T. K. Chaki

New Thermoplastic Elastomers from Poly(Ethylene-Octene) (Engage), Poly(Ethylene-Vinyl Acetate) and Low-Density Polyethylene by Electron Beam Technology: Structural Characterization and Mechanical Properties

Abstract New thermoplastic elastomers have been prepared from the blends of metallocene-based polyolefins (Engage) with low-density polyethylene (LDPE), and ethylene-vinyl acetate copolymers (EVA) of different grades with LDPE by electron beam modification. Structural changes of these blends with or without sensitizer in presence of irradiation have been evaluated by X-ray diffraction (XRD) and differential scanning calorimetry (DSC). Scanning electron microscopy (SEM) in conjunction with atomic force microscopy (AFM) indicate the soft rubber domain in the continuous plastic matrix. Significant improvements of mechanical, dynamic mechanical and set properties have been obtained by electron beam modification, retaining its reprocessibility characteristics. Effects of ditrimethylol propane tetraacrylate (DTMPTA) as radiation sensitizer have also been evaluated from the mechanical, dynamic mechanical properties and reprocessibility.

Temperature dependent electrical properties of Conductive Composites (Behavior at cryogenic temperature and high temperatures)

Extrinsically conductive polymer composites can be developed by incorporation of conductive filler in suitable polymer matrix. The formation of conductive network in insulating matrix due to filler aggregation at and above percolation is responsible for electrical conductivity of such composites. The present investigation deals with effect of temperature on conductive composites made from different blends of Ethylene-Vinyl copolymer (EVA) and Acrylonitrile-Butadiene copolymer (NBR) filled with particulate carbon filler. The electrical properties of these composites depend on blend composition and filler loading. High temperature (303-393K) DC-resistivity against temperature for EVA and EVA blends composites show positive coefficient of temperature (PCT effect) followed by negative coefficient of temperature (NCT effect) thus passing through a maxima which corresponds to crystalline melting temperature(~348K) of EVA phase. Further the variation of conductivity during heating cooling cycle does not coincides and leads to some kind of thermal hysteresis due to change in conductive network structure. However in low temperature region (10-300K), the resistivity is found to increase with decrease in temperature (NCT effect) and hysteresis effect is also marginal compared to that observed in high temperature region. This difference resistivity/conductivity vs temperature behavior in two different temperature zones suggests that different two mechanisms are operative in the system.

A comprehensive assessment on degradation of multi-walled carbon nanotube-reinforced EMA nanocomposites

Thermal degradation kinetics of MWNT-reinforced EMA-based nanocomposites having different methyl acrylate (MA) contents (by % mass) ranging from 9 to 30% have been monitored. Kissinger and Flynn–Wall–Ozawa methods for evaluating non-isothermal degradation of polymers have been examined. Overall, the thermal stabilities of the nanocomposites are the function of amount of MWNTs loading and their state of dispersion that depends on the MA content of respective EMAs. Composite samples exhibit higher activation energy (Ea) than the neat EMAs but the Eas of the composites diminish with increased MA contents of the matrices. TG-Mass spectrometry has been used to identify the volatile products resulting from thermal degradation of composites, and a promising mechanism has been proposed over different range of temperatures of degradation. It is proposed that the side-group scission of methoxycarbonyl group initiates thermal decomposition following combination of chain end and random chain scission reactions, ensuing pseudo second-order kinetics.

A Novel Approach to Recycle the Waste Plastics by Bitumen Modification for Paving Application

Recycling of waste plastics (WP) denotes an effectual method to dispose the post-consumer products for possible alternative way to obtain new materials with good properties. With this aim the influences of WP and maleic anhydride (MA) grafted WPs (MA-g-WP) were investigated as the bitumen modifiers for paving applications. Fourier transform infrared (FTIR) spectroscopy analysis established the effective grafting of MA with the waste plastic (WP). Polymer modified bitumen (PMB) binders were analyzed under scanning electron microscopy (SEM) and optical microscopy (OP) in an effort to characterize the bitumen/modifier interphase morphology. The conventional rheological tests such as penetration test, softening point, and ductility results indicate that the degree of polymer modifications are function of the nature of modifier, bitumen–modifier compatibility, and modifier concentration. It has also been confirmed that the morphology observed by SEM and optical microscopy revealed the compatibility between MA-g-WP and bitumen, and the storage stability of binder was improved significantly compared with WP modified bitumen (WPMB) binders. Consequently, the use of grafted modifier with polar site can be considered as a suitable alternation for modification of binder in pavement by expecting their chances for better performance during service.

