Repositori URV

Identificador: TDX:807

Handle: https://hdl.handle.net/20.500.11797/TDX807

Autors:
González Búrdalo, Lidia

Resum:
Thermosetting polymers are interesting materials widely versatilities in the electronics industry because of their good characteristics. The present work is included in this field and it is focused in obtaining new epoxydic thermosets that may be useful as coatings for electronic devices. The objectives posed in this work were to obtain materials that: 1) undergo low shrinkage during curing process, 2) allow to be thermally degraded in a controlled way once their service life is over and 3) improve the mechanical properties with respect to the conventional epoxy materials. The shrinkage of the polymeric network during curing process produces internal mechanical stress and consequently it can lead to the appearance of microvoids and microcracks. Spiroorthoesters (SOEs) are considered to be expandable monomers, which experience expansion during polymerization process. SOEs can be synthesized by reaction of epoxides with lactones in the presence of a Lewis acid as catalyst. The expansion in volume of these monomers is due to the ring-opening polymerization process. It produces a change in atomic distances from the cyclic form (covalent distance) to the open one (Van der Waals distance). The copolymerization of epoxy resins with lactones in the presence of a Lewis acid leads to 'in situ' formation of spiroorthoesters. Once it is formed, it polymerizes yielding poly(ether-ester) unities into the three-dimensional network. On polymerizing expansion is produced, just when the material has no mobility and therefore avoiding internal stress. The typical structure of a thermoset implies that once it is applied over an electronic device neither solvents nor heat can remove it. The introduction of ester groups into the network, especially if are tertiary, allows diminishing the te