Shape memory of composites based on silicone rubber and polyacrylamide hydrogel

The shape memory of hydrophilic composite materials based on silicone rubbe r and slightly crosslinked polyacrylamide, which is a non-ionic hydrogel, h as been studied. Before the shape memory testing, it was necessary to deter mine the glass transition temperature (T-g) of the slightly crosslinked pol yacrylamide as well as the mechanical properties of the composites at tempe ratures above T-g of a crosslinked polyacrylamide. Afterwards, the shape me mory of the composite material was tested by performing a set of simple exp eriments based on deformation and heating of test pieces, their subsequent cooling and deformation force removing, and their repeated heating or water swelling, during which the residual elongation was measured and calculated . The composite material shaped in this way resumes its original shape if i t is again heated above T-g of the crosslinked polyacrylamide or allowed to swell in distilled water. There exists a limiting concentration of hydroge l phase (approx. 30 phr), which is limited by good dispersion and good cont act of hydrogel particles within the silicone matrix, under which the shape memory does not occur, and above which it exists.