Study on acceleratore in rubber vulcanization with special reference to the binary systems containing substituted dithiobiurets

The thesis entitled Study on Accelerators in Rubber Vulcanization with Special Reference to the Binary Systems Containing Substituted Dithiobiurets. It includes a detailed study on the binary accelerator systems containing substituted dithiobiurets in natural rubber and NR latex and dithiobiurets in SBR and NR-SBR blends vulcanization systems. It deals with the experimental procedure adopted for the preparation of DTB-II and DTB-III; the procedure for compounding and vulcanization and determination of physical properties like modulus, tensile strength, elongation at break, hardness, compression set, heat build up etc. The results indicate that there is efficient acceleration activity of the dithiobiurets in the vulcanization of natural rubber latex containing TMT. The study of dithiobiurets in natural rubber and NR latex reveal that they are having definite accelerating effect in SBR vulcanization systems.

Investigations on polyaniline based systems for technologically important applications and some novel polymers as prospective candidates for fabricating polymer light emitting diodes

Light emitting polymers (LEP) have drawn considerable attention because of their numerous potential applications in the field of optoelectronic devices. Till date, a large number of organic molecules and polymers have been designed and devices fabricated based on these materials. Optoelectronic devices like polymer light emitting diodes (PLED) have attracted wide-spread research attention owing to their superior properties like flexibility, lower operational power, colour tunability and possibility of obtaining large area coatings. PLEDs can be utilized for the fabrication of flat panel displays and as replacements for incandescent lamps. The internal efficiency of the LEDs mainly depends on the electroluminescent efficiency of the emissive polymer such as quantum efficiency, luminance-voltage profile of LED and the balanced injection of electrons and holes. Poly (p-phenylenevinylene) (PPV) and regio-regular polythiophenes are interesting electro-active polymers which exhibit good electrical conductivity, electroluminescent activity and high film-forming properties. A combination of Red, Green and Blue emitting polymers is necessary for the generation of white light which can replace the high energy consuming incandescent lamps. Most of these polymers show very low solubility, stability and poor mechanical properties. Many of these light emitting polymers are based on conjugated extended chains of alternating phenyl and vinyl units. The intra-chain or inter-chain interactions within these polymer chains can change the emitted colour. Therefore an effective way of synthesizing polymers with reduced π-stacking, high solubility, high thermal stability and high light-emitting efficiency is still a challenge for chemists. New copolymers have to be effectively designed so as to solve these issues. Hence, in the present work, the suitability of a few novel copolymers with very high thermal stability, excellent solubility, intense light emission (blue, cyan and green) and high glass transition temperatures have been investigated to be used as emissive layers for polymer light emitting diodes.

Synthesis, Characterization and Application Studies of Some Polymer Supported Metal Complexes

Polymer supports and polymeric complexes are highly versatile and they are successfully employed as efficient reagents, substrates and catalysts. Recently there observed a growing interest in the synthesis of tailor-made polymer supports and functionalized polymers for the preparation of metal complexes for various applications. They have the combination of properties due to the macromolecular structure as well as due to the reactivity of the functional group. An interesting feature of functional polymers is their affinity towards metal ions. Therefore the synthesis, characterization and application of such polymeric complexes have great scientific and analytical importance. In this investigation three series of polymeric complexes of transition metal ions are prepared from three schiff bases. All the complexes and polymeric schiff bases were characterized by analytical, spectral and thermal methods The thesis consist of six chapters. The first chapter contains an introduction and a brief review on application of polymer supports, polymer supported ligands and complexes. The second chapter gives the details of reagents and instruments used and the procedure adopted for the preparation of ligands and complexes. The third chapter explains the methods employed for characterization and the results are also discussed. The fourth chapter gives a detailed study of metal ion removal using ligands whereas the fifth chapter describes the development of the Cu” ion sensor electrode. The sixth chapter is the summary of the thesis and references are presented at the end.

Synthesis, characterization and properties of Conductive elastomeric composites based on Polypyrrole and short Nylon-6 fiber

The search for new materials especially those possessing special properties continues at a great pace because of ever growing demands of the modern life. The focus on the use of intrinsically conductive polymers in organic electronic devices has led to the development of a totally new class of smart materials. Polypyrrole (PPy) is one of the most stable known conducting polymers and also one of the easiest to synthesize. In addition, its high conductivity, good redox reversibility and excellent microwave absorbing characteristics have led to the existence of wide and diversified applications for PPy. However, as any conjugated conducting polymer, PPy lacks processability, flexibility and strength which are essential for industrial requirements. Among various approaches to making tractable materials based on PPy, incorporating PPy within an electrically insulating polymer appears to be a promising method, and this has triggered the development of blends or composites. Conductive elastomeric composites of polypyrrole are important in that they are composite materials suitable for devices where flexibility is an important parameter. Moreover these composites can be moulded into complex shapes. In this work an attempt has been made to prepare conducting elastomeric composites by the incorporation of PPy and PPy coated short Nylon-6 fiber with insulating elastomer matrices- natural rubber and acrylonitrile butadiene rubber. It is well established that mechanical properties of rubber composites can be greatly improved by adding short fibers. Generally short fiber reinforced rubber composites are popular in industrial fields because of their processing advantages, low cost, and their greatly improved technical properties such as strength, stiffness, modulus and damping. In the present work, PPy coated fiber is expected to improve the mechanical properties of the elastomer-PPy composites, at the same time increasing the conductivity. In addition to determination of DC conductivity and evaluation of mechanical properties, the work aims to study the thermal stability, dielectric properties and electromagnetic interference shielding effectiveness of the composites. The thesis consists of ten chapters.

