Abstract
This study has developed novel fully bio-based resorcinol epoxy resin–diatomite composites by a green two-stage process based on the living character of the cationic polymerization. This process comprises the photoinitiation and subsequently the thermal dark curing, enabling the obtaining of thick and non-transparent epoxy-diatomite composites without any solvent and amine-based hardeners. The effects of the diatomite content and the compacting pressure on microstructural, thermal, mechanical, acoustic properties, as well as the flame behavior of such composites have been thoroughly investigated. Towards the development of sound absorbing and flame-retardant construction materials, a compromise among mechanical, acoustic and flame-retardant properties was considered. Consequently, the composite obtained with 50 wt.% diatomite and 3.9 MPa compacting pressure is considered the optimal composite in the present work. Such composite exhibits the enhanced flexural modulus of 2.9 MPa, a satisfying sound absorption performance at low frequencies with Modified Sound Absorption Average (MSAA) of 0.08 (for a sample thickness of only 5 mm), and an outstanding flame retardancy behavior with the peak of heat release rate (pHRR) of 109 W/g and the total heat release of 5 kJ/g in the pyrolysis combustion flow calorimeter (PCFC) analysis.
Highlights
Diatomite is composed of sediments enriched with silica in the form of siliceous skeletons of diatoms which are a collection of diverse microscopic single-celled algae
The presence of such a resin layer on the one hand makes the obtained material be of sandwich type which is not the objective of the study, on the other hand weakens the sound absorption of the composite
As regards the flame behavior, the flame retardancy feature of the diatomite-based composites is highlighted by their self-extinguishing behavior and by great reductions of their peak of heat release rate (pHRR)
Summary
Diatomite is composed of sediments enriched with silica in the form of siliceous skeletons of diatoms which are a collection of diverse microscopic single-celled algae. The preparation of a bio-sourced epoxy resin from resorcinol diglycidyl ether (RDGE) has been performed using cationic photopolymerization under UV light exposure in our laboratory [24] This process follows the principles of green chemistry due to numerous advantages such as simple equipment, unpolluted formulations, reduced cycle time and absence of solvents as well as harmful amine-based hardeners [25]. The use of such formulations to prepare fully bio-sourced epoxy-diatomite composites seems attractive for developing new functional materials fulfilling environmental criteria. The influences of the compacting pressure and the diatomite content on the microstructural, mechanical, acoustic absorption and flame-retardant properties of epoxy-diatomite composites were thoroughly investigated
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