Effects of particle shape and size on Young's modulus of cured epoxy resins have been measured. These resins were filled with irregularly shaped or spherical silica particles. These particles were sorted into six groups having different mean sizes ranging from 2 to 50μ m. In the resins filled with irregularly shaped particles, the flexural and compressive moduli slightly increased with an increase in particle size, whereas in the resins filled with spherical particles, they were not changed with particle size. In both systems, tensile modulus slightly decreased with the increase in particle size. The modulus values for the resins filled with irregularly shaped particles were higher than those for the resins filled with spherical particles in flexural, compressive and tensile moduli. The measured values were always higher in the order of compressive modulus >flexural modulus > tensile modulus.

View full abstract

A detailed investigation on the effect of catalysts on the curing reaction of allyl modified maleimide resins was conducted using model reactions.
Sellecting N-phenylmaleimide (PMI), ο-allylphenol (AP), allylphenylether (APE) and allylbenzoate (AB) as model compounds, the reactions of PMI/AP, PMI/APE and PMI/AB systems were investigated.
Without catalyst, products were 1 : 1 and 3 : 1 adducts of PMI to AP (PMI-AP, (PMI) 3-AP) in the PMI/AP system. Polymerization occurred in the PMI/APE and PMI/AB systems.
Using a radical catalyst (dicumyl peroxide), both PMI-AP, (PMI) ₃-AP and polymer were produced in the PMI/AP system. Polymerization occurred in the PMI/APE and PMI/AB systems as the same in those without catalyst.
Using an anionic catalyst such as 2-ethyl-4-methyl-imidazole, or triphenyl phosphine, the product was PMI oligomers in the all systems and allyl compounds reacted little.
From these results, the effect of catalysts on the functionalities of maleimide and allyl groups was considered.

View full abstract

This paper reports the preparation and cure behavior of several interesting epoxy resins containing SO₂ groups incorporated into epoxy/polyester powder formulations. The cure behavior was examined by gelfraction, DSC, dynamic viscoelastic analyzer, rigid body pendulum viscoelastic analyzer and FT-IR. In each case, the BPS modified epoxy resins exhibit lower temperature cure response in proportion to the number of SO₂ groups. Generally, increasing the level of external curing catalyst in conventional systems lowers the cure response temperature. In this case, however water and salt spray resistance of the cured film is deficient for practical use. The deficiency, can be avoided by modifying the resin components, in that for instance the BPS modification of epoxy resin is effective. The mechanical film properties are also suitable for practical use.

View full abstract

Formaldehyde resins are mainly used for the wood adhesives, because of their exellent properties and cheaper price. In 1989, the output, 530,000 metric tons, was 47 percent of all adhesive production.
The modification with highly-condensated resol, high molecular novolac powder, thermoplastic polymer and isocyanate was investigated for the improvement of ability such as water-resistance, durability, fast curing and toughness.
The reaction mechanism, molecular structure and curing process have been explained with the progress in analysis. Many studies of dynamic viscoelasticity of resin have been continued to clarify the mechanism of wood adhesion.
This paper reviews the recent studies by referring to literatures and patents, mainly published after 1980.

View full abstract