Investigations on novel polymer nano composites and bio-compatible manganese doped ZnS nanocrystals for photonic and bio-imaging applications

Fluorescence is a powerful tool in biological research, the relevance of which relies greatly on the availability of sensitive and selective fluorescent probes. Nanometer sized fluorescent semiconductor materials have attracted considerable attention in recent years due to the high luminescence intensity, low photobleaching, large Stokes’ shift and high photochemical stability. The optical and spectroscopic features of nanoparticles make them very convincing alternatives to traditional fluorophores in a range of applications. Efficient surface capping agents make these nanocrystals bio-compatible. They can provide a novel platform on which many biomolecules such as DNA, RNA and proteins can be covalently linked. In the second phase of the present work, bio-compatible, fluorescent, manganese doped ZnS (ZnS:Mn) nanocrystals suitable for bioimaging applications have been developed and their cytocompatibility has been assessed. Functionalization of ZnS:Mn nanocrystals by safe materials results in considerable reduction of toxicity and allows conjugation with specific biomolecules. The highly fluorescent, bio-compatible and water- dispersible ZnS:Mn nanocrystals are found to be ideal fluorescent probes for biological labeling

“Fabrication and characterization of polymer optical fibers for photonic device applications

Although the main application of optical fibers are in the field of telecommunication, optical fiber based sensors of various designs are becoming valuable devices for wide industrial applications. The advantages of optical fiber-based sensors include high sensitivity, insensitivity to electromagnetic radiation; spark free, light weight and minimal intrusiveness due to their relatively small size and deployment in harsh and hostile environments. It has been proved that POI-7 based sensors can be employed to detect a great variety of parameters including temperature, humidity, pressure, refractive index etc. The proposed thesis presented in six chapters deals with the work carried on dye doped and undoped POF for photonic device applications such as amplifier, laser and sensor

Effect of Feeding Rate in Polymer Extrusion ”

Starve feeding of single screw extruder was described as an important means of improving the performance characteristics of the extruder. In addition to such improvement with versatility, the starve feeding technique also may affect the mechanical properties of the extrudate since the heat transfer an(l mixing characteristics in the starve fed and Hood fed extruders are not the same. Since the material is more loosely packed in the channels of the starve fed extruder, there may be greater bed mobility and uniformity. Further, the. thermal an(l shear induced degradation are also less since possibilities of developing local high temperatures are less compared to a densely compacted extruder bed. This study has been undertaken mainly to explore the effect of feeding rate on the mechanical properties of rubber and plastic extrudates since the effect of feeding rate has not been analysed from this angle so far.

“Studies on new base materials for microcellular soles"

The most important part of any footwear is the sole (or sole and heel) which withstands all the hannful external factors such as rouglmess of the ground or road, sharp objects, thorns and stones, heat, dampness and cold during walking. The properties desirable in soling material, therefore, would be 1. lightness 2. resistance to wear and tear for long service life 3. flexibility/softness for wearing comfort 4. thennal insulation Rubber soling surpasses all other soling materials in better performance and lower cost. Because MC sole is soft and very light, and has good abrasion resistance, flex properties and set behaviour it has become very popular all over the world and demand for better quality product is ever increasing. Due to the traditional approach adopted by the footwear industry in foot wear design, the rubber based footwear export surprisingly contributes only a small percentage. The essence of success for any industry lies in the expansion of the export market. Microcellular soles are manufactured for the last three decades without much change in the traditional design and colour pattern. In recent years domestic customers have also started demanding better quality products. In view of the changing taste of the customer and growing competition from other countries, substantial improvement in the export potential will require new base materials for regular or fashion rubber based footwears. The main objective of the present study is to develop new base materials for making MC soles with good quality, viz., light weight, durability and bright colours

Biodegradability Studies on LDPE-Starch Blends using Amylase-Producing Vibrios

Low-density polyethylene, (LDPE) was mixed with two grades of tapioca starch–lowgrade and high-grade. Various compositions were prepared and mechanical and thermal studies performed. The biodegradability of these samples was checked using a culture medium containing Vibrios (an amylase-producing bacteria), which was isolated from a marine benthic environment. The soil burial test and reprocessability of these samples were checked. The studies on biodegradability show that these blends are partially biodegradable. These low-density polyethylene-starch blends are reprocessable without sacrificing much of their mechanical properties

