| abstract |
A technique by which the strength of a gel can be improved without impairing excellent properties of the gel, such as high flexibility and high water retention; and various uses of the gel. In the gel, a crosslinked polymer constitutes the basic skeleton of the gel and forms a rigid network structure having scatteringly distributed vacant parts which are extremely sparse parts in the network, while an uncrosslinked polymer localizes in these vacant parts and is physically entangled at end parts thereof with the network structure of the crosslinked polymer while retaining flexibility. In the gel having a semiinterpenetrating network structure, crack propagation over a long distance cannot occur as long as an extremely large external force exceeding stresses diffusible by the uncrosslinked polymer is not applied. Even when a fracture occurs microscopically, it does not become a macroscopic fracture under these conditions. This gel never break unless an extraordinarily large external force is applied, because the critical value leading to a macroscopic fracture is extremely high. |