TY - BOOK

T1 - Self-Healing Approaches for Melamine-Based Surfaces

AU - Urdl, Katharina

N1 - embargoed until 22-05-2024

PY - 2019

Y1 - 2019

N2 - In this thesis, a self-healing effect of melamine-based surfaces, triggered by temperature, was investigated. The temperature triggered reversible healing chemistry, on which the self-healing effect was based, was the Diels-Alder reaction between furan and maleimide groups. Melamine-furan containing particles or building blocks were coupled by a multi-functional ma-leimide crosslinker via a Diels- Alder (DA) reaction and a coating film was formed. In the first part of the thesis, furan functionalised thermosetting melamine particles were ob-tained by using a co-polymerisation technique of melamine-formaldehyde and furan-formaldehyde resin. The particles had a significant amount of furan groups present at their surface, however, the approach to start with two different kinds of pre-polymers lead to unsat-isfactory chemical homogeneity of the obtained particles: the particles consisted of fairly large distinct regions consisting of either only (DA unreactive) melamine formaldehyde or (DA re-active) furan formaldehyde substructures. Since only furan rich regions were able to undergo thermoreversible DA reactions, the potential of self-healing effects could not be exploited ho-mogeneously over the particle surface to the highest possible extent. The density of DA reac-tive groups on the particle surface seemed to be too low. In the second part of the thesis, a different concept was established. To increase the density of reactive groups on the particle surface and improve reactivity towards maleimides, a dif-ferent approach was pursued: instead of using pre-polymers, a novel bi-functional monomer was synthesised which carried both, the network building melamine and the DA reactive furan moieties in one molecule. By using the bi-functional monomer in the particle production, a more homogenous distribution and higher density of DA reactive groups on the surface of the particles produced was obtained. These particles displayed improved reactivity towards ma-leimide groups. In the third part of the thesis, the DA reaction of the novel furan-melamine (Fu-Mel) monomer bi- and multi-functional maleimide crosslinker was studied. The most favourable reaction conditions to perform an efficient DA and retro DA (rDA) reaction in the coating systems was evaluated. The explored reaction conditions were directly transferred to particle-crosslinker networks in order to obtain reversibly crosslinkable coating systems. In the last part of the work, a DA resin was established. Firstly, the DA adduct was formed between a Fu-Mel and a BMI. The DA adduct was then reacted with formaldehyde to form a network by conventional condensation reaction of melamine amino groups with formalde-hyde. The obtained resin was used for the impregnation of paper or was directly used for the characterisation. Impregnated papers and neat resin were used to perform scratch-healing tests and mechanical analysis of the new coating system.

AB - In this thesis, a self-healing effect of melamine-based surfaces, triggered by temperature, was investigated. The temperature triggered reversible healing chemistry, on which the self-healing effect was based, was the Diels-Alder reaction between furan and maleimide groups. Melamine-furan containing particles or building blocks were coupled by a multi-functional ma-leimide crosslinker via a Diels- Alder (DA) reaction and a coating film was formed. In the first part of the thesis, furan functionalised thermosetting melamine particles were ob-tained by using a co-polymerisation technique of melamine-formaldehyde and furan-formaldehyde resin. The particles had a significant amount of furan groups present at their surface, however, the approach to start with two different kinds of pre-polymers lead to unsat-isfactory chemical homogeneity of the obtained particles: the particles consisted of fairly large distinct regions consisting of either only (DA unreactive) melamine formaldehyde or (DA re-active) furan formaldehyde substructures. Since only furan rich regions were able to undergo thermoreversible DA reactions, the potential of self-healing effects could not be exploited ho-mogeneously over the particle surface to the highest possible extent. The density of DA reac-tive groups on the particle surface seemed to be too low. In the second part of the thesis, a different concept was established. To increase the density of reactive groups on the particle surface and improve reactivity towards maleimides, a dif-ferent approach was pursued: instead of using pre-polymers, a novel bi-functional monomer was synthesised which carried both, the network building melamine and the DA reactive furan moieties in one molecule. By using the bi-functional monomer in the particle production, a more homogenous distribution and higher density of DA reactive groups on the surface of the particles produced was obtained. These particles displayed improved reactivity towards ma-leimide groups. In the third part of the thesis, the DA reaction of the novel furan-melamine (Fu-Mel) monomer bi- and multi-functional maleimide crosslinker was studied. The most favourable reaction conditions to perform an efficient DA and retro DA (rDA) reaction in the coating systems was evaluated. The explored reaction conditions were directly transferred to particle-crosslinker networks in order to obtain reversibly crosslinkable coating systems. In the last part of the work, a DA resin was established. Firstly, the DA adduct was formed between a Fu-Mel and a BMI. The DA adduct was then reacted with formaldehyde to form a network by conventional condensation reaction of melamine amino groups with formalde-hyde. The obtained resin was used for the impregnation of paper or was directly used for the characterisation. Impregnated papers and neat resin were used to perform scratch-healing tests and mechanical analysis of the new coating system.

KW - Melamin

KW - Formaldehyd

KW - furan-funktionalisiert

KW - Partikel

KW - Diels-Alder

KW - Self-Healing

KW - reversible Reaktionen

KW - melamine

KW - formaldehyde

KW - furan functionalised

KW - particles

KW - Diels-Alder

KW - self-healing

KW - reversible reaction

M3 - Doctoral Thesis

ER -