New family of functionalized crosslinkers for heat-curable polyurethane systems—A preliminary study

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• 作者：Janusz Kozakiewicz ; ^a ; ^{janusz.kozakiewicz@ichp.pl"" rel=""nofollow} ; Jarosł ; aw Przybylski^a ; Krystyna Sylwestrzak^a ; Izabela Ofat^a
• 关键词：Polyurethane heat-curable systems ; Stoving compounds ; Allophanates ; Blocked polyisocyanates ; Functionalized urethanes ; Polyurethane coatings ; Crosslinkers
• 刊名：Progress in Organic Coatings
• 出版年：2011
• 出版时间：September-October 2011
• 年：2011
• 卷：72
• 期：1-2
• 页码：120-130
• 全文大小：817 K

文摘

In this paper the results of preliminary studies on applying functionalized urethanes as blocking agents for polyisocyanates used commercially in heat-curable polyurethane systems are described. The results of FTIR and GC–MS investigations of the products of NCO-urethane group reaction in a model system consisting of phenyl isocyanate and N-ethylurethane showed that a transurethanization could occur what led to formation of a mixture of allophanates and urethanes of different structures. This was also confirmed by investigating the reaction product of N-ethylurethane and hexamethylenediisocyanate trimer (HDIT). The studies of thermal decomposition of model functional allophanates and functional urethanes by TGA–FTIR showed that not only allophanate group, but also urethane group dissociated around 170 °C releasing free NCO groups. Taking into account findings of investigations carried out with model systems certain new functionalized allophanate compounds of structure (I) were obtained in the reaction of HDIT and urethanes substituted with alkoxysilane and/or unsaturated bond. Determination of changes in rheological properties of compositions of such functionalized allophanates with polyols during heating at 150 °C showed that the gelling took place in a relatively short time what confirmed that the desired curing proceeded. It was also proved that when unsaturated bond was present in the functionalized allophanate structure gelling time was shorter what suggested that poolymerization occurred along with NCO–OH reaction. The properties of coatings obtained from simple coating formulations containing allophanate functionalized with double bonds and alkoxysilane groups applied as crosslinker (gloss, hardness, elasticity, adhesion, cupping ability) were comparable to the properties of similar coatings obtained from a simple standard system composed of the same polyol and a commercial blocked polyisocyanate.