Papers by Author: Krishnan Jayaraman

Abstract: Rotational moulding (RM) of plastics is predominantly used to produce hollow, singlepiece products. Polyethylene (PE) in its various forms, is the most commonly used material for this process. Researchers have been conducting numerous experiments trying to incorporate reinforcements attempting to improve the mechanical performance of RM products and overcome the material limitations posed by design parameters. One of the most common problems with reinforcement in RM is the migration of the filler towards the inside of the mould and agglomerations. In order to find a competitive material which is desirable by industry, RM experiments were conducted with various composite reinforcements; high density polyethylene (HDPE), numerous types of glass fibres (GF), carbon fibres (CF) and carbon nanotubes (CNT). In particular, the influence of low weight fractions of reinforcement on the mechanical performance, tensile, flexural and impact properties of HDPE were investigated.

Abstract: In this study, the physical properties of thermoplastic composites manufactured from linear medium density polyethylene (LMDPE), rice husk (RH) and maleic anhydride polyethylene (MAPE) were evaluated. Composites were manufactured with RH loadings of 15 wt%, 30 wt% and 50 wt% with 1 wt% of MAPE to investigate the effect of RH loading on the physical properties (water absorption and thickness swelling) of the composites. The results show that the water absorption and the corresponding thickness swelling increased with an increase in RH loading. Further manufacturing was carried out with 50 wt% of RH and 1wt%, 3.5 wt% and 6 wt% of MAPE to evaluate the effects of interfacial modification on the physical properties of the composites. The results show that the composites with 3.5 wt% of MAPE had least water absorption and the corresponding thickness swelling, whereas the composites having 1 wt% of MAPE had maximum water absorption and the thickness swelling. It can be concluded from these experiments that fibre loading as well as interfacial modification play a significant role in determining the physical properties of the composites.

Abstract: The compressive and flexural performance of flax fibre reinforced polymer (FFRP) confined coconut fibre reinforced concrete (CFRC) structures were investigated. The mass content of coconut fibre considered was 1% of cement. Eighteen cylinders were tested under uniaxial compression and 12 beams were tested under four-point bending. Test results show that in compression, both FFRP tube and FFRP wrapping confinements enhance the axial compressive strength and ultimate strain of concrete significantly, e.g. the ultimate strength of 4-layer FFRP tube confined CFRC is 94% larger than that of the unconfined CFRC. In flexure, the FFRP tube increases the lateral load bearing capacity and the deflection several times larger than the unconfined concrete columns, e.g. the ultimate lateral load of 4-layer FFRP confined PC and CFRC are 1066% and 946% larger than the corresponding unconfined PC and CFRC specimens. In flexure, coir inclusion can affect the failure mode of the FFRP-CFRC composite structure significantly.

Abstract: ncreasing environmental awareness has led to an increase in the usage of wood plastic composites in many countries. The primary objective of this research was the decrease in the density of wood particle-polypropylene composites using chemical blowing agents while retaining their mechanical properties. Different amounts of Azodicarbonamide (0%, 1% and 2% by weight) were mixed with four blends consisting of wood particles (15%, 25%, 35% and 45% by weight), Epolene (2% by weight) and polypropylene and compounded in an extruder. The resulting extrudates were granulated, injection-moulded into specimens and tested for density, tensile strength and impact strength. The secondary objective of this research was the increase in the electrical conductivity of wood particle-polypropylene composites using conducting agents for novel end usages. Different amounts of carbon black (1%, 3%, 5%, 7% and 10% by weight) were mixed with a blend consisting of wood particles (45% by weight), epolene (2% by weight) and polypropylene and compounded in an extruder. The resulting extrudates were granulated, compression-moulded into plates, machined into specimens and tested for electrical conductivity and tensile strength.

Abstract: In recent years, the use of agro-wastes, such as rice husk (RH), in the manufacture of thermoplastic composites to replace wood fibres has emerged as a promising field of interest. Linear medium density polyethylene (LMDPE) and ground rice husk (GRH) were used to manufacture composites. The D-optimal design routine in Design Expert software was used to select ten different blends with different percentages of RH, MDPE and compatibiliser, maleated polyethylene (MAPE) along with four replicate blends. RH was varied between 15 to 50 wt%, MAPE between 1 to 6 wt% and MDPE between 44 to 84 wt%. The effects of RH, MDPE and MAPE content on the mechanical properties of the manufactured composites were examined. The results show that tensile and flexural properties of the composites were improved, whereas, Charpy impact strength was decreased with increasing RH loading. The effect of MAPE on tensile strength and Charpy impact strength was significant, but its effect was negligible on tensile modulus, flexural strength and flexural modulus of the composites.

Abstract: Wastes such as saw dust (Pinus Radiata) and milk bottles (High Density Polyethylene - HDPE) are available in abundance. Composite decking materials, consisting of different weight percentages (60%, 70% and 80%) of saw dust and recovered HDPE, were extruded using a co-rotating, conical, twin screw extruder with a decking-profile die. The extruded decking materials were evaluated on their surface finish and shape conformance. The extruded decking materials were tested in accordance with the appropriate ASTM standards to determine their water absorption, thickness swell, static coefficient of friction, weathering and flexural (four-point bending) properties after they met the required quality ratings.

Abstract: Wastes such as saw dust (Pinus Radiata) and milk bottles (High Density Polyethylene - HDPE) are available in abundance. HDPE bars and composite bars, consisting of different volume percentages (50%, 60% and 70%) of saw dust and recovered HDPE, were extruded using a co-rotating, conical, twin screw extruder with a slit-profile die and an innovative sizing-cooling box. The extruded bars were evaluated on their surface finish, shape conformance and materials distribution across the cross-section. Mechanical testing of the extruded bars was carried out using appropriate ASTM standards after they met the required quality ratings.

Abstract: Natural fibres, such as sisal, flax and woodfibres, are relatively inexpensive and originate from renewable resources. Thermoplastic polymers, such as polypropylene (PP), high density polyethylene (HDPE) and waste plastics, possess shorter manufacturing cycle times and reprocessability. Natural fibre-reinforced thermoplastic composite materials exhibit favourable values of modulus and strength when the fibres are properly compounded with the polymers. Common methods for manufacturing natural fibre-reinforced thermoplastic composites, injection moulding and extrusion, require pre-compounding of the fibres and the thermoplastic due to the large difference in densities of the loose fibres and thermoplastic materials. Development and analysis of a screwless extruder that employs a reliable and low technology process for melt blending natural fibres and thermoplastic polymers is the main objective of this study.

Abstract: Rotational moulding or rotomoulding is a manufacturing process best suited for producing one-piece, hollow plastic products. The raw materials can be in powder or liquid form with linear polyethylene of varying densities being dominant worldwide. Due to the modest material properties of polyethylene, reinforcement in various forms have been incorporated within the rotomoulded components to improve the performance of these products. With the abundance and eco-friendliness of natural fibre resources, this study has focused on the use of sisal and woodfibres along with linear medium density polyethylene (LMDPE) powder to produce rotomoulded composite components. Tensile and impact properties of the rotomoulded natural fibre-reinforced composites have been determined as a function of fibre content.