Research Group - BITS Pilani

Doctoral Students ( Completed)

Left to Right: Mukund Harugade, Amal Siju, Sachin Waigaonkar, Pozhil S N and Honey Srivastava

Girish Chandran

Title of Ph.D. thesis: Investigations on Rheological and Thermomechanical Properties ofLLDPE - Fumed SilicaNanocomposites for Rotational Molding.

Status: Completed in September 2016

Abstract: This research work is focused on experimental investigations of RM of LLDPE - FS nano composites to improve the melt flow characteristics of the polymer as well as mechanical properties of the product. Melt flow index (MFI) is commonly used to ascertain the melt characteristics of thermoplastic polymers. For RM using LLDPE, MFI values between 3.5 to 5 g/10 min (at 2.16 kg/190 deg C) are preferred. The MFI values of LLDPE and FS blends were measured and proper blends for RM were identified. RM being a low shear process, parallel plate rheometry studies were conducted to study the melt rheology of LLDPE - FS blends and zero shear viscosity was found out. Based on the zero shear viscosity inferences were drawn about the interaction between the nano particles and LLDPE chains. In order to analyze the variations in melt torque during compounding of LLDPE, torque rheometry studies were performed. The effect of FS on the mechanical and visco elastic properties of LLDPE has been further investigated. It included the effect of FS on static mechanical properties of RM product like tensile, flexural, and impact strengths. The effect of FS on crystallinity of LLDPE is studied by conducting X-ray diffraction studies. The micro structural studies using scanning electron microscopy were conducted to study the dispersion of FS in LLDPE and correlated with the mechanical properties of the nano composites. Dynamic mechanical analysis (DMA) was also carried out to find the time – temperature dependent mechanical properties viz. storage modulus , loss modulus , and tan delta for LLDPE - FS blends.

DMA studies were extended to perform accelerated stepped isothermal creep studies to find out the influence of FS on creep strains. As RM suffers a drawback of longer cycle times, the effect of FS on the processibility was also studied apart from the material properties and attempts were made to reduce the cycle time. This was done by preparing an innovative fixture with internal heating and temperature monitoring capabilities, that can be used on a standard universal testing machine. The mold release force was measured for both steel and aluminum molds at different temperatures and pulling rates. The cycle time reduction was achieved by finding minimal pulling force for successful demolding at higher temperatures than (currently) used in industry.
Having arrived at a suitable LLDPE - FS composition at laboratory scale, the same was tested for an engineered product at industrial scale.

The industry trials were conducted using a three arm bi-axial rotational molding machine by carefully monitoring the internal air temperature within the mold at GMI Zarahak Moulders Pvt. Ltd, Goa. The effect of 4% FS on powder flow quality (dry flow and bulk density), MFI, static mechanical properties (tensile strength, modulus, toughness, flexural strength and impact strength) as well as dynamic mechanical properties (storage and loss modulus), along with creep and relaxation were investigated. Morphological studies were conducted to correlate the above findings with the dispersion of the nano particles within LLDPE matrix.

Finally, the comparative studies between the laboratory findings and scaled up industry trials have been carried out.
Since rotational molding industry is looking for alternative and newer materials with improved properties, the proposed research work is expected to be beneficial to industry as well as the society as majority of the rotationally molded products are used in infrastructural applications.

Hari Chandekar

Thesis title: Investigation of Mechanical and Creep Behaviour of Jute Fibre-Polypropylene Composites

Supervisor: Dr. Vikas Choudhari , Co-Supervisor: Dr. Sachin Waigaonkar

Status: Completed on March 1, 2022

Abstract of the thesis:

