FIG. 35 Relationship between defoaming performance evaluated by the cylinder shaking test and the contact angle=θ (a), and the 10-point height irregularities= Rz of various kinds of developed silicone resin antifoams (b).

No significant correlation could be found in this figure between the defoaming performance and the hydrophobicity (contact angle) of the silicone resin particle. However, the defoaming effect evaluated by the cylinder shaking test correlated highly to the Rz values as shown in Fig. 35 [223]. And it also shows that the solid particles of light specific gravity tend to have a high defoaming effect. Furthermore, the antifoaming performance of these particles is confirmed in the drum-type laundry washing machine (Fig. 36). In the case of no antifoam, foam filled up the inside of the machine after 20 min. When the mixed-type antifoam was added, little foam was observed in the first 10 min, but after 10 min foam gradually appeared, and finally increased to 15 cm in height. This phenomenon suggested that the antifoaming performance of this type decreased with time or was influenced by increasing temperature. On the contrary, when the silicone resin particle was added, foam was generated within a few minutes; it did not, however, increase with time. This result shows that this particle has a high antifoaming performance and durability.