Carbon nanotubes induced crystallization of poly(ethylene terephthalate)

We have investigated the crystallization characteristics of melt compounded nanocomposites of poly(ethylene terephthalate) (PET) and single walled carbon nanotubes (SWNTs). Differential scanning calorimetry studies showed that SWNTs at weight fractions as low as 0.03 wt% enhance the rate of crystallization in PET, as the cooling nanocomposite melt crystallizes at a temperature 10 °C higher as compared to neat PET. Isothermal crystallization studies also revealed that SWNTs significantly accelerate the crystallization process. WAXD showed oriented crystallization of PET induced by oriented SWNTs in a randomized PET melt, indicating the role of SWNTs as nucleating sites.

Polymer Nanocomposites: Crystallization, Reinforcement and Conductivity through SWNTs

The current research investigates the possibility of using single walled carbon nanotubes (SWNTs) as filler in polymers to impart several properties to the matrix polymer. SWNTs in a polymer matrix like poly(ethylene terephthalate) induce nucleation in its melt crystallization, provide effective reinforcement and impart electrical conductivity. We adopt a simple melt compounding technique for incorporating the nanotubes into the polymer matrix. For attaining a better dispersion of the filler, an ultrasound assisted dissolution-evaporation method has also been tried. The resulting enhancement in the materials properties indicates an improved disentanglement of the nanotube ropes, which in turn provides effective matrix-filler interaction. PET-SWNT nanocomposite fibers prepared through melt spinning followed by subsequent drawing are also found to have significantly higher mechanical propertiesas compared to pristine PET fiber.SWNTs also find applications in composites based on elastomers such as natural rubber as they can impart electrical conductivity with simultaneous improvement in the mechanical properties.

Modification of Polyethylenes by Reactive Extrusion

The main aim of the study was to optimise the reactive extrusion conditions in the conventional modification processes of polyethylenes in a single screw extruder.The optimum conditions for peroxide crosslinking of low density polyethylene (LDPE), linear low density polyethylene (LLDPE) and their blend were determined in a torque rheometer. The actual reactive extrusion was performed in a laboratory single screw extruder using the optimum parameters. The influence of the coagent, triaUyl cyanurate (TAC), on the cross linking of low density polyethylene in the presence of peroxide was also investigated. The peroxide crosslinking was found to improve the mechanical properties and the thermal stability of the polyethylenes. The efficiency of crosslinking was found to be improved by the addition of coagent such as TAC.The optimum conditions for silane grafting viz temperature, shear rate, silane and DCP concentrations were determined on a torque rheometer in the case of LDPE, LLDPE and their blend. Silane grafting of LDPE in the presence of peroxide was performed with and without addition of water. Compounding of such mixtures in the melt at high temperatures caused decomposition of the peroxide and grafting of alkoxy silyl groups to the polyethylene chains.The optimum parameters for maleic anhydride modification of LDPE, LLDPE and their blend were determined. The grafting reaction was confinned by FTIR spectroscopy. Modification of polyethylenes with maleic anhydride in the presence of dicumyl peroxide was found to be useful in improving mechanical properties. The improvement was found to be mainly due to the grafting of carboxyl group and formation of crosslinks between the chains. The cross linking initiated improvements indicate extended property profiles and new application fields for polyethylenes.On the whole the study shows that the optimum conditions for modifying polyethylenes can be determined on a torque rheometer and actual modification can be performed in a single screw extruder by employing the optimum parameters for improved mechanical! thermal behaviour without seriously affecting their processing behaviour.

Reactive loaded microstrip leaky wave antenna for low cost beam steering applications

A novel fixed frequency beam scanning microstrip leaky wave antenna is reported. The beam scanning at fixed frequency is achieved by reactive loading. Simulation and measured results shows frequency scanability of 80° as well as fixed frequency beam steering of 68° over the −10 dB impedance band of 4.56–5.06 GHz.

On the crystallization kinetics and micro-structural transformations of Fe40Ni38B18Mo4 alloys

Activation energy for crystallization (Ec) is a pertinent parameter that decides the application potential of many metallic glasses and is proportional to the crystallization temperature. Higher crystallization temperatures are desirable for soft magnetic applications, while lower values for data storage purposes. In this investigation, from the heating rate dependence of peak crystallization temperature Tp, the Ec values have been evaluated by three different methods for metglas 2826 MB (Fe40Ni38B18Mo4) accurately. The Ec values are correlated with the morphological changes, and the structural evolution associated with annealing temperatures is discussed.

Studies on the Solvent Dependence in the Reaction of a Few (Anthracen-9-yl)MethyLamines and Sulfanes with Reactive Acetylenes

The thesis entitled ‘Studies on the Solvent Dependence in the Reaction of a Few (Anthracen-9-yl)methylamines and Sulfanes with Reactive Acetylenes’ is divided into six chapters. ln Chapter l a general survey of electron transfer reactions, Diels-Alder reactions and Michael-type additions is presented. A detailed discussion on the synthesis of several (anthracen-9-yl)methylamines is presented in Chapter 2. In Chapter 3, results of preliminary photophysical studies on a few (anthracen-9yl) methylamines are compiled. A detailed discussion on extensive examination of dependence in the reaction of (anthracen-9-yl)methylamines with reactive acetylenes is presented Chapter 4. Details on the synthesis and reaction of a few (anthracen-9-yl)methylsulfanes with DMAD are described in Chapter 5.

Reactive pozzolanas from rice husk ash: An alternative to cement for rural housing

This paper discusses the properties of rice husk ash samples produced from different types of field ovens to compare the performance of the ovens and to identify the most feasible method to produce a reactive pozzolana as an alternative to cement for building applications requiring lower strengths. Different types of ashes are produced and long-term strength of rice husk ash pozzolanas with lime or cement is investigated to suggest a sustainable affordable option in rural building applications, especially for rural housing in Kerala, a southern state of India