The natural fibre composites are gaining wide popularity due to their environmental sustainability over synthetic fibre reinforced composites. These composites are finding promising applications in the automotive, construction as well as in consumer goods sector. The jute fibres are abundant, low in cost, and non-abrasive to the tooling during processing. The polymer composites comprising recyclable polymers like polypropylene (C3H6)n reinforced with short jute fibres can be a good option as they are CO2 neutral in terms of energy requirement for production.
The interfacial bonding of hydrophilic jute fibres with hydrophobic PP matrix can be improved by different chemical treatments. During the present investigations different chemical treatments such as alkali, silane, potassium permanganate and coupling agent viz. maleic anhydride grafted PP have been used with jute fibres. The different chemical treatments carried out on jute fibres were characterized using Fourier Transform Infrared (FTIR) Spectroscopy and Field Emission Scanning Electron Microscopy (FESEM) techniques to check the effectiveness of the chemical treatment on the fibres. The chemically treated jute fibres were blended with PP in a co-rotating twin screw extruder in different weight fractions 5wt%, 10wt%, 20wt%, 30wt% and the jute-PP composites were prepared using injection moulding process to study the effect of chemical treatment on the mechanical properties namely tensile, flexural, impact and microhardness.
The natural fibres inherently possess hydrophilic nature and are capable of absorbing water, which adversely affects the physical and mechanical properties of the composites. Hence, the effect of different chemical treatments on the moisture absorption characteristics of the jute-PP composite was carried out. The tests were conducted for a long duration of time, approximately 150 days. The water diffusion coefficient of the jute-PP composite was determined using the approximate solution of Fick’s model.
The behaviour of the composite under constant loading for prolonged period is important due to the viscoelastic nature of the polymer matrix. Therefore, the creep and recovery behavior of the jute-PP composites was studied in a typical 3-point bending configuration using Dynamic Mechanical Analyzer (DMA). The creep behaviour of the jute-PP composites was modeled using four-parameter Burger’s model and compared with classical power law model. To model the recovery behaviour, Weibull distribution function was used. Furthermore, the time-temperature superposition (TTS) principle was employed for predicting the long-term creep behaviour of the chemically treated jute-PP composites.
To account for the random nature of short fibres in the composite, a computationally inexpensive 2D finite element (FE) model has been proposed for random location and orientation of fibres with constant aspect ratio. Random sequential adsorption (RSA) algorithm was implemented in Matlab® to generate the representative volume element (RVE) of randomly distributed jute-PP composite. The simulation of the composite elastic behaviour was carried out in ABAQUS®. The validation process of FE model using experimental findings has been described. Finally, FE model results were compared with the results obtained by theoretical models.

Mukund Hargude

Thesis title: Experimental Investigations and Analysis of Magnetic field Assisted Electrochemical Discharge Machining Process

Status: Completed on June 23, 2023

Abstract:

Miniaturized products have been increasingly popular in recent years all across the world. The demand for small, versatile, interconnected micro items has been continuously growing. There is high demand in the fields of automobiles, airplanes, spacecraft, biomedical, sports, irrigation systems, electronic components, telecommunications, robotics, and micro-electromechanical systems (MEMS), among others. Sometimes to make a miniature product, small parts of non-conductive materials such as glass, ceramics, and composites are required. These small parts are made using techniques such as micro-molding, micro-welding, micromachining, and micro cold forming. As a result, different non-traditional and hybrid machining techniques have been introduced, to machine hard and difficult-to-cut materials.
Electrochemical discharge machining (ECDM) is the hybrid machining process, which is used for machining of non-conductive materials. It is a combination of the electric discharge machining (EDM) and electro chemical machining process (ECM). Different ECDM variants have been developed such as drilling, milling, grinding, turning, trepanning, sinking, wire cutting, and trueing. These ECDM variants are successfully used for machining of the glass, ceramics and composites. Nevertheless, these variants of ECDM are used as primary machining process.
After the conventional drilling of composite, formation of delaminated fibers is the common phenomena. To remove these delaminated fibers, ECDM has been used as secondary finishing operation like a deburring process. ECDM process has been firstly implemented for removing the delaminated fibers. So, to Improve the machining process; two machining methods (top edge and inside edge machining) along with magnetic field were employed. Comparative studies were conducted with conventional drilling operations and inferences were made.

Amal Siju

Thesis Title: Experimental analysis on the performance and effects of textured carbide inserts in dry turning of Ti64 alloy.
Status: Completed on August 24, 2023
Abstract: The application of tool texturing has been emerged as a promising research front to attain better tribological properties in machining. Despite the benefits of micro-structured tools being established, manufactures are yet to implement the same on turning inserts. This research work involves the experimental analysis of textured cutting tools in machining hard materials( Ti alloys in particular) and testing its adequacy. A detailed comparative study is made on the effect of texture geometries, its shape, size and spacing on various cutting parameters. A comparison was also made between non-textured and textured inserts, emphasizing the performance of the textured inserts under different cutting regimes. The design and fabrication of an innovative duel-textured inserts used in machining Ti-6Al-4V, showed a significant reduction in cutting forces and coefficient friction over other texture patterns. Analytical models were developed to calculate the cutting force and relate the changes in length of contact while using textured tools in machining operations. SEM and microscopic characterization of tool flank, rake surface and chips were also performed in this study. The observed reduction cutting forces and other cutting parameters were also correlated to the surface roughness, cutting temperature, chip segmentation, etc. A few key conclusions are made on overwhelming studies on tool texturing and real-life applications of textured inserts based on the obtained results.

Pozhil S N

Title of Thesis (Proposed): Investigation of Creep and Fracture Behaviour of Rotationally Mouldable Polypropylene
Status: Completed on November 2, 2023
Co-Supervisor: Dr. Vikas Choudhari
Abstract:

Rotational moulding, a versatile polymer processing technology, is the preferred method for producing hollow domestic and complex engineered products, usually of large dimensions. As a fast-growing field, the requirement for new materials to be processed by this method is increasing; polypropylene has attracted the global rotational moulding community as it has better mechanical properties in load-bearing applications. This research is focused on investigating the creep and the fracture behavior of rotationally moulded polypropylene. Investigating these behaviours aims to provide rotomoulders the required data for designing products that would perform satisfactorily over several decades.

