Polybutylene terephthalate/high-density polyethylene alloys. I. Morphological studies

Polybutylene terephthalate (PBT) is a commercially successful thermoplastic polyester but has certain drawbacks such as low impact strength and low melt strength. An attempt has been made to modify the properties of PBT by blending it with polyolefin such as highdensity polyethylene (HDPE). Since PBT and HDPE are incompatible, an ionomer has been used as a compatibilizer to form an alloy. Alloys of PBT and HDPE with varying amounts (2-8%) of ionomer were prepared by melt blending. The ultimate mechanical properties improved significantly on the addition of the ionomer due to an increase in interfacial adhesion between PBT and HDPE. DSC studies show that the presence of ionomer facilitated the crystallization of PBT in the alloy. DMTA studies show that more of PBT (amorphous) is going in to the HDPE-rich phase in the presence of ionomer. The morphology of the alloys was studied using scanning electron microscopy (SEM), polarizing microscopy (PM), and small-angle light scattering (SALS). They showed improved dispersion of HDPE domains in PBT matrix with increasing ionomer content and change in the type of superstructure on adding the ionomer. It has been shown that an alloy of PBT and HDPE with improved mechanical properties and homogeneous morphology can be made with use of ionomer as a compatibilizer. Such alloys are cost effective and can find use in several engineering applications.     

Influence of untreated and novel electron‐beam‐modified surface‐coated silica filler on the thermorheological properties of ethylene–octene copolymer

We developed surface‐modified silica fillers by coating these with an acrylate monomer, trimethylolpropane triacrylate, or a silane coupling agent, triethoxyvinyl silane, followed by electron‐beam irradiation at room temperature. These were incorporated in an ethylene–octene copolymer rubber. Thermorheological studies of the unvulcanized ethylene–octene copolymer and its untreated and modified silica‐filled composites were done with a shear dynamic oscillating rheometer. Modification of the silica filler, especially via the silanization process followed by electron beam treatment, significantly reduced filler–filler networking as revealed from the log–log plots of storage modulus and complex shear viscosity, and its real component. The rheological complexity of the compositions was analyzed from a double logarithmic plot of the storage modulus and loss modulus. The results obtained from the master curves constructed on the basis of the time–temperature superposition principle and the activation energy calculated from the Arrhenius equation for the flow of above these compounds further supported these findings. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2453–2459, 2003     

Viscometric studies of starch-g-polyacrylamide composites

Composites of starch-g-polyacrylamide, starch, and polyacrylamide have been prepared by gamma radiation-initiated polymerization of acrylamide in the presence of starch in aqueous medium. The polymerization was studied as a function of the (i) amount of water (ii) monomer concentration, and (iii) total dose. The optimum conditions for maximum conversion of the monomer to homopolymer and graft copolymer have been evaluated. Percentage of grafting of polyacrylamide could not be determined precisely as both the homopolymer and the graft are soluble in common solvents and all attempts to separate the graft from the homopolymer were unsuccessful. However, the formation of the starch-g-polyacrylamide copolymer was confirmed by the turbidimetric studies using acetone as a nonsolvent. The products of polymerization of acrylamide in the presence of starch consisted of unreacted starch, starch-g-polyacrylamide, and polyacrylamide and is referred to as the composite. Acrylamide was also polymerized in the absence of starch using γ-rays as means of initiation and the optimum conditions for maximum conversion of acrylamide to polyacrylamide have been evaluated. Viscosity behavior of the composite and polyacrylamide was studied in aqueous medium at 30±0.04°C. The reduced specific viscosity of the aqueous solution of acrylamide and the composite as well was found to increase with increasing dilution, the effect being more pronounced in the composite. This tends to indicate that both the homopolymer and the composite behave as polyelectrolytes. An attempt has been made to explain the polyelectrolytic behavior of the homopolymer and the composite. © 1993 John Wiley & Sons, Inc.     

Ion-solvent interaction from viscosity and apparent molar volume of bromates,iodates and sulphates of potassium and sodium in dioxane-water mixtures at different temperatures

The viscosity and apparent molar volume of solutions of KBrO₃, NaBrO₃ KIO₃, NaIO₃, K₂SO₄ and Na₂SO₄ in dioxane (mass fraction: 10, 20 and 30%)-water mixtures at 30, 35, 40 and 45°C have been measured. The ions appear to interact appreciably and the ion-solvent interaction is of the order BrO^?₃ > IO^?₃ > SO^2?₄ and K⁺ > Na⁺.     

Interfacial layer quality effects on low-frequency noise (1/f) in p-MOSFETs with advanced gate stacks

The effects of interfacial layer quality on the low-frequency noise behavior of p-channel MOSFETs with high-κ gate dielectric and metal gate are investigated. Devices with chemically grown SiO₂ interfacial layers (0.8 nm) are compared with N₂O (0.8 nm) interfacial oxides. A 0.4 nm SiO₂ interfacial layer device is used for comparison purposes. A cross-over kind of behavior has been observed in N₂O devices, which occur at lower gate voltages (1.2–1.3 V) when normalized spectral densities and input referred noise are investigated. This behavior is found to be closely related to the observed transconductance variation in these devices. The dominant mechanism of 1/f noise is found to be Hooge’s mobility fluctuations. Hooge’s parameter, as a figure of merit, shows an increase for 0.4 nm devices when compared to 0.8 nm devices, while 0.8 nm N₂O devices confirm their cross-over nature.     

Multilayer Hierarchical Model for Mobility Management in IPv6: A Mathematical Exploration

The mobility solution provided by Mobile IPv6 (MIPv6) imposes too much signaling load to the network and enforces large handoff latency to end user. Hierarchical MIPv6 (HMIPv6) on the other hand, is designed by organizing MIPv6 in layered architecture and performs better than MIPv6 in terms of handoff latency and signaling load. Observation shows that, there is still possibility to shrink the handoff latency and the signaling load by further extending HMIPv6 into multiple layers. To explore this possibility of enhanced performance through layered architecture, this paper aimed at mathematical exploration of an N-layered MIPv6 network architecture in order to figure out the optimal levels of hierarchy for mobility management. A widespread analysis is carried out on various parameters such as location update frequency and cost, handoff latency and packet delivery cost. Influence of queuing delay on handoff latency is examined by modeling M/M/1/K queue in the architecture and user mobility is modeled using Markov chain. Analytical investigation reveals that three levels of hierarchy in MIPv6 architecture provide an optimal solution for mobility management.     

Failure mechanisms of pure silver, pure aluminum and silver–aluminum alloy under high current stress

This study investigates the suitability of pure silver (Ag), pure aluminum (Al) and silver (3 at.%-aluminum) alloy (Ag(Al)) metallizations for potential application in programmable fuse links in field-programmable gate arrays. Single-line test-structures of the metallizations, of varying line widths (2.5–10 μm) on titanium nitride (TiN) and SiO₂, have been investigated by subjecting them to extremely high current-density conditions. With increase in applied current densities, the lines experienced catastrophic failure. The microstructure and topography of the failed sites was examined using scanning electron microscopy and correlated with failure times. The failure mechanism for all three metallizations was dominated by Joule heating produced by the high currents flowing through the lines. For Ag and Ag(Al) structures on SiO₂, failure occurs by Joule-heating-induced vaporization of metallization. In the case of Ag and Al metallizations on TiN, failure is due to vaporization of metallization followed by mechanical cracking of the barrier thin film due to thermal stresses that act on the layers.