Effect of interfacial adhesion on the flexural strength of an epoxy resin filled with spherical silica particles was investigated. There were used five kinds of spherical silica particles having different mean sizes in the range from 2 to 30 mm. The particle content in the resin was 50% by weight. In order to prepare the well and poorly bonded interfaces between the particle and matrix, the particles were treated with silane coupling and decoupling agents, respectively. Both of the treated-particle-filled resins were compared with the untreated-particle-filled one. The flexural strength was higher in the following order : well-bonded > poorly bonded > untreated. From the scanning electron microscopic observation of fractured resin surfaces, the fracture strength of particle-filled brittle resin was found to be affected by the number and sharpness of defects in the material derived from the particle fracture or interfacial debonding.

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Polyol development is critical in order to develop a two-component waterborne polyurethane coating that can attain a 250 g/L VOC while maintaining performance requirements.
This paper discusses a statistical study to develop a 250g/L, two-component water reducible polyurethane coating using a tertiary isocyanate crosslinker with dry times and reactivity equivalent to a two-component solventborne system. The effects of acrylic molecular weight, glass transition temperature (Tg), and hydroxyl concentration on viscosity and dry time have been analyzed and statistical models identified that describe the relationships between these experimental factors and responses. Contour plots show tradeoffs between obtaining a low viscosity resin and maintaining fast dry time of the applied formulation.
The data from the statistical study suggests that it is difficult to achieve the overall performance desired for an automotive refinish system with the simple four-component acrylic system investigated. The addition of either a longer chain hydroxyl functional monomer or styrene in the acrylic polyol improved the overall performance of the system. Faster cure was also demonstrated with an alternate catalyst.

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As part of our continuing studies concerned with the elucidation of three-dimensional network formation mechanism in the free-radical crosslinking polymerization of multivinyl compounds, this article deals with the pursuit of network formation processes beyond the gel point in the copolymerization of methyl methacrylate (MMA) with ethylene dimethacrylate by ESR spectroscopy, especially focusing on the microheterogenization of network structure. Thus, poly (MMA-co-CuMAOTPP) s were prepared by the copolymerization of MMA with copper (II) methacryloyloxyphenyl tetraphenylporphyrin (CuMAOTPP) and their usefulness as polymer spin probes was examined as compared with its low-molecular-weight counterpart or copper (II) tetraphenylporphyrin (CuTPP). Poly (MMA-co-CuMAOTPP) of moderate molecular weight, i.e. about 20,000 was more useful than CuTPP for ESR spectroscopic investigation, but the polymer spin probe having 95,000 of molecular weight decreased its effectivity reversely. Then, the correlation between ESR spectra and microheterogeneity of networks formed under various polymerization conditions was examined by changing the factors influencing resultant network structures, including monomer concentration, crosslinker content and flexibility of network segments. Clearly, the mobility restriction of polymer spin probe by network formation was reduced under the conditions introducing inhomogeneous networks as a reflection of the exclusion of polymer spin probe into void part of a gelled system. Finally, the quantitative discussion on the microheterogeneity of network structure was attempted by simulating the observed ESR spectra.

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