ResearchSpace :: Browsing by Author "John, Maya J"

Browsing by Author "John, Maya J"

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Advanced materials for application in the aerospace and automotive industries
(CSIR, 2008-11) Damm, O; Du Preez, W; Trollip, N; John, Maya J
The CSIR conducts research and development (R&D) involving advanced materials with applications in the local automotive and aerospace industries. The relevance of these R&D programmes is illustrated by positioning them in the context of key industry trends and drivers and South Africa’s ability to respond to these. Examples of CSIR R&D on light metals and advanced composite materials, including the successes achieved in mobilising complementary expertise at universities in support of these projects, are given. Finally, the progress made and the impact already achieved or expected in future, are described
Advanced of Starch-Based Bioplastics
(Elsevier, 2024) Mtibe, Asanda; Nomadolo, Elizabeth N; Hlekelele, Lerato; Mokhena, TC; Ofosu, Osei; John, Maya J; Ojijo, Vincent O
The potential of starch-based plastics is well-known and well-researched. In recent years, starch-based materials have been used in both commercial and industrial applications to develop biodegradable and sustainable products and address the negative impacts caused by synthetic plastic products. Synthetic plastics are derived from petroleum-based resources and are non-biodegradable, causing plastic waste pollution. Starch-based bioplastics are selected as an alternative to synthetic plastics due to their availability, renewability, sustainability, biocompatibility, and biodegradability. The conversion of starch into thermoplastic starch (TPS) will be discussed in this study. In addition, the development of starch-based bioplastics using different processing techniques such as melt extrusion, injection molding, compression molding, blown film extruder as well as 3D and 4Dprinting will be also discussed. The market analysis of starch and starch-based materials, their properties, and applications, as well as prospects to determine if starch-based bioplastics are economically and practically feasible, will be thoroughly discussed.
Agave nonwovens in polypropylene composites: mechanical and thermal studies
(SAGE Publications, 2015-03) John, Maya J; Sikampula, N; Boguslavsky, L
Blends of agave fibres with wool waste, pineapple leaf fibres and polypropylene fibres were manufactured by needle-punching technique. Composites were prepared with polypropylene matrix by the process of compression moulding. The effects of blend nonwovens on the mechanical and dynamic mechanical properties of composites were investigated. Composites containing agave-polypropylene (A-PP) nonwovens exhibited superior mechanical properties compared to the other two. Storage modulus of the composites was found to be maximum for agave-pineapple (A-PALF) composites due to the increased stiffness of the composites. Damping was found to be decreased with incorporation of agave nonwovens. As part of product development, parcel trays for automotives were developed from A-PP nonwovens by compression moulding technique. This study looks at the effective utilization of plant and animal fibre waste in composites.
Antibiotic 3D printed Materials for healthcare applications
(Elsevier Inc, 2020-05) Mokhena, Teboho C; John, Maya J; Mochane, MJ; Sadiku, ER; Motsoeneng, TS; Mtibe, Asanda; Tsipa, PC; Kokkarachedu, V; Kanikireddy, V; Sadiku, R
Since its introduction in the past 25 years, three-dimensional (3D) printing has been a major research topic owing to its potential to overcome the limitations of conventional 3D manufacturing techniques, that is, to control the overall architecture toward various applications. In the third (2013–present) decade, 3D printing enters a new phase in which researchers fabricate clinical constructs that benefit the current society. In this chapter, we briefly discuss the recent progress of 3D printing and challenges related to the antibiotic materials and manufacturing process for biomedical applications.
Application of electrospun materials in oil–water separations
(Scrivener Publishing LLC, 2020-04) Mokhena, Teboho C; John, Maya J; Mochane, MJ; Tsipa, PC; Boddula, RI; Ahamed, MI; Asiri, AM
There has been ever-increasing pressure to come up with novel strategies for oily wastewater treatment since it affect the available water sources, crop production, aquatic life and human health. Electrospun nanofibrous materials with attractive attributes, such as interconnected porous structure, large surface-to-area ratio, malleable mechanical properties, tuneable wettability, and porosity have a huge potential for oily wastewater treatment. In this chapter, the recent progress of oil/ water separation using electrospun nanofibrous materials is reviewed. The challenges and future prospects of this new field are also described.
