Swelling - Boujun

This refers to the state in which a solid polymer absorbs a solvent, increases in volume, and becomes gel-like. For example, if a dried hydrophilic gel such as agar or gelatin is immersed in water at room temperature, it will absorb water and swell, but not beyond a certain point. This is called finite swelling. However, in warm water at 60-70°C, it not only swells, but also gradually dissolves. This is called infinite swelling. Raw rubber swells infinitely in benzene, but when crosslinked between polymers through vulcanization, it exhibits finite swelling. When a hydrophilic polymer swells in water, the swelling can be suppressed by adding inorganic salts, and this suppressing effect follows the lyotropic series of salt ions. The pressure exerted when the volume increases due to swelling is called swelling pressure, and it is known to be very large. This type of swelling pressure also appears in dry plant roots and seeds (beans) and wood, and it is known that it can sometimes have a powerful destructive force.

Source: Morikita Publishing "Chemical Dictionary (2nd Edition)" Information about the Chemical Dictionary 2nd Edition

固体高分子が溶媒を吸収して体積が増大してゲル状態になることをいう．たとえば，寒天やゼラチンのような親水性ゲルの乾燥したものを室温で水に浸けておくと，水を吸って膨れるが，ある程度以上には進まない．これを有限膨潤という．しかし，60～70 ℃ の温水中では膨れるだけでなく，しだいに溶解状態になる．これを無限膨潤という．生ゴムはベンゼン中で無限膨潤を起こすが，加硫して高分子間に架橋すると有限膨潤を示すようになる．親水性高分子が水によって膨潤するとき，無機塩類を加えると膨潤が抑制され，その抑制作用は塩類イオンの離液系列に従う．膨潤して体積が増大するときの圧力を膨潤圧といい，非常に大きいことが知られている．乾燥した植物の根や種(豆類)または木材においてもこの種の膨潤圧が現れ，ときには強大な破壊力となることも知られている．

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