It is well known that in the synthesis of Phenol Novolac Resins, molecular weight and molecular distribution are determined by the molar ratio of phenols and aldehydes. In order to prepare a type of Phenol Novolac Resins of low molecular weight with narrow molecular distribution, it is usual to lower the value of F/P (ratio of formaldehyde and phenol), by which excessive volume of phenols are to react with formaldehydes. But in this case, it is very much likely to see so much volume of unreacted phenols left.
In this paper, a new method of synthesis of naphthol-modified phenolic resins, which has settled such problem, is to be reported. By this new method of synthesis, under the existence of strong acid between the reflux reaction and the vacuum condensation reaction, lower molecular weight and narrower dispersion of molecular distribution were aimed to be accomplished through the maintenance of such condition as to keep water at the temperature of 150°C for longer than one hour. This Splitting-Recombining Reaction is generally taken place at such condition where naphthol and strong acid such as hydrochloric acid and PTS are in co-existence, although the Reaction would be rarely taken place at such condition where weak acid such as oxalic acid and zinc acetate were in existence. Further, it was found that this Reaction progresses under such condition where any other phenol is present so far as naphthol should be there. And it was also found that the degree of low molecular weight is larger at the higher range of F/P ratio.

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A new method to cure phenolic resin is described. Novolac resins diluted with a multifunctional-reactive-solution-type-compound such as divinylbenzene, can be cured by adding Lewis acids (i.e., aluminum chloride) or protonic acids (i.e., sulfonic acid) as a curing catalyst. There are discussed such things as the effective types of novolac resins, mixing ratios, the evaluation of cured compounds, the reaction mechanism, and the analysis of structure. While conventional novolacs have low compatibility with divinylbenzene, low molecular weight resins with a high ortho-oriented structure shows very good solubility, thus forming a homogeneous solution with low viscosity (a liquid component). The liquid component can be cured by adding cationic catalyst at RT or higher. The addition of the vinyl group in divinylbenzene to the activated site in the phenolic nuclear enables the cure to proceed without gas formation. This makes easy to handle the resin. Properties of the cured resin are well balanced, especially enhanced in mechanical strength, heat resistance, and waterproofing. Also the resistance to alkalis, which is lacked in the conventional phenolic resins, is excellent. The phenolic resin with the new curing system, therefore, is highly expected to be used in various application fields.

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The curing of an epoxy / anhydride system was analyzed using microdielectrometry and differential scanning calorimetry. Microdielectric measurement may be available for collecting on-line real-time data during a casting process.
The change of equivalent resistivity measured by microdielectrometry was investigated in connection with the extent of conversion and glass transition temperature obtained from the analysis of DSC. The curing temperature and time related to an equivalent resistivity could be described by Arrehenius law. The relation between the conversion and Tg was applied to the kinetics equation established by DiBenedetto. The equivalent resistivity (ρ) was proportional to the difference between a cure temperature (Tc) and Tg, and applicable the equation ρ=ρ₀exp [A/fg + a (Tc-Tg)] that was introduced by a free volume analysis.

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Thermosetting resins have been supposed not to be recycled because of their insoluble and infusible properties, and most of them have been disposed by burning or reclamation. But now this becomes a big problem due to environmental pollution by burning, cost of reclamation, or difficulty of obtaining places for reclaimation. Then recently, various recycling technologies for thermosetting resins have been developed. They are broadly divided into three categories as follows : (i) material recycling; reusing as fillers, additives, or extenders, (ii) chemical recycling; reusing as monomers or oligomers by pyrolysis, or as charcoal by sintering, (iii) energy recycling; reusing as combustion energy. This report introduces recent examples on the recycling of thermosetting resins, such as phenolics, polyurethanes, and unsaturated polyesters.

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