Polymer-Plastics Technology and Engineering

Fine (approximately 18 nm) particles of nickel ferrite were synthesized by the sol-gel technique, and their structural properties were evaluated by X-ray diffraction. Neoprene-based rubber ferrite composites were prepared by incorporating these nickel ferrite powders in the rubber matrix according to a specific recipe. The cure characteristics were analyzed, and the samples were molded into particular shapes whose properties were determined according to ASTM standards. Magnetization studies were carried out using a Vibrating Sample Magnetometer. This study indicates that neoprene rubber-based flexible magnets with desired magnetic properties and appropriate mechanical properties can be prepared by incorporating an adequate amount of nanoscale nickel ferrite particles within the rubber matrix

Microwave Absorption of Nylon 6,6 Based Polymer Ferrite Composites

Ferrite composites are magnetic composites consisting of fine particles of metal ferrites dispersed in the polymer matrix. These composites have a variety of applications as flexible magnets, pressure/photo sensors and microwave absorbers. Polymers and magnetic materials play a very important role in our day to day life. Both natural and synthetic polymers are today indispensable to mankind. The polymers, which include rubber, plastics and fibers, make life easier and more comfortable.

Epoxy-modiWed, unsaturated polyester hybrid networks

Hybrid polymer networks (HPNs) based on unsaturated polyester resin (UPR) and epoxy resins were synthesized by reactive blending. The epoxy resins used were epoxidised phenolic novolac (EPN), epoxidised cresol novolac (ECN) and diglycidyl ether of bisphenol A (DGEBA). Epoxy novolacs were prepared by glycidylation of the novolacs using epichlorohydrin. The physical, mechanical, and thermal properties of the cured blends were compared with those of the control resin. Epoxy resins show good miscibility and compatibility with the UPR resin on blending and the co-cured resin showed substantial improvement in the toughness and impact resistance. Considerable enhancement of tensile strength and toughness are noticed at very low loading of EPN. Thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA) and diVerential scanning calorimetry (DSC) were employed to study the thermal properties of the toughened resin. The EPN/ UPR blends showed substantial improvement in thermal stability as evident from TGA and damping data. The fracture behaviour was corroborated by scanning electron microscopy (SEM). The performance of EPN is found to be superior to other epoxy resins

Epoxidized Phenolic Novolac: A Novel Modifier for Unsaturated Polyester Resin

Unsaturated polyester resins (UPRs) are used widely in the fiber-reinforced plastics (FRPs) industry. These resins have the disadvantages of brittleness and poor resistance to crack propagation. In this study, hybrid polymer networks (HPNs) based on UPR and epoxidized phenolic novolacs (EPNs) were prepared by reactive blending. A HPN is composed of a backbone polymer containing two types of reactive groups that can take part in crosslinking reactions via different mechanisms. EPNs were prepared by glycidylation of novolacs using epichlorohydrin. The novolacs had varying phenol: formaldehyde ratios. Blends of unsaturated polyester with EPN were then prepared. The physical properties of the cured blends were compared with those of the control resin. EPN shows good miscibility and compatibility with the resin and improves the toughness and impact resistance substantially. Considerable enhancement of tensile strength is also noticed at about 5% by weight of epoxidized novolac resin. TGA, DMA, and DSC were used to study the thermal properties of the toughened resin and the fracture behavior was studied using SEM. The blends are also found to have better thermal stability. Blending with EPN can be a useful and cost-effective technique for modification of UPR

Amidino Thiourea as a Secondary Accelerator in Rubber Vulcanization

Earlier studies5773 in our laboratory showed that when a nucleophile is used along with disulphide or sulphenamide accelerators the vulcanization is accelerated greatly and the reaction mechanism is generally nucleophilic in nature. However it was observed that it also changes with the systems under review. The present study, deals with the use of unsubstituted amidino thiourea i.e. aminoimino methyl thiourea(AMT) V in the vulcanization studies of different elastorners and their blends. One of the aims of this study was to get further proof with regard to the theory of nucleophilic reaction mechanism in such binary systems.Mixes containing thiourea are used as controls. AMT is more nucleophilic than TU and this is clear from the fact that the fonner can condense with isothiocynate even in the absence of alkali while TU cannot". Also the guanidinyl group in AMT can facilitate the polarization of the C=S bond favouring a nucleophilic reaction

Spray pyrolysed In2S3 thin films: A potential electron selective layer for large area inverted bulk-heterojunction polymer solar cells

In this paper, we report the results of investigations on the potential of spray pyrolysis technique in depositing electron selective layer over larger area for the fabrication of inverted bulk-heterojunction polymer solar cells. The electron selective layer (In2S3) was deposited using spray pyrolysis technique and the linear heterojunction device thus fabricated exhibited good uniformity in photovoltaic properties throughout the area of the device. An MEH-PPV:PCBM inverted bulk-heterojunction device with In2S3 electron selective layer (active area of 3.25 3.25 cm2) was also fabricated and tested under indoor and outdoor conditions. Fromthe indoor measurements employing a tungsten halogen lamp (50mW/cm2 illumination), an opencircuit voltage of 0.41V and a short-circuit current of 5.6mA were obtained. On the other hand, the outdoor measurements under direct sunlight (74mW/cm2) yielded an open-circuit voltage of 0.46V and a short-circuit current of 9.37mA