A bisphenol A type epoxy resin filled with alumina or silicon carbide (SiC) particles was immersed in an alkaline solution for obtaining the information on their corrosion behavior. Both the alumina/epoxy and SiC/epoxy gradually resolved into the solution from their surfaces. The higher the filler content, the lower was the degree of retention in the flexural strength for the alumina/epoxy. In the SiC/epoxy, the flexural strength decreased remarkably above a specific level of SiC content. The corrosion depth increased linearly with immersion time for the both composites. The higher the filler content and the concentration of alkaline solution, the larger was the corrosion rate. An equation on relationship between the corrosion rate and the filler content (the filler volume fraction) was proposed in consideration of the corrosion promoting effect of the filler particles.

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This article deals with the steric effect of long-chain alkyl groups on network formation in the free-radical crosslinking copolymerizations of alkyl methacrylates (RMA) including hexyl methacrylate, lauryl methacrylate, and stearyl methacrylate (SMA) with trimethylolpropane trimethacrylate (TMPTMA). The incorporation of one TMPTMA unit into a copolymer chain corresponds to the introduction of two or one methacryloyl group, i.e., noncyclic structure unit having two methacryloyl groups or monocyclic structure unit having one methacryloyl group, respectively, and thus, TMPTMA acts as an effective crosslinker. The initial rate of polymerization and primary polymer chain length increased with an increase in the size of the alkyl group in RMA from hexyl to stearyl; this is ascribed to the reduced occurrence of bimolecular termination. The increasing tendency of degree of polymerization with conversion was suppressed in the same order. The deviation of the actual gel point from the theoretical one became greater with enlarged chain of alkyl groups, especially for the copolymerization with SMA. These are related to the suppressed occurrence of the intermolecular crosslinking reaction of sterically crowded growing methacrylyl radical with the pendant methacryloyl groups embedded in the preformed poly (RMA-co-TMPTMA).

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The use of waste steel chips from high-speed grinding processes was examined as an electrically conductive filler in an epoxy resin. The chips were mixed with the liquid epoxy resin, and the mixture was magnetized by being passed through a solenoid coil. The mixture was then cured in an oven. High content of the chips, strong magnetizing currents and high precure temperatures increased the final conductivity of the cured product. By this method, cured products having electrical resistivity of 10² Ω·cm were obtained.

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This review describes an approach to enhance toughness of thermosetting plastics (epoxy, bismaleimide and cyanate ester resins) carried out by our laboratory. Modifiers used include aromatic polyesters such as poly (ethylene phthalate) (PEP), N-phenylmaleimide-styrene copolymers (PMS), poly (ether ketone) s and poly (ester imide) s. Toughening is achieved because of the particulate morphology in the modification by the aromatic polyesters in every case. For example, when using PEP as a modifier, the fracture toughness (K_IC), a measure of toughness, increased 120 % for an aromatic diamine-cured epoxy resin (diglycidyl ether of bisphenol A), 80 % for a bismaleimide resin and 120 % for a cyanate ester resin. When using PMS as a modifier, cocontinuous phase structures are more suitable for toughening the cured resins : the K_IC value increased 130 % for the aromatic diamine-cured epoxy resin, 50 % for the bismaleimide resin and 160 % for the cyanate ester resin. Furthermore, the results of modification by poly (ether ketone) s and poly (ester imide) s were also described briefly.

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Recent topics on in vitro synthesis of polyesters by lipase catalysis are reviewed. Lipase, an enzyme catalyzing an ester bond-cleavage reaction by water in living cells, induces the reverse reaction of hydrolysis, leading to polymer production by a bond-forming reaction. Polyester syntheses have been achieved from various monomer combinations, typically oxyacids or their esters, dicarboxylic acids or their derivatives/glycols, and lactones under mild reaction conditions. By utilizing characteristic catalytic function of lipases, enantio-, regio-, and chemoselective polymerizations proceed to give functional polymers, many of which are difficult to synthesize by conventional methods.

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