Mechanism of Polyurethane Chain Extenders
Polyurethanes are polymers with urethane bonds made mainly from isocyanate and polyol. By using diamine monomers as chain extenders in isocyanate-terminated prepolymers, it is possible to introduce urea bonds in the main chain and impart various physical properties.
Recommended Applications of MXDA and 1,3-BAC
(Reference) Abbreviations and structural formulas of diamine monomers
Due to their high reactivity with isocyanates, MXDA and 1,3-BAC are recommended for use as chain extenders in solvent-based polyurethanes. For example, they can be used in ink binders, synthetic leather, adhesives and paint applications.
How to use MXDA and 1,3-BAC
(1) Preparation of IPDI prepolymer (60% solids content)
Isocyanate-terminated prepolymers (IPDI prepolymers) consisting of aliphatic isocyanate (IPDI) and polyester polyol (PBA) were synthesized in DMF under the condition that the functional group equivalent ratio NCO/OH = 2.0.
(2) Physical properties when chain-extender is used
Resin properties of samples cured and dried after adding MXDA, 1,3-BAC, and other diamines as chain-extenders to IPDI prepolymer were evaluated; when MXDA was used as a chain-extender, a trend toward higher tensile strength and elongation was observed, indicating that it can improve the strength of polyurethane resin. In addition, the use of 1,3-BAC as a chain-extender produces polyurethanes with better transparency.