The KSCN complex of 5, 5'-carbonylbis [1, 3-dimethyl-3, 4, 5, 6-tetrahydro-1, 3, 5-triazin-2 (1H) -one] (CDTTO) (KSCN : CDTTO = 1 : 1) was prepared. The molecular structure of this complex was determined by means of X-ray analysis and compared with the molecular structure of the CuC1₂complex of CDTTO. A white transparent crystal with dimensions of ca. 0.2*0.2*0.3mm³ was mounted on a Rigaku AFC-6S automated diffractometer.
Crystal Data, C₁₁H₂₀N₆O₃·KSCN· H₂O, F.W.= 399.54, monoclinic, space group P2₁/c, a =11.745 (2), b = 23. 357 (7), c= 7. 010Å (2), β= 98.85 (2) °, V=1900. 3ų, Z = 4, Dc =1. 40g/cm³, μ (Mo Kα) =4.1cm^-1
The structure was solved by the direct method and refined anisotropically for Non-H atoms and isotropically for H atoms by a block-diagonal least-squares method. The final discrepancy factors were R = 0.066 and Rω= 0.068. The crytal has one mole of water of crystallization per mole of the complex.
The four atoms of C (1) O (1), N (1), and N (4) lie nearly on the same plane. The least-squares planes formed by the seven atoms of N (1) - (3), C (2) - (4), and O (2) and by the other seven atoms of N (4) - (6), C (5) -C (7), and O (3) intercept the former plane (the ureido moiety) at 97. 4 and 83.5°, respectively. The bond lengths for the carbonyl groups of C (1) -O (1), C (4) -O (2), and C (7) -O (3) are 1.212, 1.240, and 1. 230Å, respectively. While C (1) -O (1) has a strong double bond character, C (4) -O (2), and C (7) -O (3) are intermediate between single and double bonds. These carbonyl bonds are shorter than that of C (4) -O (2) in the CDTTO-CuC1₂ complex. This difference is due to the absence and presence of stabilization of the anionic structure of oxygen atoms by the absence (CDTTO-KSCN) and presence (CDTTO-CuC1₂) of the coordination to cation.
The distance between K⁺and NCS^-is 2.884Å and suggests a strong interaction. The distance between K⁺and oxygen or nitrogen atom in CDTTO molecule suggests no coordination of K⁺to these atoms. These results suggest that KSCN may be stabilized together with the water of crystallization in the cavities formed by the CDTTO molecules.

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Two types of chemical analysis were successfully applied to determine three functional groups in the epoxides cured with carboxylic acid.
The functional group in the cured epoxides is difficult to analize by the known methods because the cured epoxides are insoluble in organic solvents. Therefore, the cured epoxides should be pretreated by freeze milling and swelling with tetrahydrofuran. Two methods of chemical analysis with a potentiometric titration were proposed. The first one is the hydrochloric acid-tetrahydrofuran method, effective for simultaneous determination of the epoxide and carboxyl groups in the cured epoxides, and another is the acetyl bromide method, also effective for simultaneous determination of the epoxide and hydroxyl groups in the cured epoxides. The relative standard deviations were 2.6-4.4% for epoxide group, 2.5% for carboxyl group and 5.5% for hydroxyl group, respectively.
The determination of three functional groups in the cured epoxides by these methods have made possible to estimate a curing mechanism of epoxides with carboxylic acid.

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The definition of toughness is the first issue that must be clarified in describing toughness in thermoset resins. This review is focused on toughness as measured by resistance of a material to the propagation of cracks. First, toughness obtained by fracture toughness tests has been reviewed. Toughness under crack propagation condition is achieved in polymers by the involvement of a significant volume of material in the deformation zone. For maximum toughness, the crack tip deformation processs is shear yielding. The addition of dispersed rubber particles can enhance shear yielding due to local stress concentrations around the particle. The onset and development of shear yielding around the rubber particles have been discussed on the basis of FEM calculations.

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As a part of basic studies concerned with the modification of diallyl phthalate (DAP) resin, the curing reaction of DAP was investigated in detail in the presence of methacrylate-network. That is, the curing processes in various monomethacrylate-dimethacrylate-DAP systems were examined, in which monomethacrylate-dimethacrylate copolymer network is formed as a first network at an early stage of polymerization, reflecting of high polymerizability and low copolymerizability of methacrylate monomer toward DAP. Thereafter, the polymerization of DAP proceeds in the presence of the first network.
The tensile strength of the cured resin was first measured under various conditions ; the enhancement of strength was induced by the first network of moderate crosslinking density and of good compatibility with DAP polymer chain. This result was then discussed from the following standpoints, i. e. 1) the formation of first network in DAP and 2) the polymerization of DAP in the presence of the first network. Thus, the enhanced strength of cured resin can be attributed to a reduction of the size of the microgel produced in the curing process of DAP, as a consequence of restricted space of polymerization by first network.

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Aromatic poly (amide-imide) (PAI) was prepared by the heating of poly (amic acid-amide) (PAAA) obtained by the polycondensation of trimellitic anhydride chloride with 4, 4'-diaminodiphenylether or 4, 4'-diaminodiphenylmethane in mixed solvent of methyl ethyl ketone with water (MEK/H₂O) and in N, N-dimethylacetamide (DMAc). The effects of polymerization solvent and polymer structure on the curing of several PAIs were investigated and the following results were obtained.
(1) The carboxyl group content of PAIs from PAAAs prepared in MEK/H₂O was larger than those in DMAc. The carboxyl groups of PAIs were completely blocked by esterification with triethyl orthoacetate.
(2) The curing of PAIs prepared in MEK/H₂O proceeded easier than that in DMAc.
(3) The curing of PAIs was retarded by esterification of those carboxyl groups.
(4) PAIs having diphyenylmethane structure was easier cured than those having diphenylether structure in air.
Based on the above results, it was concluded that the curing of PAIs by heating was due to the crosslinking reaction between functional groups of PAI, such as carboxyl and amino groups. Furthermore, the oxidation of diphenylmethane structures of PAIs was considered to play important roles in the curing of PAIs in air.

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Solid-state CP/MAS (Cross Polarization/Magic Angle Spinning) -¹³C-NMR spectroscopy was applied to the analysis of the curing reaction of the blends of maleimide resin, which formed from bismaleimide and aromatic diamine, and epoxy resin.
In CP/MAS-¹³C-NMR spectra of maleimide-epoxy resin blends, the peak at 170ppm was attributed to conjugated carbonyl carbon of unreacted maleimide, and the peak at 176ppm was non conjugated carbonyl carbon of reacted maleimide, and the peak at 52ppm was methyne carbon of epoxy groups. The reaction processes of maleimide and epoxy groups can be followed by estimating relative intensity of the three peaks.
In curing reaction of maleimide-epoxy resin blends without catalyst, the addition reaction of amino groups to epoxy groups occurred mainly, and the reaction of maleimide proceeded slowly at 170°C. The polymerization of maleimide and the addition reaction of secondary amine to epoxy groups occurred on post curing at 200°C.
In the presence of imidazole catalyst, the polymerization of maleimide proceeded rapidly, but the polymerization of epoxy groups hardly occurred at 170°C. The polymerization of epoxy groups occurred on post curing at 200°C.

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