Adhesive Properties of Siloxane Modified Polyimides and Application for Multi-Layer Printed Circuit Boards

The adhesive properties of various siloxane modified polyimides were studied for the development of suitable adhesive materials with good thermal stability. Their adhesive properties were influenced by siloxane content in the polymer backbone and the structure of the aromatic component. Among them, the copolyimides with small amounts of the siloxane unit showed the better lap shear strength compared with the corresponding all-aromatic polyimides. They had excellent adhesive strength to various substrates. Their adhesive durability under the highly humid condition (25°C, 90%RH) was also improved mainly due to their lower moisture sorption and lower moisture permeability. However, further siloxane modification lowered their adhesive strength and durability. On the other hand, thee T-peel strength of copolyimides was lowered according to the increase of siloxane content. Based on this study, a new type of adhesive film which was composed of a copolyimide as a major component, SPB-505A, was developed and reported. This is useful for multi-layered printed circuit boards due to the excellent adhesive properties, good electrical properties and distinguished reliability under the hot / wet condition (121°C, 2 atm, 85%RH).     

Mechanistic Differences Between Kraft and Soda/AQ Pulping. Part 1: Results from Wood Chips and Pulps

Abstract

Soda pulping catalyzed by anthraquinone (AQ) or 2-methylanthraquinone (MAQ) can produce hardwood chemical pulps similar to kraft pulps in all respect but for bleachability. Results accumulated in our laboratory suggest that the residual lignin in pulps from anthraquinone catalyzed processes is less reactive toward bleaching chemicals than that in kraft pulps. Analyses of pulps by periodate and permanganate oxidations suggest that the residual lignin from the non-sulfur processes contained more condensed structures than kraft residual lignin. The low reactivity of these structures is believed to be responsible for the lower brightness of bleached soda-AQ (SAQ) pulps. Pulping and bleaching trials with hardwood chips demonstrated that shortening of the cooking time and/or increasing the alkalinity is one strategy for improving bleachability of SAQ pulps. When sugar maple (Acer saccharum) chips were SAQ cooked for 1.0 and 2.0 h at 165°C, the higher kappa number pulp produced after 1.0 h of cooking bleached to a significantly higher brightness with a small increase in the chlorine dioxide application.     

Morphological architecture of poly(p-oxybenzoyl) by modification of oligomer end-group

Influence of oligomer end-group on morphology of poly(4-oxybenzoyl) (POB) was examined by polymerizations of 4-acyloxybenzoic acids having different acyl groups. Polymerizations of 4-propionyloxybenzoic acid, 4-hexanoyloxybenzoic acid, 4-octanoyloxybenzoic acid and 4-decanoyloxybenzoic acid in liquid paraffin at 320 °C yielded needle-like or pillar-like POB crystals via crystallization of oligomers. On the other hand, the polymerization of 4-perfluorooctanoyloxybenzoic acid (FOBA) afforded microspheres having needle-like crystals on the surfaces. At an initial stage in the polymerization, microspheres having smooth surface were formed via liquid-liquid phase separation of oligomers prepared from FOBA owing to the low miscibility of perfluorooctanoyl end-group. Thereby the phase-separation behaviour of oligomers changed from liquid-liquid phase separation to crystallization at a middle stage in the polymerization and then needle-like crystals were formed on the surface of the microspheres. Chemical structure of the oligomer end-group affected significantly the phase-separation behaviour of oligomers and ultimately the morphology of POB.     

Thermal Expansion and Athermal Phase Transition of Y4AI2O9 Ceramics

Thermal expansion of Y₄A1₄O₉ ceramics prepared at 1600° and 1800°C was measured from room temperature to 1500°C in air. Volume changes at the phase transition of Y₄A1₂O₉, along with thermal hysteresis, were observed around 1400°C. The volume of the high-temperature phase was about 0.5% lower than that of the low-temperature phase. The hysteresis width for the sample prepared at 1600°C was 56°C, wider than that (14°C) for the sample prepared at 1800°C. The averages of phase transition start temperatures on heating and on cooling for these samples were, however, almost the same at 1377°C. The phase transitions did not occur at fixed temperatures, and the proportions of the high-temperature phase and the low-temperature phase did not change with time as long as the temperature remained constant ( athermal character). The sample prepared at 1800°C also showed another thermal hysteresis behavior from room temperature to about 1000°C.     

Phase Transition of Rare-Earth Aluminates (RE4Al2O9) and Rare-Earth Gallates (RE4Ga2O9)

Lattice parameters of RE₄Al₂O₉ (RE = Y, Sin, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb) prepared at 1600–1800°C and those of RE₄Ga₂O₉ (RE = La, Pr, Nd, Sm, Eu, and Gd) prepared at 1400–1600°C were refined by Rietveld analysis for the X-ray powder diffraction patterns. The parameters increased linearly with the ionic radius of the trivalent rare-earth elements ( r _RE). High-temperature differential calorimetry and dilatometry revealed that both RE₄Al₂O, and RE₄Ga₂O, have reversible phase transitions with volume shrinkages of 0.5–0.7% on heating and thermal hystereses. The transition temperatures (7_tr) decreased from 1300°C (Yb) to 1044°C (Sm) for RE₄A1₂O₉, except for Y₄Al₂O₉ ( T_tr = 1377°C), and from 1417°C (Gd) to 1271°C (La) for RE₄Ga₂O, with increasing ionic radius of the rare-earth elements. These transition temperatures were plotted on a curve against the ionic radius ratio of Al³⁺ or Gd³⁺ and RE³⁺ ( r _A1Ga/r_RE) except for Y₄Al₂O₉.     

Extracellular secretion of Escherichia coli alkaline phosphatase with a C-terminal tag by type I secretion system: purification and biochemical characterization

Type I secretion system (TISS) of Gram-negative bacteria permits proteins to be secreted directly from the cytoplasm to the external medium by a single, energy-coupled step. To examine whether this system can be used as an extracellular production system of recombinant proteins, Escherichia coli alkaline phosphatase (AP) was fused to a C-terminal region of Pseudomonas sp. MIS38 lipase (PML) and examined for secretion using the E.coli cells carrying the heterologous TISS. PML is one of the passenger proteins of TISS and contains 12 repetitive sequences and a secretion signal at the C-terminal region. The fusion protein was efficiently secreted to the extracellular medium, while AP was not secreted at all, indicating that the secretion of AP is promoted by a secretion signal of PML. The repetitive sequences were not so important for secretion of the fusion protein, because the secretion level of the fusion protein containing entire repeats ( approximately 10 mg/l culture) was only 2-fold higher than that of the fusion protein without repeats. The fusion protein purified from the culture supernatant existed as a homodimer, like AP, and was indistinguishable from AP in enzymatic properties and stability.     

Phase Equilibria and Ternary Intermetallic Compound with L1<Subscript>2</Subscript> Structure in Co-W-Ga System

Phase equilibria and stabilities of intermetallic phases appearing in the Co-rich portion of the Co-W-Ga ternary alloys were investigated and isothermal section diagrams at 1200, 1100, 1000, and 900 °C were determined. A fine cuboidal phase with an L1₂ structure was observed at 900 and 800 °C, where the composition of the new ternary compound obtained by aging at 900 °C for the Co-7.4W-12.0Ga alloy was Co-11.2W-11.4Ga (at.%). It was confirmed that this compound is metastable at 900 °C but is more stable at 800 °C. These results mean that the thermodynamic stability of the metastable Co₃W L1₂ phase, especially in the low temperature region, increases by the addition of Ga.