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Unilink® 4200 Chain Extender

For several decades, Dorf Ketal's Unilink® chain extenders have played an integral part in both the figurative and literal backbones of the global polyurethane and polyurea polymer markets. Unilink® 4200 chain extender has relatively low reactivity, making it an efficient polymer curing agent used in coatings, adhesives, sealants, and polymeric foam formulations based on TDI (toluene diisocyanate) and MDI (methylene diphenyl isocyanate). 

Polymers and foams cured with Unilink® 4200 show improved strength, higher hardness, increased adhesion, longer pot life, and better impact resistance and load-bearing properties. It has a unique difunctional aromatic diamine structure involved in building robust linear polymer networks. In many applications, Unilink® 4200 chain extender provides advantages in being easy to handle, environmentally friendly, and unreactive to moisture. In addition, it is broadly compatible with most polyols, co-curatives, and polyurethanes


Polyurea Systems

Unilink® 4200 improves gel time and flow properties and allows polyurea coatings to be processed by spraying or pouring. It also increases adhesion to substrates and bonding between coats and can improve surface finishes. When cured, polyurea systems gain excellent physical properties, improved impact resistance, and higher performance in low temperatures. 

Flexible Foams

In flexible foam applications, Unilink® 4200 improves tensile, tear, and load-bearing properties. For example, in standard TDI and high-resilience slabstock foam systems, which often have lower foam densities, Unilink® 4200 has been shown to significantly improve the load bearing and tear strength of polyester foam. It also softens and decreases the density of cold-molded foams. This produces foams with better tear and elongation properties, higher tensile strength, improved mold flow, and decreased demold times. 

Rigid Foams

Unilink® 4200 is highly useful in rigid foams, which show substantial improvement in compressive strength and dimensional stability. They also benefit from reduced friability, gain a higher percentage of closed cells, and exhibit a lower K-factor. In insulative material applications, this property leads to foams with better insulative performance and higher durability. Compressive strength is also enhanced by Unilink® 4200 chain extender, where polyisocyanurate foams can gain a 100% increase in compressive strength in addition to enhanced dimensional stability. 

Coatings, Adhesives, Sealants & Elastomers

Formulations that use Unilink® 4200 chain extender adhere better to substrates and develop smoother surface finishes. This is due to a relatively low viscosity that improves surface wetting and handling and facilitates better coverage. Unilink® 4200 also enables coatings based on TDI and MDI to be cured at ambient temperatures. 

ChemPoint is here to help you work with Unilink® 4200 in your polymeric foam or coating, adhesive, or sealant application. For more information or to request a sample of Unilink® 4200, click below. 

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