In the reaction system of bisphenols, obtained from phenols and formaldehyde with homogeneous acid catalysts, a molecular weight controlling effect appeared through adding certain solvents for phase separation by controlling the transportation of reactants and catalysts.
In the phenol system having relatively high water solubility, no phase separation occurred through adding only water, and the higher the amount of water, the higher was the paraselectivity of bisphenol. By adding water with water-insoluble inert solvents such as toluene, there appeared phase separation and molecular weight controlling effect with high paraselectivity.
Using relatively low water soluble o-cresol, the phase separation and the same effect appeared through adding only water, but the best result was obtained by combining water with toluene. Thus the o-cresol system gave better results than the phenol one.
By investigating material ballance, most part of acid catalyst was recognized to be in water phase and of bisphenols in oil phase. This fact indicated that the further reactions from bisphenols to multinuclear compouds were limited and easily led to the phase separation phenomenon which gave a good molecular controlling effect.
Catalyst species with hydrophillic property, such as oxalic acid and hydrogen chloride generally gave a good result, and better was hydrogen chloride. Ones with somewhat lipophillic nature, such as p-toluenesulphonic acid and dodecylbenzenesulphonic acid gave no molecular weight controlling effect, even in the phase separation system.
In comparison with the homogeneous phase reactions, the phase separative reactions gave pure bisphenols which had higher para-selectivity and a lower content of multinuclear compounds at the same formaldenhyde/phenols molar ratio. Under the same content of multinuclear compounds, the phase separative reactions could achieve a 2-to 3-time higher value in molar ratio, thus giving a 2-to 3-time higher yield of bisphenols with high paraselectivity.

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Several kinds of epoxy resins having biphenyl structure were synthesized, and the relation between the strucrure and properties of their cured products with phenol novolac was studied.
The measurements of fracture toughness of the cured products showed that the epoxy resin prepared from 4, 4′-dihydroxybiphenyl exhibited higher fracture resistance than 2, 2'-isomer. 4, 4′-isomer gave small storage modulus below Tg in dynamic mechanical analysis and gave small specific gravity, depending on its increased free volume fraction caused by the prevention of packing of molecular chains in cured product of epoxy resin having a stiff backbone like 4, 4′-biphenyl structure. The increased toughness of 4, 4′-isomer seems due to the increase of plastic deformation at crack-tip because of its large free volume fraction.

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Naphthalene based epoxy resins were synthesized from dihydroxynaphthalenes, and the relation between the strucrure and properties of their cured products with phenol novolac was studied.
The measurements of fracture toughness of the cured products showed that the epoxy resin prepared from 2, 6-dihydroxynaphthalene had high fracture toughness of 1.2 MPa·m^1/2. 2, 6-isomer gave small storage modulus below Tg in dynamic mechanical analysis, which depends on the increase of free volume fraction caused by the restriction of packing of molecular chains under the influence of stiff backbone, i.e. 2, 6-naphthalene structure. The increased toughness of 2, 6-isomer seems due to the increase of plastic deformation at crack-tip because of its large free volume fraction.

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The dry prepreg and its lamination was studied using novel cycloaliphatic epoxy resins (CE-resins) derived from 2, 7-octadienol, since the CE-resins have mild reactivity with BF₃·MEA hardener and give good thermal and mechanical properties. The dry perpreg under the drying conditions at 100-120°C for 5-8 minutes using toluene-methylethyl ketone mixture, showed a good shelf life but too poor flowability to laminate.
Trial for improving the flowability by adding the conventional two-functional cycloaliphatic epoxy resins was effective in achieving a good lamination. Thus, the first cycloaliphatic epoxy laminate, obtained from dry prepreg under the press condition of 175°C and 105 kgf/cm2, proved to have characteristics such as good thermal and mechanical properties as well as good arc and tracking resistance, as expectedly.
The only defect of poor water resistance in the cured cycloaliphatic epoxy composites was improved by the selected surface treatment on the glass cloth for strong adhesion.

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Dry film photoresist (DFR) comprising solid thin layer of photoresist is widely used as the material of image transfer fabrication for manufacturing Printed Circuit Boards (PWBs). This paper discusses the properties of DFR required for producing a fine pattern and comments on new types of DFR introduced in recent years.

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Artificial marbles have become to use in residential housings, especially kitchens and bathrooms. Artificial marbles consist of thermosetting resins, such as unsaturated polyesters and acrylics, and inorganic fillers. They meet user's image because of good appearance, soft touch feeling, and high quality.
Now, there can be seen the change in the process from casting to press molding with heated metal molds for improving the efficiency. Accordingly, many resins are being developed so as to meet a recent trend.
This article describes recent progress and development on resins, molding methods, and requirements for attaining high performance products.

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Amino resins are representative thermosetting plastics like phenolic resins. They could be classified into urea resins and melamine resins. Main application of urea resins is adhesive agents and molding compounds, etc, while, melamine resin are the adhesive agent, paints, molding compounds, and lamination boards, etc.
This article highlighted the application of molding compound, and here we would like to report the recent market trend and technical development.

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