Effect of Recycled EVA as Modifier on the Various Properties of Bituminous Binder for Road Application

Recycled ethylene vinyl acetate (REVA) modified bituminous binders can be used in pavement construction for improved durability and enhanced performance in resisting permanent deformation of bituminous layers. This paper reports the thermogravimetric studies conducted on REVA modified bitumen (REMB) binders. The activation energies were determined from thermogravimetric analysis (TGA) data using Kissinger method, which does not require knowledge of the reaction mechanism. The effect of different percentages of REVA addition, as modifier in neat bitumen on the rheological properties, surface energy and microstructure of the bitumen/ REVA blends has been investigated in this study, which ensured the successful modification of bitumen with REVA.

Preparation, Properties, and Processibility of Nanocomposites Based on Poly(ethylene-Co-Methyl Acrylate) and Multiwalled Carbon Nanotubes

In this chapter, the preparation, characterization, processibility, and properties of nanocomposites based on multiwall carbon nanotubes (MWNTs) and different commercial grades of poly(ethylene-co-methyl acrylate) (EMA) having a variable methyl acrylate (MA) content are covered. The results showed that melt blending after solution mixing offers a simple and effective means to fabricate EMA/MWNT nanocomposites. The mechanical electrical properties and thermal degradation characteristics of the nanocomposites improve with increase in wt% of MWNT loading. The states of dispersions of the unmodified MWNTs are found to be inferior with increasing MA content in the EMA matrix. Better dispersions of MWNTs in EMA matrix lead to increased crystallite size and increased temperature of crystallization. The capillary rheological parameters can be correlated with the developed morphology under steady shear conditions. The effects of MWNTs and MA content in EMA on thermal stability and degradation kinetics are also presented. The kinetic parameters of degradation can be correlated with the degree of conversion. A promising mechanism is proposed over a different range of temperatures of degradation. The significant improvements in the mechanical and electrical properties of the polymeric matrix are observed by the addition of commercially available functionalized (hydroxyl and carboxyl) MWNTs. However, the states of dispersion of the functionalized MWNTs are found to be inferior in EMA matrix having lower MA contents. The morphology and properties of EMA-/modified MWNT-based nanocomposites are also investigated by using the plasma exposed, γ-ray irradiated, and chemically modified MWNTs. The improvement of technical properties of the matrix has been found to be higher with the plasma-modified MWNTs among all. It is also found that the electrical conductivity and EMI shielding effectiveness depend heavily on the type of functional groups present on the surface of MWNTs and also on MA content in EMA. These EMA/MWNT nanocomposites have potential applications especially, as a semiconductive layer in nuclear power plant cables, as an EMI shielding materials or as reinforced functional materials.

Effect of Hybrid Fillers on the Non-Linear Viscoelasticity of Rubber Composites and Nanocomposites

The present chapter focuses on the effect of hybrid fillers on the non-linear viscoelastic behaviour of rubber composites and nanocomposites. The viscoelastic behaviour of rubber composites include different properties like cure behavior, rheology, creep, and dynamic mechanical analysis etc. The properties measured under dynamic mechanical analysis are storage and loss moduli and tan δ. The variation of storage and loss moduli of rubber composites filled with different types of filler are discussed in detail. The non-linear viscoelastic behaviour (Payne effect) of rubber composites containing single filler are also discussed. The effect of various hybrid fillers on rubber composites are also discussed in detail and found composites containing hybrid fillers give better mechanical and viscoelastic properties than composites containing single filler. Composites containing hybrid fillers carry the properties of individual fillers. So composites of hybrid fillers are getting importance because they offer a range of properties that cannot be achieved with a single filler. Rubber composites containing hybrid fillers are promising class of materials with emerging applications in different fields like materials science, nanotechnology, and nanobiotechnology etc.