Abstract
This paper presents the impact of accelerated aging on selected mechanical and thermal properties of isotactic polypropylene (iPP) composites filled with sedimentary hybrid natural filler-Opoka rock. The filler was used in two forms: an industrial raw material originating as a subsieve fraction natural material, and a rock calcinated at 1000 °C for production of phosphorous sorbents. Fillers were incorporated with constant amount of 5 wt % of the resulting composite, and the material was subjected to accelerated weathering tests with different exposition times. The neat polypropylene and composites with calcium carbonate as a reference filler material were used for comparison. The aim of the research was to determine the possibility of using the Opoka rock as a new hybrid filler for polypropylene, which could be an alternative to the widely used calcium carbonate and silica. The thermal, mechanical, and structural properties were evaluated by means of differential scanning calorimetry (DSC), tensile tests, scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy with attenuated total reflectance (FTIR/ATR) prior to and after accelerated aging. As a result, it was found that the composites of polypropylene with Opoka were characterized by similar or higher functional properties and higher resistance to photodegradation compared to composites with conventional calcium carbonate. The results of measurements of mechanical properties, structural and surface changes, and the carbonyl index as a function of accelerated aging proved that Opoka was an effective ultraviolet (UV) stabilizer, significantly exceeding the reference calcium carbonate in this respect. The new hybrid filler of natural origin in the form of Opoka can therefore be used not only as a typical powder filler, but above all as a UV blocker/stabilizer, thus extending the life of polypropylene composites, especially for outdoor applications.
Highlights
With the development of industrial technologies, the demand for polymer materials continues to increase
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
The fillers used in the tests were: calcium carbonate (CaCO3) 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 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
Summary
With the development of industrial technologies, the demand for polymer materials continues to increase. Increasing pollution of the natural environment and depletion of global oil and coal deposits force the industry to search for and develop new, more sustainable, and low-energy polymer materials [2,3,4]. Oxygen affects polymers already during their conversion into specific goods during polymer processing, as well as during their use; ozone is highly corrosive to all organic materials when applied as a sterilizing agent or existing as tropospheric ozone. This action of different forms of oxygen, along with other atmospheric factors, promotes the formation of free radicals, which through the degradation process, cause changes in the molecular and macromolecular structure, and cross-linking of polymers [20]. The degradation causes the deterioration of the chemical, physical, and mechanical properties of polymeric materials, and significantly shortens their service life [21,22]
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