Formations and reactivities of emulsifier radicals were investigated by means of electron spin resonance (ESR) to understand the chemical role of emulsifiers in emulsion polymerization. Formations of the emulsifier radicals were initiated by generation of hydroxyl radicals from a redox couple of TiCl3 and of H202 and the following results were obtained. All the ESR spectra from emulsifiers containing hydrophylic oxyethylene chains were the same and assigned to the radical, -CH2OCHCH2OCH2-, formed by hydrogen abstraction from oxyethylene, even if their hydrophobic groups are different. PVA radical was assigned to -CH2CH(OH), which was formed by chain scission followed by hydrogen abstraction from secondary alcohol, -CH(OH)-. No signals were observed from gum Arabic or hexadecyl trimethyl ammonium bromide. Addition of vinyl monomers retarded the formation of emulsifier radicals. Reactivities of the radicals from polyoxyethylene nonylphenol ether were extensively studied and the rate constants, k3, k5 and the rate constant ratio, k5/k3, were estimated to be ～106, ～102 in l/mol・sec and ～10-4, respectively, where k3 is the rate constant for the termination reaction between the emulsifier radicals and k5 is the rate constant for addition of the emulsifier radical to VAc. This addition reaction is significant especially, since it is the first step to result in the block copolymer, PVAc-b-polyoxyethylene nonylphenol ether, which is expected to act as an excellent stabilizer in PVAc emulsion.

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We have investigated the effects of corrosive gases on corrosion and adhesion properties of the conductive pastes used for electronic device interconnection wires and electrodes. We examined three different polymer-type conductive pastes. All three pastes contain silver particles as their conductive filler. In one of the pastes, polyester is used as the binder; in another, silicone; and in the third, epoxy resin. We applied each conductive paste to a flexible bilayer polyimide printed-circuit board and then let them cured. We then subjected the cured conductive pastes to an acceleration test, placing the board in a tank filled with a mixture of corrosive gases. The test conditions we set up were equivalent to exposing a sample of silver to a typical Southeast Asian environment for five years, as follows: 2 ppm hydrogen sulfide gas, 4 ppm nitrogen dioxide gas, a temperature of 30℃, a relative humidity of 70%, and testing duration of 77.3 hours. To analyze the resulting corrosion, we cut samples, using the SAICAS slant-cut method, and checked the sulfur component in the cut section of each sample by using both the scanning electron microscope and the EDX component analysis method. We found that, for each of the pastes, the corrosion reached a depth of about 2μm, as expected. We also measured the adhesion properties of each conductive paste, using the SAICAS method. As a result, we haveconfirmed that the conductive paste which contains epoxy resin as its binder has a higher adhesion with respect to horizontal peeling than the other types, and that its adhesion does not deteriorate, even after the corrosion test.

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Organic-inorganic hybrid coatings were prepared by the sol-gel method using tetraethoxysilane (TEOS) with silane coupling agents: γ-methacryloxypropyltrimethoxysilane (MPTMS) and γ-methacryloxypropyldimethoxymethylsilane (MPDMS). To prepare polymers for the sol-gel process, polymerization of MPTMS or MPDMS and copolymerization of methyl methacrylate (MMA) with MPDMS were performed by radical reactions. Transparent, colorless, and crack-free coatings lμm in thickness were obtained on metal substrates (silver, copper, and aluminum) after heat treatment at 150℃ from sol solutions with TEOS/methacrylate molar ratios of 0.1-0.4. The coatings derived from polyMPTMS-TEOS sol and polyMPDMS-TEOS sol were insoluble in ethanol, acetone, and tetrahydrofuran, while the coating derived from poly(MMA-co-MPDMS)-TEOS sol was soluble in these solvents. The former coatings showed higher wear and heat resistance than the latter. Furthermore, we examined the effect of addition of γ-mercaptopropyltrimethoxysilane (MerPTMS) into the polyMPDMS-TEOS system on adhesion to the silver substrate by X-ray photoelectron spectroscopy (XPS).

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The composites were prepared by molding coconut fiber with either polylactic acid (PLA) or polybutylene succinate (PBS) in the cyclohexanone and characterized. Formulations of the composites (types of biodegradable polymer and ratios of fiber to polymer) were optimized. Physical and mechanical properties,including water content, microscopic examinations by CCD and SEM, apparent density, and mechanical properties of coconut fiber, polymers and composites were investigated. The incorporation of the PLA and PBS polymers to coconut fiber significantly improved the physical and mechanical properties of the composites. Both PLA and PBS polymers produced composites with similar appearances. Increasing polymer contents essentially increased the apparent density, flexural strength and modulus of elasticity, and all samples exhibited enhanced adhesive properties. However, increasing more polymer contents could adversely affect the composite preparation, particularly the difficulty of mixing and homogeneity. Generally, composites made from PLA had almost the same flexural strength at break and modulus of elasticity when compared to those of PBS composites at certain polymer concentrations. Nevertheless, thin film layers of some PBS composites may clearly be appeared if higher polymer contents were used, as examined by CCD. The composite with approximately 50% PLA and the coconut fiber of 50% has been satisfied our requirements of physical characteristics and mechanical properties.

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