Development of Resin-molding-releasing Metal Mold Surface Using Perfluoroalkyl Group-containing Polymer Plating
Kunio MORI*, Hidetoshi HIRAHARA and Yoshiyuki OISHI
Department of Applied Chemistry, Iwate University; Ueda, Morioka-shi 020-8551 Japan
The resin−molding releasing properties of metal molds were shown to be related to following factors: a) interfacial chemical bondings between surfaces of polymers and metal molds and b) a friction force or friction coefficient between polar substances and/or low molecular weight components in the polymers and physical factors on mold surfaces. It was confirmed theoretically and experimentally that metal molds with good resin−molding releasing properties have very small surface free energy. It was also proved that surface free energy in the resulting polymer molding was changed to be lower than that of before shaping. Molding releasing properties were improved with decrease in friction force and friction coefficient between surface of polymers and metal molds as well as decrease of surface free energy.
To obtain metal molds with smaller surface free energy, the polymer plating method of perfluorinated group−containing triazinedithiol was developed. Metal molds treated by the polymer platings have lower critical surface tension of 7.5 mJ m−2 than that of Teflon (18 mJ m−2), meaning that the surface consists of CF3 groups. The treated mold showed more markedly excellent durability in releasing properties than untreated one. The technique has been developed in the production of molds for Fθ lens and natural bright focusing screen.
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