Bio-based coatings for reducing water sorption in natural fibre reinforced composites
(Macmillan Publishers Limited, 2017-10) Mokhothu, Thabang H; John, Maya J
In this study, bio-based coatings were used for reducing water sorption of composites containing flame retardant treated natural fibres and phenolic resin. Two types of coatings; polyfurfuryl alcohol resin (PFA) and polyurethane (PU) were used on the composites and compared with a water resistant market product. Uncoated and coated samples were conditioned at 90 °C and relative humidity of 90% for three days and the relative moisture content and mechanical properties after conditioning were analysed. In addition, the changes in the weight loss of the conditioned samples were also investigated by thermogravimetric analysis. The moisture diffusion characteristics of coated laminates were also studied at room temperature under water immersion conditions. PFA coated samples showed better moisture resistance and mechanical performance than other bio-based coatings when subjected to long term environmental aging.
Bio-based fillers for environmentally friendly composites
(Wiley. Scrivener Publishing., 2017-03) Mokhothu, Thabang H; John, Maya J
The use of bio-based fillers as alternative replacement for synthetic fillers has been dictated by increasing ecological concerns as well as depleting petroleum resources. The other aspect is a growing need for eco-friendly, renewable and sustainable products. In recent years, natural fibers have gained attention as suitable reinforcements in polymeric matrices because they are biodegradable, low cost, environmentally friendly and renewable. Furthermore, they possess high specific strength and can be effectively used for composites in various applications. This chapter will give an overview of the different types of bio-based fillers (natural fibers, lignin, cellulose and rice husk) used in biopolymer matrices. The application of these green composites in the industrial area will also be discussed.
Bio-based structural composite materials for aerospace applications
(South African International Aerospace Symposium, 2008-09) John, Maya J; Anandjiwala, RD; Wambua, P; Chapple, Stephen A; Klems, T; Doecker, M; Goulain, M; Erasmus, Louwrence D
Currently, one of the research programs at CSIR is focused on developing composites from natural fibre and phenolic matrices to be used as side panels in aircraft structures. Efforts are underway to solve the issues related to strength, adhesion between fibre and matrix, moisture and thermal durability besides compliance to meet with airworthiness standards. The latter part of the program will deal with biopolymer matrices which would lead to development of green composites for aerospace applications. The present paper will discuss approaches and methodology used and some preliminary results highlighting the challenges involved
Biodegradability of biobased polymeric materials in natural environments: Structures and Chemistry
(Scrivener Publishing LLC, 2017-03) Muniyasamy, Sudhakar; John, Maya J
The development of biobased polymer materials from renewable resources meets the concept of sustainability, offering the potential of renewability, biodegradation, and a path away from the problems associated with plastic derived from nonrenewable sources. As the biomaterials interest grows, the ecological impact of these postconsumer polymer products, when they enter into waste streams (landfill, compost, marine water, and sewage), does not contribute negatively toward the environment. The ultimate fate of biodegradable polymeric materials is focused on their conversion by microorganisms into final elemental products such as carbon dioxide, water, and new microbial biomass (i.e., mineralization). In this chapter, the necessary conditions for biodegradability of polymers, as well as the involved physical, chemical, and biological mechanisms, are reviewed. Various analytical techniques and standard test methods for evaluating the potential biodegradability and its toxicity level of polymeric materials in different environments are discussed in accordance with international standards and regulations.
Biofibres and Biocomposites
(Elsevier Ltd, 2008-02) John, Maya J; Thomas, S
This review deals with a recent study of the literature on the various aspects of cellulosic fibres and biocomposites. Cellulosic fibre reinforced polymeric composites are finding applications in many fields ranging from construction industry to automotive industry. The pros and cons of using these fibres are enumerated in this review. The classification of composites into green composites, hybrid biocomposites and textile biocomposites are discussed. New developments dealing with cellulose based nanocomposites and electrospinning of nanofibres have also been presented. Recent studies pertaining to the above topics have also been cited. Finally, the applications of cellulosic fibre reinforced polymeric composites have been highlighted
Biopolymer blends based on polylactic acid and polyhydroxy butyrate-co-valerate: effect of clay on mechanical and thermal properties
(Wiley, 2015-11) John, Maya J
Biodegradable polymer blends consisting of polylactic acid (PLA) and polyhydroxy butyrate-co-valerate (PHBV) have been prepared by melt mixing in a twin screw extruder and followed by injection molding technique. Cereplast PLA containing starch as an additive was used to make the blends. The effects of three different types of clay (montmorillonite, bentonite, and chemically modified bentonite) on the mechanical and thermal properties of the blends were studied. The ratio of PLA and PHBV (w/w) was maintained at 70:30 while the weight of clay was fixed at 1%. The addition of clay was found to result in a slight increase in tensile strength and modulus. Viscoelastic studies revealed that the damping property of the blends decreased with the addition of clay. This was attributed to the decreased segmental motion in the molecular chains. The morphology of the blends has been investigated by environmental scanning electron microscopy and a homogenous surface was observed for the blend containing montmorillonite.
