Abstract
In this work, two urethane diols with different middle chain lengths were prepared by the non-isocyanate approach from 1,4-diaminobutane or 1,6-diaminohexane with ethylene cyclic carbonate at room temperature without the aid of a catalyst. Different weight percentages of hexa(methoxymethyl) melamine (HMMM) crosslinker was mixed with urethane diols then cured under elevated temperature to generate the melamine-formaldehyde (MF) coating films. Two different linear diols without urethane linkage were chosen to crosslink with HMMM as the control group. The mechanical properties of these MF coatings were investigated by tensile test, adhesion test, and conical mandrel bend test. It was found that coatings incorporated with urethane diols exhibited enhanced mechanical properties and flexibility. These properties were also influenced by the weight percentage of HMMM crosslinker. This study provided a facile non-isocyanate way to produce urethane diols and successfully applied them in MF coating.
Highlights
Thiswere method has caught more attention due to the straighttwoand urethane obtained by a non-isocyanate process from cyclic forward synthesis procedure and the formation of secondary hydroxyl groups from the carbonate and linear diamines with different chain lengths, they were crosslinked ring-opening of cyclic carbonate which can be further functionalized or react with other with hexa(methoxymethyl) melamine (HMMM) to get the coatings with different flexibilities and mechanical properties
Urethane diols were dissolved into ethanol and mixed well with the crossThe MF coatings were generated from urethane diols and the HMMM crosslinker
Characterization results showed that diols with urethane groups in MF coatings can bring better mechanical properties compared to those from the linear diols
Summary
Some alternative and green methods have been explored to obtain urethane linkages, such as the reaction of cyclic carbonate and amines This method has caught more attention due to the straightThe traditional pathway to synthesize urethane groups induces environmental conforward synthesis procedure and the formation of secondary hydroxyl groups from the cerns and safety issues. Thiswere method has caught more attention due to the straighttwoand urethane obtained by a non-isocyanate process from cyclic forward synthesis procedure and the formation of secondary hydroxyl groups from the carbonate and linear diamines with different chain lengths, they were crosslinked ring-opening of cyclic carbonate which can be further functionalized or react with other with HMMM to get the coatings with different flexibilities and mechanical properties. Dodecanediol, ethanol, and methylene chloride were purchased from Sigma-Aldrich
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