Under a fixed chemical ratio of raw materials, changing the molecular weight of the polyol oligomer has a significant impact on the performance of TPU. An increase in the molecular weight of the soft segment means a decrease in the proportion of hard segments. An increase in the proportion of soft segments leads to a decrease in strength, an increase in elasticity, and an increase in permanent deformation. Therefore, the molecular weight of the polyol oligomer is also an important factor to consider in the design of TPU formulations.

3、 Influence of Oligomeric Polyol Molecular Weight on TPU Properties （ TPU Crosslinking Agent Manufacturer ）

Having determined the type of oligomeric polyol, we also need to understand the influence of the oligomeric polyol molecular weight on the properties of TPU. With a fixed chemical ratio of raw materials, changing the molecular weight of the oligomeric polyol has a significant impact on the properties of TPU. Increasing the molecular weight of the soft segment reduces the proportion of hard segments. An increase in the soft segment proportion leads to decreased strength, increased elasticity, and increased permanent deformation. Therefore, the molecular weight of the oligomeric polyol is also an important factor to consider in TPU formulation design. (TPU Crosslinking Agent Manufacturer)

4、 Influence of Isocyanate on TPU Properties （ TPU Crosslinking Agent Manufacturer ）

Diisocyanates are smaller molecules, and they have two functions in TPU production. First, they act as coupling agents to connect macromolecular diol components, generating a sparse soft segment of polyurethane; they also act as coupling agents to connect small-molecule diol chain extender components, generating a dense hard segment of polyurethane; and they act as coupling agents to connect the soft and hard segments, forming the TPU chain. The second function of diisocyanate is its structural contribution to the physical properties of TPU, making the greatest contribution to the hard segment. (TPU Crosslinking Agent Manufacturer)

Here, we will mainly explain the typical diisocyanates used to synthesize TPU for reference when designing formulations. MDI has low vapor pressure, low toxicity, and good symmetry, and the resulting elastomer generally has higher strength than TDI-based elastomers. Commonly used 4,4'-MDI is a solid at room temperature. Some minor diisocyanates are also used in special cases to synthesize polyurethane elastomers. Elastomers synthesized from symmetrically structured PPDI and cyclohexane-1,4-diisocyanate (CHDI) have higher mechanical strength and heat resistance. NDI-based polyurethane elastomers have high fatigue resistance, especially excellent mechanical properties, dynamic properties, permanent deformation properties, and oil resistance, and are used in special automotive parts, etc. Elastomers made from IPDI and HDI have the characteristic of non-yellowing and can be used in some yellowing-resistant elastomers, etc. (TPU Crosslinking Agent Manufacturer)

5、 Chain Extenders and Crosslinkers （ TPU Crosslinking Agent Manufacturer ）

Many chain extenders are used for TPU, usually divided into two categories: diamines and diols. The main functions of chain extenders are as follows: Low molecular weight di-compounds can cause the polyurethane reaction system to undergo rapid chain extension or crosslinking. Secondly, they have characteristic groups that can chemically react with the reaction system, and they have low molecular weight and are highly reactive. In the entire reaction raw material system, they constitute a strong reaction competition probability with the isocyanate and polyol system, so they can very effectively regulate the reaction rate of the reaction system. In actual work, different types and amounts of crosslinking agents can be used to adjust process parameters such as the viscosity increase of the reactants to meet the requirements of the processing technology. ƒ The main role of chain extenders is to adjust the relevant properties of the product. They not only participate in the reaction and have chain extension and crosslinking effects, regulating the foam structure and porosity, improving the resilience, rigidity, and mechanical properties of the product, but also reducing the viscosity of the raw material components and improving the compatibility of the raw material components. (TPU Crosslinking Agent Manufacturer)

In actual production, selecting a suitable chain extender is crucial. The chain extender is closely related to the performance of TPU products. Given the different -NCO activity in isocyanate products, in order to control the reaction rate, in the preparation of TPU products, in addition to considering the influence of the chain extender on product performance, the reactivity with -NCO is also a key factor. (TPU Crosslinking Agent Manufacturer)

Keywords: The impact of TPU raw materials on product performance (Part 2) - Guangyuan Ruifeng New Materials

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