Cellulose nanocrystals-based composites
(Scrivener Publishing LLC, 2020-01) Mokhena, Teboho C; John, Maya J; Mochane, MJ; Mtibe, Asanda; Motsoeneng, TS; Mokhothu, TH; Tshifularo, CA; Jamil, N; Kumar, P; Batool, R
Cellulose nanocrystals and cellulose nanocrystals-based composites with their unique features, such as abundance, renewability, high strength and stiffness, eco-friendliness, and relatively low density received unprecedented interest from both academia and industries as replacement of conventional petroleum-based materials, since conventional petroleum-based materials create ecological threats such as global warming and pollution. In this chapter, critical factors in the manufacturing of cellulose nanocrystals-based composites with regard to preparation methods, morphology, barrier and mechanical behaviour are comprehensively discussed. It concludes with the recent developments and future trends of cellulose nanocrystals reinforced biopolymers.
Cellulose nanomaterials: New generation materials for solving global issues
(2020-02) Mokhena, Teboho C; John, Maya J
This review describes the recent advances in the production and application of cellulose nanomaterials. Cellulose nanomaterials (CNMs), especially cellulose nanocrystals and cellulose nanofibers, can be produced using different preparation processes resulting in materials with unique structures and physicochemical properties that are exploited in different fields such as, biomedical, sensors, in wastewater treatment, paper and board/packaging industry. These materials possess attractive properties such as large surface area, high tensile strength and stiffness, surface tailor-ability via hydroxyl groups and are renewable. This has been a driving force to produce these materials in industrial scale with several companies producing CNMs at tons-per-day scale. The recent developments in their production rate and their applications in various fields such as medical sector, environmental protection, energy harvesting/storage are comprehensively discussed in this review. We emphasize on the current trends and future remarks based on the production and applications of cellulose nanomaterials.
Cellulosic fibril–rubber nanocomposites
(John Wiley & Sons (Asia) Pte Ltd, 2010-06) John, Maya J; Thomas, S
Cellulose is the most abundant polymer on earth- has emerged as an ideal candidate for providing nanoparticles as reinforcing agents. There is a growing interest in cellulose nanocomposites within the research community and especially if the composites are based on renewable resources. This chapter deals with various aspects of cellulosic nanofibre reinforced rubber nanocomposites. A brief description of cellulosic microfibrils and its properties is mentioned and some of recent studies dealing with cellulosic fibril reinforced rubber composites have been highlighted.
Chemical modification of flax reinforced polypropylene composites
(Elsevier Science B.V, 2009-04) John, Maya J; Anandjiwala, RD
This paper presents an experimental study on the static and dynamic mechanical properties of nonwoven based flax fibre reinforced polypropylene composites. The effect of zein modification on flax fibres is also reported. Flax nonwovens were treated with zein coupling agent, which is a protein extracted from corn. Composites were prepared using nonwovens treated with zein solution. The tensile, flexural and impact properties of these composites were analysed and the reinforcing properties of the chemically treated composites were compared with that of untreated composites. Composites containing chemically modified flax fibres were found to possess improved mechanical properties. The viscoelastic properties of composites at different frequencies were investigated. The storage modulus of composites was found to increase with fibre content while damping properties registered a decrease. Zein coating was found to increase the storage modulus due to enhanced interfacial adhesion. The fracture mechanism of treated and untreated flax reinforced polypropylene composites was also investigated from scanning electron microscopic studies
Comparison of interaction of aromatic solvents in hybrid and textile biocomposites
(SAGE Publications, 2009-11) John, Maya J; Thomas, S; Varughese, KT
Natural rubber was reinforced with sisal–oil palm hybrid fibers. Composites were prepared by varying the weight content of the fibers and chemical modification of the biofibers. The interaction of three different types of aromatic solvents, namely, benzene, toluene, and xylene with the rubber composites was analyzed. Textile composites were also prepared by sandwiching a single sheet of sisal fabric between two pre-weighed rubber sheets. The diffusion behavior of the textile composites in benzene, toluene, and xylene was also analyzed. The mechanics of diffusion was found to be different for hybrid and textile biocomposites. The swelling index factor was also calculated for all the composites. Swelling was found to be predominantly dependent on the aromatic solvent used and chemical treatments. Chemically modified composites were found to be less prone to solvent permeation
Composites from Natural Fibers and Bioresins
(Taylor & Francis, 2018-04) Paul, V; John, Maya J
There is an increasing urgency worldwide to develop bio-based products that can ease the widespread dependence on fossil fuels. The use of natural fibers and natural bio-based resin systems for the production of biocomposites has been pursued by researchers as they address environmental concerns. This chapter focuses on biocomposites produced from natural fibers and bio-resins, specifically using banana fibers and banana sap (BS)-based bio-resin. More importantly, natural fibers and bio-resins from agricultural waste were utilized to produce the biocomposites. The biodegradability tests of the biocomposite via respirometric methods confirmed that banana fiber with the BS bioresin degraded over a period of time.
