Influence of the nigrosine dye on the thermal behavior of polyamide 66

To reveal the effect of the nigrosine dye, that the addition of the dye lowers the crystallization point (T_c) of molten polyamide resins with substantially no shift in the melting point (T_m), thus suppressing the crystallization enhancement of the crystalline nucleation agents, the characteristics of polyamide 66 (PA‐66) containing nigrosine dye EX (N‐EX) were investigated. Differential scanning calorimetry (DSC) analysis showed that the addition of N‐EX reduced the crystallization rate and T_c of molten PA‐66 with substantially no shift in T_m, and the crystallization enthalpy per unit of weight of PA‐66 was substantially constant. T_c of molten PA‐66 was lowered with an increase in the amount of N‐EX and reached its maximum at 13 wt % N‐EX. Dynamic mechanical analysis showed that the glass‐transition temperature and the secondary glass‐transition temperature increased with an increasing amount of the dye. On the other hand, the DSC and X‐ray diffraction results indicated that no dye molecule was present in the crystal structure of PA‐66. This effect of the nigrosine dye on PA‐66 is in contrast to those of crystalline nucleation agents, plasticizers, and antiplasticizers. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3270–3274, 2006     

Granulation of a hardmetal powder for spark plasma sintering

A fluidized bed granulation method, pressure swing granulation (PSG), was applied to granulation of a hardmetal powder without pressing lubricants for making the upstream process of spark plasma sintering (SPS) more efficient.

The properties of the granules were examined and compared with those of spray dried granules and extruded ones under the present system using a sieve.

Spherical granules between 0.15 and 0.84 mm in diameter difficult to obtain by the spray drying were obtained with high yield. The flowability of the granules was far better than that of spray dried granules and similar to that of extruded ones. Iron contamination and oxidization during pressure swing granulation were tolerable to the real production.     

Enhanced strain hardening in elongational viscosity for HDPE/crosslinked HDPE blend. I. Characteristics of crosslinked HDPE

Blending a crosslinked high‐density polyethylene (xHDPE) enhances melt strength and strain hardening behavior in elongational viscosity of high‐density polyethylene (HDPE) to a great degree. Gel fraction of xHDPE has a stronger effect on the strain hardening than sol fraction, although sol fraction also enhances the strain hardening to some degree. Further, the xHDPE crosslinked by peroxide in a compression mold exhibits more pronounced effect than xHDPE by radiation, which is attributed to the difference in the amount of the gel fraction. The xHDPE, which enhances the strain hardening, has sparse crosslink points in the network. Moreover, it was found from linear viscoelastic measurements, such as oscillatory modulus and relaxation modulus, that the xHDPE is characterized as a critical gel, which was also supported by the result of tensile testing. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 73–78, 2002     

Local disturbances preceding a running crack front in a viscoelastic solid

The local disturbances ahead of a running crack front in a viscoelastic solid were measured through noncontact electro-optical tools. It was observed that the very high local strain rate up to 200/sec exists even in the present quasistatic loading case. It may be concluded that the running crack propagation velocities, not the conventional average strain rates ranging from about 10^?4/sec to 10^?2/sec, govern the local disturbances, as the crack propagation velocities always exceed 200m/sec for both average strain rates, while the local strain rates observed do not show much differences between both average strain rate cases.     

Aggregation arrestant pheromone of the German cockroach,Blattella germanica (L.) (Dictyoptera: Blattellidae): Isolation and structure elucidation of blattellastanoside-A and -B

The aggregation pheromone of the German cockroach,Blattella germanica, consists of attractant and arrestant, which can be detected by olfactometer and choice-chamber assay, respectively. Both were extracted from the frass-contaminated filter paper being used as a shelter. They were separated by solvent partition withn-butanol and water. The arrestant from then-butanol phase was purified by open column chromatography and then successive HPLC isolated two major arrestant components. Spectral evidence from SI-MS, HR-EI-MS, and NMR experiments with pulse techniques provided possible structures as 1-(6-chloro-4,5-epoxy-5-stigmast-3-yl)--d-glucopyranoside and 1-(6-chloro-5-hydroxy-5-stigmast-3-yl)--d-glu-copyranoside, denoted as blattellastanoside-A and blattellastanoside-B, respectively. They represented arrestant activity as median effective doses (ED₅₀) at 0.044 (A) and 3.2 (B) nmol on 1.0 cm² of Whatman No. 1 filter paper.     

