Abstract
In the presented work the influence of different 3MgO·4SiO2·H2O (talc) contents in polypropylene samples on the structure, hardness, elasticity, and friction of the surface layer was investigated. The talc content ranged from 0 to 25 wt.%, and all the samples were obtained in the same conditions by the injection molding process. The analysis of the microstructure was performed by X-ray diffraction. Changes in the hardness and elasticity were determined for three different depths (300, 800, and 4000 nm) using an ultra nano tester. For the purpose of the examination of the friction properties of the obtained compounds, a nano-scratch tester was applied. Increasing the talc content caused growth in the indentation modulus and hardness values. Simultaneously, an effect of decreasing hardness and elastic modulus with increasing indentation depth was observed. The smallest effect size was observed for 25 wt.% talc content, which might suggest that talc addition increased the homogeneity of the observed composites. Scratch tests showed increasing scratch resistance along with increasing talc content for both constant and progressive loads. The growth in talc concentration led to a decrease in the degree of the polypropylene (PP) crystallinity of the surface layer. The exfoliation process occurred in PP composites.
Highlights
Micromachine parts, such as gears, pulleys, and plain bearings are usually made of polyamide (PA)
The work presented in this paper aimed to investigate changes to the mechanical and structural properties of the surface layers of polypropylene samples filled with different talc contents ranging from 5% to 25%
Our findings have shown that talc, one of the most popular fillers, even in lower concentrations, affected the structural properties of the surface layer of PP-talc composites
Summary
Micromachine parts, such as gears, pulleys, and plain bearings are usually made of polyamide (PA). It is reasonable to look for the components made of materials that are free of this defect and with similar or even better mechanical and sliding properties. In humid environments one of the potential substitutes for polyamide, in a wide range of applications, is polypropylene (PP) [2,3,4,5]. Polypropylene composite is a widely produced and used polymer applied, e.g., in the construction, automotive, packaging, cable-insulation, and household-goods industries [6]. There is a strong need for improvements to PP’s mechanical and thermal properties, mainly by the incorporation of different fillers, especially since polypropylene is characterized by good processability and accepts different types of natural and synthetic fillers [8,9,10,11]. Kaolin, calcium carbonate, and talc are Materials 2020, 13, 698; doi:10.3390/ma13030698 www.mdpi.com/journal/materials
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