Abstract
The pure trifunctional glycidyl monomer from phloroglucinol (3EPO-Ph) was synthesized and used as feedstock in the preparation of novel bio-based thermosets by thiol-epoxy curing. The monomer was crosslinked with different commercially available thiols: tetrafunctional thiol (PETMP), trifunctional thiol (TTMP) and an aromatic dithiol (TBBT) as curing agents in the presence of a base. As catalyst, two different commercial catalysts: LC-80 and 4-(N,N-dimethylamino) pyridine (DMAP) and a synthetic catalyst, imidazolium tetraphenylborate (base generator, BG) were employed. The curing of the reactive mixtures was studied by using DSC and the obtained materials by means of differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and dynamic mechanical thermal analysis (DMTA). The results revealed that only the formulations catalyzed by BG showed a latent character. Already prepared thermosetting materials showed excellent thermal, thermomechanical and mechanical properties, with a high transparency. In addition to that, when compared with the diglycidyl ether of bisphenol A (DGEBA)/PETMP material, the thermosets prepared from the triglycidyl derivative of phloroglucinol have better final characteristics and therefore this derivative can be considered as a partial or total renewable substitute of DGEBA in technological applications.
Highlights
Nowadays, polymeric eco-friendly materials have been extensively studied as substitutes of commercial materials derived from oil to be used in future industrial applications
They have been used as partial or total substitutes of oil-derived epoxy resins such as diglycidyl ether of bisphenol A (DGEBA), which is classified as unsafe because it can act as an endocrine disruptor and is not suitable for applications related to the food industry
The present study proposes the preparation of a pure triglycidyl monomer which has a high functionality and a compact structure (3EPO-Ph) that willphloroglucinol be later cured by a thiol-epoxy has a high functionality and a compact structure (3EPO-Ph) that will be later cured by a thiol-epoxy click reaction in the presence of a base
Summary
Polymeric eco-friendly materials have been extensively studied as substitutes of commercial materials derived from oil to be used in future industrial applications. In a previous study of our group, two new epoxy monomers based on eugenol were synthetized phenolic compounds are a good renewable alternative to commercial oil-derived resins [16,17]. The final materials showed excellent thermal and mechanical all the epoxy groups of 3EPO-Ph resin were transformed into phosphate groups and this new characteristics and the addition of the triphosphate improved considerably the flame retardancy of the compound was used as additive for commercial epoxy resins. The use of several amines as basic catalyst, such as N-benzyldimethylamine, in thiol-epoxy formulations, leads to an excessive fast reaction that makes difficult to industrially apply these formulations For this reason, the use of several tertiary amines which showed a certain latent character (LC80 and DMAP), has been essayed together with a thermally activated base generator catalyst. This base generator synthesized by us can be photochemically and thermally activated as it was previously demonstrated [27]
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