Design and manufacturing of bio-based sandwich structures
(Wiley. Scrivener Publishing., 2017-03) John, Maya J
The aim of this chapter is to discuss the design and manufacturing of bio-based sandwich structures. As the economic advantages of weight reduction have become mandatory for many advanced industries, bio-based sandwich panels have emerged as preferred candidates as they possess interesting properties like high stiffness along with low weight. The work presents the background on sandwich panels highlighting the history and important advantages of sandwich structures. The different processing techniques for manufacture of sandwich panels are documented in detail. Bio-based sandwich panels are prepared by using bio-based skins (either a natural fiber skin impregnated with a thermoset resin or biopolymer skin bonded to the core with adhesives) or by using bio-based cores. The different types of bio-based core materials used in sandwich panels have been discussed. Case studies dealing with the preparation and characterization of bio-based sandwich panels have also been enumerated. Finally, the applications of sandwich panels in different industrial sectors are also discussed.
Dynamic mechanical and dielectric behavior of banana–glass hybrid fiber reinforced polyester composites.
(SAGE Publications, 2009) Pothan, LA; George, CN; John, Maya J; Thomas, S
Hybrid composites of glass and banana fiber (obtained from the pseudo stem of Musa sapientum) in polyester matrix, are subjected to dynamic mechanical analysis over a range of temperature and three different frequencies. The effect of temperature on the storage modulus(E’), loss modulus (E’’), and loss factor or damping efficiency (tan delta) is determined. All the properties are compared with those of the neat polyester samples and the un-hybridized composites. The effects of the layering pattern of the two fibers on the ultimate viscoelastic behavior of the composites are also investigated. Composites are prepared with banana as the surface layer and glass as the surface layer and also as an intimate mixture of glass and banana. At temperatures above Tg, the storage modulus values are found to decrease even with the addition of glass fiber for the geometry where glass is the core material. The value of the storage modulus of the composites with the above mentioned geometry is found to be different, above and below Tg, the value above Tg being lower than that below Tg unlike in unhybridized composite. The loss modulus curves and the damping peaks are found to be flattened by the addition of glass. Layering pattern or the geometry of the composites is found to have a profound effect on the dynamic properties of the composite. An intimately mixed composite is found to have the highest storage modulus values in all compositions. The values are consistent with the results of tensile strength. The tan delta curve is found to be affected by the layering pattern followed and gives insight into the interaction in the material. The dielectric behavior of the composites are also found to be dependent on the glass fiber volume fraction as well as the layering pattern employed. The study reports on the effect of hybridization on the dynamic mechanical behaviour as well as electrical properties of banana–glass composites. Hybridization of banana fiber with glass fiber has been proved to improve the mechanical performance and the water absorption behavior of the composites. The effect of the relative glass volume fraction as well as the layering patterns on the properties of the composites like storage modulus, loss modulus, and damping peaks are reported in the present communication. The nature of the storage modulus and damping peaks give an idea about the load transfer efficiency between the polymer and the reinforcement. The layering pattern giving best properties is proposed to be optimized based on the dynamic mechanical response of the composites
Effect of amphiphilic coupling agent on heat flow and dielectric properties of flax – polypropylene composites
(Elsevier, 2012-03) John, Maya J; Tlili, R; Anandjiwala, RD; Boudenne, A; Ibos, L
The study on heat transport in composites is of fundamental importance in engineering design and for tailoring thermal and mechanical behaviour of materials. In this study, the thermal conductivity and thermal diffusivity of flax reinforced polypropylene (PP) composites were determined at room temperature. Chemical modification in the form of a biodegradable zein coating was applied to the flax nonwovens. The effect of fibre loading and chemical modification on the thermo-physical properties was investigated. Dielectric permittivity studies were also evaluated and the dielectric constant of fibre reinforced composites was found to be higher than that of PP. The heat flow and crystallinity effects of the composites were also determined by differential scanning calorimetric (DSC) studies. Zein modification of the flax fibres resulted in a decrease of thermal conductivity and diffusivity which was attributed to a decrease in velocity and mean free path of phonons due to increase in interfacial adhesion.

Browsing by Author "John, Maya J"

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