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Welcome to ResearchSpace, the institutional repository of the CSIR. ResearchSpace is an open access electronic archive collecting, preserving and distributing scholarly digital materials created by the CSIR.

Recent Submissions

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Polyaniline as a dual flame retardant and electrostatic dissipative additive in polyethylene nanocomposites

(2024-10) Adisa, A; Asante, JKO; Ojijo, Vincent O; Mapossa, AB; Mhike, W

Polyolefins, such as polyethylene (PE), are highly flammable and electrically insulative, limiting their applicability. The study explored the flame-retardancy and electrical conductivity of PE/polyaniline (PE/PANI) nanocomposites containing undoped PANI, PANI doped, and co-doped with various acids and PANI modified with a double layered hydroxide or ammonium polyphosphate (APP). The nanocomposites were synthesized through in situ chemical oxidative polymerization of aniline and compression molding. Flame retardancy was evaluated using UL 94 tests and cone calorimetry. All nanocomposites, except the de-doped PANI nanocomposite, attained a UL 94 V2 rating. Cone calorimeter results showed that PANI doped with H3PO4 reduced the peak heat release rate by 20% compared to neat PE, whereas co-doping PANI with H3PO4 and phytic acid reduced it by 31%. The nanocomposites exhibited volume resistivity for suitable for electrotactic dissipation applications but showed marginally reduced mechanical properties. This study demonstrates the potential to develop electrostatic dissipative and flame-retardant PE nanocomposites incorporating PANI.

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Analysis of failure characteristics of screen plates of ring hammer crusher used in coal handling applications

(2024-08) Kyekyere, E; Olakanmi, EO; Prasad, RVS; Matshediso, B; Motimedi, T; Botes, A; Pityana, Sisa L

The screen plate, a critical component within a ring hammer crusher (also known as a ring granulator or rolling ring crusher), plays a vital role in the secondary crushing of coal. Functioning both as a platform for coal crushing and as a sieve to achieve the desired coal size, it is essential to understand and examine its failure characteristics to enhance its mechanical and wear resistance properties in coal handling applications. This study thoroughly explored the failure modes, mechanisms, and underlying causes of screen plate failures. Microscopic techniques such as optical microscopy (OM), scanning electron microscopy (SEM), Vickers microhardness test and spectrochemical analysis were utilised to identify the failure mechanism. Failure modes identified from the macroscopic analysis were discharged hole widening, hole wall break-off, plate edge crack, plate fracture, one-sided edge slimming, and general surface wear of the screen plate. The fractographic and wear track analysis identified the principal failure mechanisms of three-body abrasive wear, two-body sliding abrasion wear, shear-induced fatigue fracture and brittle shear fracture. The root causes of the failures are the rotor’s direct impact, defects in the parent material, the presence of hard materials in the coal and the use of unsuitable steel grade in the screen plate manufacturing. The service life of the screen plate can be improved through proper material selection, uniform crusher feeding, surface modification of the surface of the “as purchase” screen plate with appropriate wear-resistant materials, and adherence to good maintenance practices.

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Cost effective ballistic protection for vehicles

(2024-01) Jones, JD; Reinecke, John D; Pambuka, L

In the design of protected vehicles there is a constant trade-off between mobility, protection, and cost. To protect against increasing threat levels, designers are usually required to use armour materials with increased mass and thickness. However, this has a negative effect on the vehicle’s mobility. Reducing the mass of armour plates for the same level of protection usually requires the use of more expensive materials, thus increasing the cost. The aim of this project was to investigate how the areal density of armour plates, used for vehicle protection against a NATO Level 3 ballistic threat, can be reduced whilst still maintaining the required level of threat protection, and optimising cost by exploring varying material layers in a composite armour plate assembly. This work used computational modelling to evaluate protection capabilities of various combinations of lower cost materials that were then manufactured and tested. The test plate combination initially selected were based on the published computational work of Rahman et al., [2]. These proposed, multilayered, plates computationally provided a reduction in aerial density of 12% compared to equivalent homogeneous amour steel plate. Additional plate combinations, using Strenx 700E Al-7075-T6 with Kevlar and Dyneema layers, were proposed and computationally evaluated and assessed. These multilayered plates were then manufactured and subjected to ballistic tests against NATO level 3 (7.62 x 51 mm Tungsten Carbide (WC)) armour piecing rounds. None of the proposed and computationally verified plates provided the required ballistic protection. The main reason for this is ascribed to the application and use of only published material parameters and the implementation of the failure model.

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A summary of green hydrogen as an upcoming energy storage technology

(2024-10) Karamanski, Stefan; Grobler, Jan H; Hlalele, Thabo G

The increasing renewable energy production trend poses concerns about energy dispatchability. The intermittency of renewable energy requires compensating reliable and suitable energy storage technologies. An upcoming energy storage technology is green hydrogen. Green hydrogen has received both extremes of praise and criticism from the energy industry. This study aims to dispel misconceptions about green hydrogen. Green hydrogen and its applications are thoroughly yet concisely described, together with its suitability in power systems. The advantages and disadvantages of green hydrogen are discussed. It was found that green hydrogen has significant benefits of longterm energy storage and strong suitability in heavy industries. Despite green hydrogen decreasing in cost, it is still comparatively expensive and suffers from significant logistical constraints. Green hydrogen remains an important factor in the renewable energy transition and forms an integral component of the energy storage of the future. This study is useful for policy makers, system operators, renewable energy developers and financial institutions that would like an improved understanding of green hydrogen and its integration.

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Investigating top-down cracking of pavement in recycled waste plastic asphalt

(2024-10) Abejide, Samuel O; Adedeji, J; Mostafa, MH

This study investigates a new approach for the use of an alternative sustainable wearing course material on flexible pavement roads (recycled asphalt plastic pavement). Highway infrastructure plays a major key role in the domestic transportation of people, goods and services within the community and from a national perspective. Thus, highway infrastructure provides provincial and local accessibility, which promotes the growth and development of the economy. For this reason, there is a need to develop a sustainable approach to increase the efficiency of transportation infrastructure. The purpose of this study was to evaluate top-down fatigue cracking failure mode of asphaltic wearing courses for use in in pavement overlays, at high traffic intersection points and on parking sections using dual tire loads in finite element analysis. The process of developing alternative mixing materials is initiated by the need to provide a stable mixture for use on field sections different from cold mix or conventional hot mix (HMA) materials, which is subjected to stripping delamination mode with increasing moisture content. In this study, it was observed that the bonds formed between the molten plastic material has the potential to bind the bitumen and the aggregates together as a homogenous material in such a way that, when hardened at reduced temperatures, the mix is able to form a stronger bonded material that is semipervious and allows drainage of moisture or water across the surface of the asphalt plastic layer. This study adopts an alternative approach to the design of an ultrathin film asphalt concrete porous pavement layer for use in pavement surface wearing course and high-density traffic roads considering the effects of increasing temperature and moisture absorption on the asphalt plastic pavement mix .