Effect of low molecular weight materials on physical and mechanical properties of gelatin films

A study was made of low molecular weight substances on the heat stability, thermal contraction and mechanical properties of gelatin films. It was shown that the heat stability of gelatin decreases considerably on adding compounds containing more than two polar groups and which have no marked effect on the helical structure of gelatin. For materials, which hinder spiralling in gelatin macromolecules during film formation it is not the temperature but super-contraction which decreases. It was found that the effect of low molecular weight substances on thermal contraction of gelatin films (at 20 to 120°), is correlated with their effect on the temperature variation of super-contraction of gelatin. Materials which reduce the thermal contraction of gelatin films normally reduce heat stability. Mechanical properties of gelatin films depend on the structural ordering and moisture content of gelatin. Materials which reduce the spiralling of gelatin macromolecules, or lower the moisture content of the gelatin system increase the brittleness of gelatin films. The elastic properties of films increase if materials introduced enable the moisture content of films to be increased considerably without altering the structure of gelatin.