Poly(L‐lactide). X. Enhanced surface hydrophilicity and chain‐scission mechanisms of poly(L‐lactide) film in enzymatic,alkaline, and phosphate‐buffered solutions

Attempts were carried out to enhance the surface hydrophilicity of poly(L ‐lactide), that is, poly(L ‐lactic acid) (PLLA) film, utilizing enzymatic, alkaline, and autocatalytic hydrolyses in a proteinase K/Tris–HCL buffered solution system (37°C), in a 0.01N NaOH solution (37°C), and in a phosphate‐buffered solution (100°C), respectively. Moreover, its chain‐scission mechanisms in these different media were studied. The advancing contact‐angle (θ_a) value of the amorphous‐made PLLA film decreased monotonically with the hydrolysis time from 100° to 75° and 80° without a significant molecular weight decrease, when enzymatic and alkaline hydrolyses were continued for 60 min and 8 h, respectively. In contrast, a negligible change in the θ_a value was observed for the PLLA films even after the autocatalytic hydrolysis was continured for 16 h, when their bulk M_n decreased from 1.2 × 10⁵ to 2.2 × 10⁴ g mol^?1 or the number of hydrophilic terminal groups per unit weight increased from 1.7 × 10^?5 to 9.1 × 10^?5 mol g^?1. These findings, together with the result of gravimetry, revealed that the enzymatic and alkaline hydrolyses are powerful enough to enhance the practical surface hydrophilicity of the PLLA films because of their surface‐erosion mechanisms and that its practical surface hydrophilicity is controllable by varying the hydrolysis time. Moreover, autocatalytic hydrolysis is inappropriate to enhance the surface hydrophilicity, because of its bulk‐erosion mechanism. Alkaline hydrolysis is the best to enhance the hydrophilicity of the PLLA films without hydrolysis of the film cores, while the enzymatic hydrolysis is appropriate and inappropriate to enhance the surface hydrophilicity of bulky and thin PLLA materials, respectively, because a significant weight loss occurs before saturation of θ_a value. The changes in the weight loss and θ_a values during hydrolysis showed that exo chain scission as well as endo chain scission occurs in the presence of proteinase K, while in the alkaline and phosphate‐buffered solutions, hydrolysis proceeds via endo chain scission. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1628–1633, 2003     

Highly Reactive β-Dicalcium Silicate: III, Hydration Behavior at 40–80°C

The effect of curing temperature (40°, 60°, 80°C) on the hydration behavior of β-dicalcium silicate (β-C₂S) was investigated. The β-C₂S was obtained by decomposition of hillebrandite, Ca₂(SiO₃)(OH)₂, at 600°C, has a specific surface area of about 7 m²/g, and is in the form of fibrous crystals. The dependence of the hydration reaction on temperature continues until the reaction is completed. The hydration is completed in 1 day at 80°C and in 14 days at 14°C. The hydration mechanism is different above and below 60°C, but at a given temperature, the reaction mechanism and the silicate anion structures of C-S-H do not change significantly from the initial to the late stages of the reaction. High curing temperature and long curing times after completion of reaction promote silicate polymerization. The Ca/Si ratio of C-S-H shows high values, being almost 2.0 above 60°C and 1.95 below 40°C.     

Computer-aided reaction system synthesis based on structured process energy-exergy-flow diagram

A computerized thermodynamics-oriented procedure for reaction system synthesis is proposed. First, hierarchy structure of chemical reactions is discussed and the reaction system is categorized into three types; (1) combination with a heat source or sink, (2) combination with a reaction donor, and (3) decomposition of target reaction into subtargets. Then, the algorithm to find subtarget reactions and/or donor reactions is presented.     

Measurement of zeolite,silicate, and phosphate in laundry detergent products by inductively coupled plasma atomic emission spectrometry

This paper reports the development of a method for simultaneously measuring zeolite, silicate, and phosphate in laundry detergent products by inductively coupled plasma atomic emission spectrometry. A sample is decomposed under alkaline oxidative conditions to decompose zeolite, silicate, phosphate, and organic substances. Then hydrochloric acid is added to the decomposed solution to dissolve aluminum hydroxide precipitate before analysis. This sample preparation procedure was investigated by using a total organic carbon analyzer and was confirmed to be applicable to simultaneous measurements of zeolite, silicate, and phosphate. Relative standard deviation for the analysis is less than 2.1%, recovery is more than 99.0%, and the calibration curve gives a correlation coefficient ofR=1.000. The detection limit of this method for aluminum and silicon is 0.1%, and for phosphorus, 0.2% by weight in the product. This method is applicable to various laundry detergent products that contain zeolite, silicate, or phosphate and is five times faster than the three wet chemical methods.     

