The increased compression strength of an epoxy resin with the addition of heat-treated natural nano-structured diatom frustules

Abstract

Natural diatom frustules composing nanometer size silica particles were heat-treated at temperatures between 600 and 1200℃ for 2 h and used as filler/reinforcing agent (15 wt%) in an epoxy resin. The opal structure of as-received natural diatom frustules was transformed into cristobalite after the heat-treatment above 900℃. The epoxy resin test samples reinforced with heat-treated and as-received frustules and neat epoxy test samples were compression tested at the quasi-static strain rate of 7 × 10−3 s−1. The results showed that the inclusion of the frustules heat-treated at 1000℃ increased the compressive yield strength of the resin by 50%, while the addition of the diatom frustules heat-treated above and below 1000℃ and the as-received frustules increased the strength by ∼25% and 16%, respectively. The heat treatment above 1000℃ decreased the surface area of the frustules from 8.23 m2 g−1 to 3.46 m2 g−1. The cristobalite grains of the frustules heat-treated at 1000℃ was smaller than 100 nm, while the grain size increased to ∼500 nm at 1200℃. The increased compressive stresses of the resin at the specific heat treatment temperature (1000℃) were ascribed to nano size crystalline cristobalite grains. The relatively lower compressive stresses of the epoxy resin filled with frustules heat-treated above 1000℃ were attributed to the micro-cracking of the frustules that might be resulted from higher density of the cristobalite than that of the opal and accompanying reduction of the surface area and the surface pore sizes that might impair the resin-frustule interlocking and intrusion.

The Shape and Size Effect of the Diatom Frustule Addition on the Compression Behavior of an Epoxy

“…In a previous study, the compressive modulus and yield strength of an epoxy matrix were shown to increase with the diatom frustule addition and the stress enhancement of filled epoxy was ascribed to relatively high strength of frustules and strong interlocking between the frustules and the polymer matrix [5,14]. It was also shown that the filling the epoxy matrix with the heat-treated frustules at a certain temperature maximized the matrix strengthening of the composite [15]. The present study is a continuation of the previous studies and aims to investigate the effect of diatom frustules' shape and size on the compression stress-strain behavior of a polymer matrix at quasi-static strain rate.…”

Dual UV-Thermal Curing of Biobased Resorcinol Epoxy Resin-Diatomite Composites with Improved Acoustic Performance and Attractive Flame Retardancy Behavior

“…The development of composites using diatomite as siliceous fillers is an alternative to the sintering technique for advanced diatomite-based material prospects. Examples of composites using diatomite in various types of polymeric matrices such as epoxy [9], polyacrylate [10], polyetherimide [11], polyurethane [12], polylactide [13], chitosan [14], or different kinds of rubber [15] have shown the improvement of thermal stability and mechanical properties of composites. In these researches, the fillers have been incorporated at a rate not exceeding 15% by weight for the mechanical reinforcement purpose.…”

Diatomite‐filled epoxy resin composites: Curing behavior, dielectric, and thermal properties

“…To reduce the proportion of the petroleum-based polymers in engineering materials, the research, and application of bio-composites can solve this problem, while allowing the use of natural raw materials. [1][2][3][4][5][6] As an essential industrial raw material, epoxy resins are widely used as matrices in many applications such as coatings, adhesives, electronic materials, and printed circuit boards due to their low shrinkage, good chemical resistance, hydrophobicity, electrical insulation, and other outstanding properties. [7][8][9][10][11][12][13][14] However, the brittleness and high dielectric constant limit the application of epoxy resins in the fields of integrated circuits and semiconductors.…”