As an extension of our continuing studies concerned with the elucidation of three-dimensional network formation mechanism in the radical polymerization of multivinyl compounds, this paper deals with the post-polymerization of the precopolymers having pendant allyl groups prepared from the copolymerization of allyl methacrylate (AMA) with methyl methacrylate (MMA) or benzyl methacrylate (BzMA) as the model of prepolymer. Thus we obtained the following results : A remarkable concentration dependence was observed for the post-polymerization of poly (MMA-co-AMA) (P_w= 2600) as a high-molecular-weight precopolymer, whereas for the low-molecular-weight poly (MMA-co-AMA) (P_w= 100) was almost no concentration effect. Moreover, for the post-polymerization of poly (BzMA-co-AMA) (P_w= 3400) the concentration effect was quite reduced compared with poly (MMA-co-AMA). These results are discussed as correlated to the physical interaction among polymer chains.

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Vinylester resin having hydroxymethyl group (VEDA) was synthesized by the reaction of epoxy resin having hydroxymethyl group with acrylic acid. Effect of hydroxymethyl group on properties of cured resin was studied. VEDA was mixed with commercial vinylester resin in various ratios. The mixed vinylester resin was cured with dicumyl peroxide (DCP) as a catalyst. Glass transition temperature (Tg) of cured vinylester resin increased with increasing concentration of VEDA. This result was considered to be due to the increase of crosslinking density of the cured resin by condensation reaction of hydroxymethyl group. Tensile shear strength of adhesive was improved by the addition of VEDA to a commercial vinylester resin. This result was considered to be due to improve adhesion strength between cured resin and steel surface by introducing hydroxymethyl group. Next, urethane-modified vinylester resin was synthesized by the reaction of VEDA with isocyanate prepolymer. Tensile shear strength of adhesive was improved by introducing hydroxymethyl group and urethane linkage, and Tg of urethane-modified vinylester resin was nearly the same as that of unmodified resin.

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p-Cresol resin with only methylene linkage (PCR-0) was prepared by the condensation of p-cresol with paraformaldehyde in acetic acid, using HCl as catalyst. p-Cresol resins with dimethylene ether linkage (PCR-30, PCR-50, and PCR-80 : the number is the dimethylene ether linkage content in mol-%) were prepared by the condensation of monomethylol p-cresol and dimethylol p-cresol under N₂ and reduced pressure at 130-150°C. The solution properties of the p-cresol and acetylated p-cresol (Ac-PCR-0, Ac-PCR-50, and Ac-PCR-80) resins were determined by solution viscosity and solvation number in THF and CHCl₃. The molecular conformation of PCR-0 was compact in both THF and CHCl₃. However, the conformation of PCR-30, PCR-50, and PCR-80 more expanded as the fraction of dimethylene ether linkage in-creased. This trend was more remarkable in CHCl₃ than in THF. On the other hand, the conformation of Ac-PCR-0, Ac-PCR-50, and Ac-PCR-80 expanded in both THF and CHCl₃, independent of the fraction of dimethylene ether linkage. The strength of the hydrogen bond between phenolic hydroxyl groups in p-cresol resins was determined by IR spectroscopy. The strength in both THF and CHCl₃ was decreasing with increasing the fraction of dimethylene ether linkage. This trend was more remarkable in CHCl₃. This suggested that the hydrogen bond was formed between neighboring phenolic hydroxyl groups in the chain and the strength was weaker as the distance between neighboring phenolic hydroxyl groups was longer by introducing dimethylene ether linkage. Therefore, it was considered that the conformation of p-cresol resins was affected strongly by the intramolecular hydrogen bonds. The unperturbed dimension of Ac-PCR-50 was determined and it was larger than those of high-ortho novolak and acetylated o-cresol resin. It was found that the chain with dimethylene ether linkage expanded due to the weakness of intramolecular hydrogen bond and also to the nature of the skeleton of dimethylene ether linkage.

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The purpose of this investigation is to improve the toughness, water-proof, and electrical insulation of phenolic resin. For this purpose, distance between two crosslinking nodes of phenolic resin was made longer and density of phenolic OH group was made lower. In the concrete, glutaraldehyde was used instead of formaldehyde. At first, reaction condition such as the kind of solvent or catalyst was investigated in order to synthesize novolac type phenol-glutaraldehyde resin. As a result, the reaction was easily proceeded when acetic acid and HCI were used as solvent and catalysis respectively. Next, flowability and curing behavior of molding compounds which were prepared from phenol novolac, the phenol-glutaraldehyde resin, hexamethylenetetramine as curing agent, and wood flour as filler were investigated. As a result, when the content of the phenol-glutaraldehyde resin was less than 60wt%, the molding compounds were suitable for transfer molding. Curing rate was not depended on the content of the phenol-glutaraldehyde resin. Properties of cured resin by transfer molding from the molding compounds were also investigated. It was found that toughness, water-proof, and electrical insulation were improved by an increase of the content of phenol-glutaraldehyde resin.

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Synthesis and crosslinking of a self-crosslinkable copolymer having hemiacetal ester and epoxy moieties were designed. The radical copolymerization of 1-butoxyethyl methacrylate having hemiacetal ester moiety with glycidyl methacrylate-butyl methacrylate was carried out at 80°C for 6.5h using AIBN as an initiator to obtain the corresponding copolymer having the hemiacetal ester and epoxy moieties in the side chains. The obtained copolymer undertook the self-crosslinking through two-step reactions consisting of thermal dissociation of the hemiacetal ester moiety and esterification of the generated carboxyl with the epoxy groups. The curing rate increased as the temperature raised and the crosslinking reactions were completed at 160°C for 60min. The copolymer in xylene was stable under 50°C.

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Electron beam curable coatings were investigated to provide good film surface properties. These coatings based on the blend of two acrylate compounds were used in this work. One is the composition (A) consisting of polyurethane diacrylate and multi-functional urethane acrylate. Another is the composition (B) consisting of polyurethane diacrylate and multi-functional ester acrylate. Stain resistance was evaluated on the surface and the reverse of a coated film which was applied on a substrate such as a glass plate. The composition (A) gives good resistance to the reverse side. On the other hand, the composition (B) gives good resistance to the surface side. Based on the surface analysis, it results in good stain resistance that the multi-functional component is localized in the surface portion. Stain resistance was influenced by the composition of coatings, curing conditions and kinds of substrate.

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Recent investigations in the field of polymer science become more complicated and need a long term for completion. It is increasingly necceary year by year to use computer aided technologies for performing the investigations effectively on thermoplastics. There are introduced polymer-property predicting methods, such as molecular dynamics, statistics, and neural networks. On thermosettings, however, reports on the property prediction have never been published due to lack of data. The methods above mentioned can be applied to thermosetting plastics, too. Applications of generic code mechanism to those methods are made easier by using computer software.

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