Following the completion of his Ph.D., Pozhil established his own industry. More details can be found at the following link:

https://www.valamaipolymers.in/index.html

Honey Srivastava

Title of Thesis : Composites Based on Human Hair and Poly(methyl methacrylate): Preparation and Investigations of their Thermal, Physico-chemical and
Mechanical Properties”
Supervisor: Dr. Rashmi Chouhan, Dept of Chemistry
Co-Supervisor: Dr. Sachin Waigaonkar
Status: Completed on May 27, 2024

The global synthetic fibers industry is valued at approx. 51000 million US $. Most synthetic fibers are derived from petrochemical sources. The Natural fibers derived from plants and animals are cheap, renewable, and environment-friendly alternatives to synthetic fibers. The inferior mechanical and chemical properties of natural fibers limit their applications. Over the last few years, many efforts have focused on valorizing keratin-based waste.
Human hair (HH) is a proteinaceous fiber with strongly bonded peptide subunits from the α-keratin chains. HH is an eco-friendly material that can be used for the development of green composites because of its properties such as biodegradability, biocompatibility and fire retardant capability. Its high sulfur content increases the resistance towards different chemical agents.Graft copolymerization of vinyl monomers such as methacrylate, methyl
methacrylate (MMA), and methacrylic acid is one of the effective and accessible methods of chemical modification of high molecular weight compounds, natural polymers in particular. Therefore, there is a huge scope to explore the chemical modification of human hair via grafting and its use as reinforcement in poly(methyl methacrylate) (PMMA) composites.The surface of human hair has been modified via grafting of poly(methylmethacrylate). The grafting has been done via free radical polymerization using “graft from”approach. The percentage grafting increased with the increase in concentration of MMA in
feed. At feed ratio of 1:2::HHact:MMA, complete coverage of HH surface was observed. FT-IR, Raman, and SEM confirmed the grafting. Graft copolymers shows improved thermal andmechanical properties. The cross-linker was added during polymerization, which improves the tensile strength and stiffness of the graft copolymers.The possibility of using human hairs, which are waste materials, as an alternative to synthetic fibers for the enhancement of some mechanical properties of the PMMA matrix was also studied. Virgin and graft copolymers of human hairs were used as a reinforcement for the preparation of poly(methyl methacrylate) composites. Human hairs were grafted using Methyl Methacrylate (MMA) via free radical polymerization in feed ratio of 1:2 and
1:1.75::HHact:MMA. PMMA composites reinforced with virgin and graft copolymers of HH vii were fabricated by compression moulding technique by varying the fiber weight fractions(15%, 30%, 45%, and 60%). The influence of graft copolymerization and fiber loading on the mechanical properties of PMMA composites were investigated. The graft copolymer reinforced composites have a greater ability to support stress transfer from the polymer matrix compared to virgin HH. Grafting also plays a major role in the mechanical properties of composites and provides better interfacial interaction between the matrix and fiber surface. The physicochemical properties of graft copolymers, such as chemical stability in acidic and basic media, swelling behavior in water, and also the adsorption properties towards cationic and anionic dyes such as methylene blue (MB) and methyl orange (MO), have been discussed in detail. The adsorption capacity (qe) and removal efficiency (η) of grafted copolymers were at par with the qe and η of virgin HH and HHact for methyl orange, but a
substantial increase in qe and η was observed for grafted copolymers as compared to HHact for MB dye. Therefore, these graft copolymers can also potentially act as the adsorbent material for removing dyes such as from contaminated waters.

Doctoral Students ( Ongoing)

Savardekar Umakant Nivrutti

Proposed Title: Investigations of Graphene Based Nano Composites for Rotational Molding.

Co-Supervisor: Prof. Vikas Choudhari

Abstract: In recent years, Graphene has emerged as a preferred material in the polymer industry for developing nanocomposites due to its exceptional electrical, thermal, mechanical, and gas barrier properties when combined with polyolefins. This study focuses on the application of Graphene nanocomposites in rotational molding, examining the sintering characteristics of polyethylene (PE) nanocomposites, which are crucial for producing high-quality, porosity-free parts in rotational molding. The research will be conducted using a typical industrial setup, and will also evaluate how incorporating graphene enhances properties such as gas and chemical barrier resistance, flammability, flame spread, and service temperature for rotomolding applications.

Mr Umakant Savadekar (BE (Mech), M tech Nano sci.) is Managing Director of Phychem Technologies Pvt. Ltd. The details can be found in the following link:

https://www.phychem.com/index.html

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