Opoka—Sediment Rock as New Type of Hybrid Mineral Filler for Polymer Composites

Abstract

The work presents a comprehensive profile of the physicochemical characteristics of opoka sedimentary rock in the context of its use as a hybrid filler for thermoplastics. Determining the functional parameters of the studied filler was the main aim of this research. Thermal treatment leads to changes in its morphology and phase composition. A wide range of physicochemical techniques was used, such as low-temperature nitrogen adsorption, FT-IR, TGA, XRD, optical, and electron microscopy. The susceptibility of the material to micronisation was also tested (ball milling). Due to its widespread occurrence, opoka can be an attractive alternative to fillers such as silica or chalk. In order to verify this statement, polypropylene composites thereof were prepared by melt blending and injection molding, and studied by mechanical testing and microscopic imaging.

The Accelerated Aging Impact on Mechanical and Thermal Properties of Polypropylene Composites with Sedimentary Rock Opoka-Hybrid Natural Filler

“…The fillers used in the tests were: calcium carbonate (CaCO 3 ) Omyacarb 2-VA (Omya, Warsaw, Poland), with an average grain size (d50) of 3.86 µm, and two types of Opoka: first in the form of industrial raw material originating (as a subsieve fraction) from the production of sorbents used in water-treatment processes; and second in the form of waste rock calcinated at 1000 °C for production of ceramics. The raw Opoka consisted of CaCO 3 /SiO 2 , and the calcinated Opoka of CaO/SiO 2 [ 43 ]. The samples were named in reference to the filler type.…”

“…The average grain size (d50) of the Opoka samples was 28.6 µm and 29.4 µm, respectively. Detailed description of physicochemical properties of the filler was presented in our previous work [ 43 ].…”

“…Opoka is a mineral material of natural origin with potential use as a novel hybrid filler for polymers. Opoka is a sedimentary rock, being a transitional form between carbonate and siliceous rocks, formed in the Upper Cretaceous period as a result of the decalcification of primary rocks [ 42 ], and was extensively characterized in our previous work [ 43 ]. The content of silica (SiO 2 ) in Opoka rock ranges from 5 to 75 wt %, and it occurs predominantly in the form of opal, chalcedony, or quartz.…”

“…Owing to their thermal and mechanical properties, Opoka finds application in the building industry, cement production, road construction, and the manufacture of decorative lining and ceramic materials [ 42 , 46 ]. The sorption properties of Opoka materials are utilized in the processes of water and sewage purification to remove phosphorus, magnesium, and iron, among others [ 43 , 47 ].…”

“…Due to the content of both calcium carbonate and silica in the chemical composition of Opoka, as well as its interesting physicochemical properties [ 43 , 48 ], the aim of this study was to determine the influence of accelerated aging on the thermal and mechanical properties of polypropylene composites filled with Opoka as a hybrid natural filler. This was a continuation of our study on Opoka/iPP composites, in which the mechanical properties of the obtained composites and the processability (compounding and dispersion) of the filler were covered previously.…”