[en] The polyaddition between dicyclic carbonates and diamines leading to poly(hydroxy urethane)s (PHUs) has emerged as the preferred method for the synthesis of green, non-isocyanate polyurethanes. However, when proposed for use as structural adhesives, the long times for completion of aminolysis of the 5-membered cyclic carbonates under ambient conditions force the use of complementary chemistries to accelerate the curing process. In this work, a system that combines an amino-terminated PHU (NH2-PHU-NH2), an epoxy resin, and a thiol compound was employed to develop high-shear strength PHU-epoxy hybrid adhesives able to cure at room temperature in short times. A NH2-PHU-NH2 prepolymer synthesized by using a sub-stoichiometric quantity of dicyclic carbonates was mixed with a bisphenol A-based epoxy resin for the preparation of the structural adhesive. While this adhesive showed good lap-shear strength and shear resistance under static load and temperature, the curing process was slow. In order to speed up the curing process, a thiol (trimethylolpropane tris(3-mercapto propionate)) was added and its impact on the curing process as well as on the adhesive properties was evaluated. The trifunctional thiol additive allowed for faster curing in the presence of the 1,1,3,3-tetramethylguanidine basic catalyst. Moreover, a combination of NH2-PHU-NH2 and the thiol as curing agents for the epoxy resin resulted in adhesives with superior toughness, without any deterioration of the ultimate lap-shear strength or shear resistance under load and temperature, making these adhesives suitable for high-demand applications in the automotive industry.
Research Center/Unit :
CESAM - Complex and Entangled Systems from Atoms to Materials - ULiège Center for Education and Research on Macromolecules (CERM), Belgium
Disciplines :
Materials science & engineering Chemistry
Author, co-author :
Gomez-Lopez, Alvaro; University of the Basque Country, POLYMAT and Department of Polymers and Advanced Materials: Physics, Chemistry and Technology, Donostia/SanSebastian, Spain
Grignard, Bruno ; University of Liège (ULiège), Complex and Entangled Systems from Atoms to Materials (CESAM) Research Unit, Center for Education and Research on Macromolecules (CERM), Belgium
Detrembleur, Christophe ; University of Liège (ULiège), Complex and Entangled Systems from Atoms to Materials (CESAM) Research Unit, Center for Education and Research on Macromolecules (CERM), Belgium
Sardon, Haritz ; University of the Basque Country, POLYMAT and Department of Polymers and Advanced Materials: Physics, Chemistry and Technology, Donostia/SanSebastian, Spain
Language :
English
Title :
Accelerating the Curing of Hybrid Poly(Hydroxy Urethane)-Epoxy Adhesives by the Thiol-Epoxy Chemistry
F.R.S.-FNRS - Fonds de la Recherche Scientifique EU - European Union
Funding text :
The authors would like to acknowledge the technical and human support provided by SGIker (UPV/EHU and ERDF, EU). A.G.-L. would like to acknowledge the University of the Basque Country for the predoctoral fellowship received to carry out this work and Dr. Nora Aranburu for the help with the lap-shear measurements. ORIBAY Group Automotive also wants to acknowledge HAZITEK program for the financial support of the project n° ZL-2019/00193. The authors want to acknowledge the financial support of the EU through the project NIPU-EJD 9555700. C.D. is FNRS Research Director and would like to thank FNRS for financial support.
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