Optical Properties of Dysprosium-Doped Low-Phonon-Energy Glasses for a Potential 1.3 μm Optical Amplifier

Dysprosium-doped glasses were prepared in the system of gallium-based sulfide, tellurite, zirconium-baed and indium-based fluorides and their optical properties were studied. From the absorption cross sections of five f-f bands, three Judd-Ofelt parameters, ω _t ( t = 2, 4, 6), of Dy³⁺ ion were determined. The compositional variaton of the ω₂value showed the order sulfide > tellurite > fluorozirconate > fluoroindate, whereas the ω₆ value showed the opposite tendency. Compositional variaton of the fluorescence intensity ratio of the (⁴F_9/2⁶H_13/2)/(⁴F_9/2)→⁶H_15/2) is explained by the ratio of ω₂/ω₆ of doped Dy³⁺. The emission probabilities A and the branching ratio β from ⁶H_9/2 and ⁶F_11/2 levels, which are the doublet initial level of the 1.3 μm luminescence, were calculated for the glasses, and it was found that both values showed a tendency similar to that of ω₂ against the glass composition. In the sulfide glass, A was 2.6 × 10³S^-1 and β was 93%, both the highest in all of the glasses investigated. By 1.06 μm pumping of a Nd: YAG laser, the sulfide glass showed strong 1.3 μm emission and the lifetime was 25 μs, resulting in a quantum efficiency of 7%. This value is higher than that of the Pr³⁺:¹G₄ level in ZBLAN glass with β= 60%.     

Formation of Sm2+ lons in Sol-Gel-Derived Glasses of the System Na2 O-Al2O3-SiO2

Samarium ions (Sm²⁺) incorporated into aluminosilicate glasses by a sol-gel process showed persistent spectral hole burning at room temperature. Gels of the system Na₂O-Al₂O₃SiO₂ synthesized by the hydrolysis of Si(OC₂H₅)₄, Al(OC₄H₉)₃, CH₃ COONa, and SmCl₃·6H₂O were heated in air at 500°C, then reacted with H₂ gas to form Sm²⁺ ions. Whereas Al³⁺ ions effectively dispersed the Sm³⁺ ions in the glass structure, Na⁺ ions were not effective. The Al₂O₃-SiO₂ glasses proved appropriate for reacting the Sm³⁺ ions with H₂ gas and exhibited the intense photoluminescence of Sm²⁺ ions. The reaction of Sm³⁺ ions with H₂ in the Al₂O₂-SiO₂ glasses was determined by first-order kinetics, and the activation energy equaled 95 kJ/mol. At 800°C, the maximum photoluminescence of the Sm²⁺ ions was achieved within 20 min.     

Effect of molecular weight on molecular orientation and morphology of polypropylene sheets containing a β-nucleating agent

In this study, polypropylene (PP) films containing the β nucleating agent, N,N′-dicyclohexyl-2,6-naphthalenedicarboxamide, were prepared using PP with three different molecular weights (low, medium, and high) by extrusion process with T-shaped die. The structure and morphology of the films were studied after stretching. It was found that a unique molecular orientation, in which both the c-axis and crystalline lamellae were oriented perpendicular to the flow direction, was formed in all undrawn film samples, irrespective of the molecular weights of the PP. In the PP sheets stretched in the machine direction, the low-molecular-weight sample containing the nucleating agent exhibited brittle properties owing to a lack of tie chains in the stretching direction. In contrast, cavitation was prominent in the medium (M-PP)- and high (H-PP)-molecular-weight samples. Notably, M-PP containing the nucleating agent, with a high degree of molecular orientation, promoted the formation of a large number of voids. In H-PP containing the nucleating agent, the presence of numerous tie chains inhibited cavitation, resulting in fewer voids. The experimental results demonstrated the influence of the molecular weight on the void structure, which will be useful in the field of microporous membranes.     

Development of new-concept desk top size machine tool

A desktop multiprocess machinery has been designed that has two concepts: miniaturizing of machine tool and multiprocessing with a same machine tool. The prototype of desktop multiprocess machinery is developed in this study. This is tabletop size machine tool that has five changeable machining heads. Outline of main body and machining head are presented.In order to know the basic accuracy of desktop multiprocess machinery, experimental evaluation is carried out. Machining head setting error, stiffness of multiprocess machinery and straightness of X, Y, Z stage is measured. To study the basic performance of desktop multiprocess machinery, a complex machining experiment is carried out with the developed machine tool. The complex machining consists of three steps: electrode machining by milling, hole shaping by EDM, and hole finishing by ECM. These steps are performed in sequence on the same machine tool. The complex machining is successfully carried out. In order to evaluate the desktop multiprocess machinery from environmental point of view, machining energy, volume of machining liquid, and installation space of desktop multiprocess machinery are measured. The measured values are compared with estimated values with conventional machine tools. The machining energy, the volume of machining liquid, and the installation space of desktop multiprocess machinery are smaller than those of conventional machine tool.     

Crack initiation model for sensitized 304 stainless steel in high temperature water

To investigate the initiation behavior of stress corrosion cracking (SCC) for sensitized Type 304 stainless steel in high temperature water, a constant load SCC test method combined with in situ crack observation technique was employed. The in situ crack observation system allowed us to detect small cracks of at least 100 μm. As a result, a fracture time decreased with an increase in an applied stress. The first cracks were observed at most 3 h before the specimen was fractured under all the stress conditions. After that, many cracks were initiated in a short time to fracture. The fracture was caused by coalescence of multiple cracks rather than by growth of some primary cracks. The simulation model for surface crack initiation was newly developed using a Monte Carlo method, which was based on damage mechanics and stress analysis around the existing cracks. The simulation could represent the empirical results of changes in the crack distribution and the cumulative number of cracks during the SCC tests. It was concluded, therefore, that the crack initiation process should be considered in simulating the life prediction of the material in this SCC system.