Important raw material for polyurethane – Poly EPS

文: 馮子驊 / 聚和國際技術開發組 主任

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About Poly-EPS

Poly-EPS is a Polyetheramine sulfonic acid type chain extender, the amines in the chemical structure react with isocyanate groups during the synthesis of aqueous polyurethane dispersions to introduce sulfonic acid groups into the polyurethane segment, furthermore, to improve the storage stability and freeze-thaw stability of the polyurethane resin, and endow the polyurethane resin (PU) with antistatic ability.

Polyurethane (PU) applications and future trends

The polyurethane have nice adhesion, wear resistance and other material properties, so it’s widely used in various industrial and civilian products manufacturing fields, such as adhesives, coatings, synthetic leather, and medical equipment.

With increasing environmental awareness in recent years, the conventional solvent-based polyurethane has been gradually shifted to the development and application of water-borne polyurethane, and the production process of waterborne polyurethane has also been gradually changed from the acetone method (that requires a large amount of organic solvent) to the prepolymerization method (that only requires a low amount of organic solvent), also the mainstream.

What is a waterborne polyurethane (PU) chain extender?

A water-borne PU chain extender plays an important role in polyurethane prepolymerization process, precisely, to increase the hydrophilicity and emulsifying ability of water-borne polyurethane by introducing hydrophilic groups into the polyurethane structure.

At present, the most commonly used water-borne PU chain extenders are carboxylic acid type and sulfonic acid type, and the introduction of these two types of chain extenders would contribute to different effects on the mechanical properties of the finished water-borne polyurethane resins.

Carboxylic acid type V.S. Sulfonic acid type

1. Carboxylic acid type water-based chain extenders:

The polyurethane resins made from carboxylic acid type chain extenders usually have higher flexibility after film formation, but due to its poor hydrophilicity, the prepared emulsions have high viscosity, and the solid content of its water-borne PU resin is usually low.

2. Sulfonic acid type water-based chain extenders:

Due to their strong hydrophilicity, sulfonic acid type chain extenders can make water-borne PU resins with high solid content, relatively higher water-resistance after film formation and mechanical strength, the application range of such PU resins is relatively wider.

Sulfonic acid type and Poly-EPS

Compared with carboxyl chain extenders such as DMPA and DMBA, which prepared emulsions have better resistance to water and hydrolysis, the excellent hydrophilicity of the sulfonic acid group enables Poly-EPS to be added to IPDI system, TDI system and MDI system to prepare water-borne polyurethane emulsions with high solid content and high stability.

Poly-EPS has a larger molecular weight than other types of chain extenders, so the prepared polyurethanes have better softness and toughness, and its good compatibility can further reduce the amount of acetone used in the process and achieve the purpose of reducing waste generated during the process.