(183ai) Application of Hansen Solubility Parameter to Transparency Evaluation for Composite Materials

In recent years, plastic film has attracted attention as substitutes for glass in display materials. Properties generally required as a plastic film include high heat resistance and mechanical strength. However, it is difficult to express the target function with only a single resin. Therefore, in order to express the target functions, a method of adding inorganic materials such as silica to the resin is used. It is possible to realize materials having high heat resistance and mechanical strength. However, as a problem, transparency may be reduced due to the addition of different substances to the resin. In general, when designing materials, we have repeatedly experimented with trial and error in order to express necessary functions while maintaining high transparency. So, a cost, labor and time of experiment are required. Therefore, it is necessary to predict whether the transparency is reduced when the filler is added to the resin in order to streamline the material design. As a method of predicting the transparency of the single resin, the method of predicting from the molecular structure has been reported. However, no prediction method for transparency at the time addition of filler has been reported in solvents and resins. Therefore, We focused on Hansen solubility parameter (HSP), which has been used to evaluate the physical properties of fine particle surfaces, as a predictor of transparency.

HSP is physical property that indicates the cohesive energy density of each substances. It is useful for evaluating the compatibility, wettability, cohesion and dispersibility of substances. Hansen considered that the three main forces of dispersion force, intermolecular dipolar interaction, and hydrogen bonding interaction act in the interaction between substances. And he defined Hildebrand solubility parameter as HSP consisting of three factors.As an application example of HSP, it is used for the affinity evaluation between substances, such as the dispersibility evaluation of fine particles and the solubility of various substances. It is also reported that each term of HSP of the solvent has a correlation with the physical property value. In particular, the dispersive power term of HSP is reported to be related to the refractive index.

In this experiment, it was examined whether transparency in solvents could be evaluated using HSP using model particles. Several types including silica particles were selected as model particles. HSP of each model particle was determined and dispersed in solvents in which HSP is known. The transparency was examined from the light transmission in various dispersion media. As a result, it was confirmed that the difference in the dispersion power term of HSP between each particle and the solvent affects the transparency.