Methodological Aspects of Obtaining and Characterizing Composites Based on Biogenic Diatomaceous Silica and Epoxy Resins

Abstract

Diatomaceous earth are sediments of unicellular algal skeletons with a well-defined hierarchical structure. Despite many tests conducted on systems using diatomaceous earth and epoxy resins, we can find many differences in the methods of acquisition and characteristics of the composite, which may considerably affect the results. In our study, we have conducted tests to verify the impact of the method of obtaining samples and the degassing of the composite on its mechanical properties and standard deviation. The samples were cast in glass moulds and silicone moulds and then subjected to testing for their mechanical and functional properties, imaging with the use of an optical microscope and a scanning electron microscope. The tests have shown that, for samples cast in glass moulds, there is no heterogeneity within the area of the tested sample, as in the case of samples cast in silicone moulds. Silicone moulds allow for quite effective self-degassing of the resin due to the large area-to-mass ratio, and the small remaining air vesicles have a limited effect on the mechanical properties of the samples. The filler used also played a significant role. For systems containing base and rinsed diatomite, it is clear that the degassing of mixtures increases the tensile strength. For treated diatomite, the elongation at break grew along with increasing filler concentration, while for base diatomite, the improvement was observed for flexural strength and impact strength. A non-modified epoxy resin shows a tensile strength at 19.91 MPa (silicone mould cast). At the same time, the degassed, glass mould-cast systems containing 12% of base and rinsed diatoms showed a tensile strength of 27.4 MPa and 44.7 MPa, respectively. We have also observed that the higher the filler concentration, the higher were the tensile strength values, which for the rinsed diatoms reached over 55.1 MPa and for the base diatoms were maximum of 43.8 MPa. The tests, therefore, constitute a set of guidelines and recommendations for testing with the use of fillers showing an extended inner structure.

Where ppm Quantities of Silsesquioxanes Make a Difference—Silanes and Cage Siloxanes as TiO2 Dispersants and Stabilizers for Pigmented Epoxy Resins

“…Although the studied materials share the same polymer matrix and the base pigmenting filler, the preparation methodology applied and the coupling agent used cause subtle structural and interfacial differences that can be elucidated with DSC (Figure 17, top). Epoxy systems of similar polymer matrix were studied earlier [40,42]. It can be seen that for the second heating cycle, the T g of most of the samples appears at ~120 • C, being close to that of the neat epoxy (Figure 17, bottom).…”

Biocomposites Based on Polyamide 11/Diatoms with Different Sized Frustules

“…The original diatomaceous earth was fractionated in a similar way as in the previous works [ 36 , 37 , 38 , 39 ], according to Figure 4 . Amorphous diatomite weighing 15 kg was placed in barrel 1, which was filled to a volume of 140 L with demineralized water.…”

“…Diatomite is considered biofriendly, non-toxic, and used for multiple applications, including as an adsorbent and filtering medium in wastewater treatment and other purification procedures, cement production and as a polymer filler [ 35 ]. In our previous works, we tested diatomaceous earth as a filler in different polymer systems, including epoxy composites [ 36 , 37 ], injection-molded PLA [ 38 ] and PLA-based composite filaments for FDM 3D printing [ 39 ].…”

Influence of Diatomaceous Earth Particle Size on Mechanical Properties of PLA/Diatomaceous Earth Composites

“…In previous papers [ 23 , 24 ], we focused on the creation of epoxy resin/diatomaceous earth composites, which allowed for an observation of the effects of the modifier on changes in the parameters of the uncured epoxy resin. Moreover, we investigated the effects of diatomaceous earth on the process of manufacturing composites and related difficulties.…”