Characterization of polyethylene/EPDM/silicon dioxide multicomponent composites by solid-state dynamic mechanical spectroscopy

Various composites of polyethylene, ethylene propylene diene rubber (EPDM), and filler are milled and analysed by solid-state dynamic mechanical spectroscopy. The filler used is silicon powder with an oxidized surface. This filler is a model for materials with siliceous surfaces. The torsion pendulum measurements show that the multicomponent composites exhibited complex viscoelastic behaviour. For composites of polyethylene and silicon dioxide, there is evidence of particle-particle interactions. In composites which include polyethylene, rubber and filler, interactions of the polyethylene and especially of the rubber with the filler surface are significant. Treatment of the filler surface with gamma-aminopropyltriethoxysilane (-APS) or gamma-methacryloxypropyltrimethoxysilane (-MPS) has a significant influence on the resultant composite dynamic mechanical spectrum. Maleic anhydride grafting of the EPDM rubber also changes the character of the composites. These composites appear to exhibit complex morphologies, which may be controlled to a certain extent by filler surface treatment and grafting to the rubber. There is evidence for a chemical reaction between the maleic anhydride modification of the EPDM and -APS during processing on the roll mill. Prediction of the composite properties using the extended van der Poel model is qualitatively useful.     

Pb-Free solders: Part 1. Wettability testing of Sn−Ag−Cu alloys with Bi additions

Maximum bubble pressure, dilatometric, and meniscographic methods were used in the investigations of the surface tension, density, wetting time, wetting force, contact angle, and interfacial tension of liquid alloys of Sn−Ag−Cu eutectic composition with various additions of Bi. Density and surface tension measurements were conducted in the temperature range 250–900 °C. Surface tensions at 250 °C measured under a protective atmosphere of Ar−H₂ were combined with data from meniscographic studies done under air or with a protective flux. The meniscographic data with a nonwetted teflon substrate provided data on interfacial tension (solder-flux), surface tension in air, and meniscographic data with a Cu substrate allowed determinations of wetting time, wetting force, and calculation of contact angle. The calculated wetting angles from meniscographic studies for binary Sn−Ag eutectic and two ternary Sn−Ag−Cu alloys were verified by separate measurements by the sessile drop method under a protective atmosphere with a Cu substrate. Additions of Bi to both ternary alloys improve the wettability and move the parameters somewhat closer to those of traditional Sn−Pb solders.     

Pb-Free solders: Part II. Application of ADAMIS database in modeling of Sn−Ag−Cu alloys with Bi additions

The ADAMIS database was used for calculation of the surface tension of the quaternary Sn−Ag−Cu−Bi liquid alloys by Butler's model. The resultant data were compared with those from the maximum bubble pressure measurements from Part I. The same thermodynamic database was next applied for the calculation of various phase equilibria. It was established that the Bi addition to the ternary Sn−Ag−Cu alloys (Sn-2.6Ag-0.46Cu and Sn-3.13Ag-0.74Cu in at.%; Sn-2.56Ag-0.26 Cu and Sn-2.86Ag-O.40Cu in mass%) causes lowering of the melting temperature and the surface tension to make the tested alloys closer to, traditional Sn−Pb solders. The simulation of the solidification by Scheil's model showed that the alloys with the higher Bi concentration are characterized by the lifting-off failure due to the segregation of Bi at the solder/substrate boundary. Thus, in modeling of new Pb-free solders, a compromise among various properties should be taken into consideration.     

Interpretation of reflection and transmission spectra for thin films: transmission

The optical behavior of a thin film, that is, peak positions and intensities, is discussed for transmission under a thin-film approximation. The infrared transmission spectra of thin films, both standing films and those on dielectric substrates, are simulated for s and p polarization at various angles of incidence. For spectral simulation, the matrix method is used in conjunction with noise-free complex refractive indices based on the dispersion theory. The peak positions in the simulated spectra are compared with transverse optic and longitudinal optic frequencies based on the macroscopic theory. The simulated peak intensities for the standing films are compared with the prediction based on the thin-film approximation. Furthermore, it is found from the spectral simulation for thin films on dielectric substrates that the peak intensity for a thin film may depend on the thickness and refractive index of the substrate.     

Gap symmetry and intrinsic intraplane pinning of untwinned YBa2Cu3O7 single crystals

The interplane (cb) and intraplane (ab) anisotropy of untwinned YBa₂ Cu₃0₇ single crystals has been investigated by means of the torque magnetometry. To extract the reversible and irreversible components, the torque was measured as a function of increasing angle as well as decreasing angle. The interplane irreversible torque _irr shows two-fold peaks at _c =90 ° and270 ° (of half width11 ° at77 K) due to the well-known intrinsic interplane pinning. A novel intrinsic pinning has been discovered in the intraplane irreversible torque, i.e., _irr shows four-fold peaks of half width20° at77 K when _a =0 °, 90 °, 180 ° and270 °. We argue that the intrinsic intraplane pinning comes from the four-fold nature of the gap parameter.     

A Hilbert warping method for handwriting gesture recognition

We propose a novel sequence alignment algorithm for recognizing handwriting gestures by a camera. In the proposed method, an input image sequence is aligned to the reference sequences by phase-synchronization of analytic signals which are transformed from original feature values. A cumulative distance is calculated simultaneously with the alignment process, and then used for the classification. A major benefit of this method is that over-fitting to sequences of incorrect categories is restricted. The proposed method exhibited higher recognition accuracy in handwriting gesture recognition, compared with the conventional dynamic time warping method which explores optimal alignment results for all categories.