FRACTURE PROPERTIES OF KONJAC MANNAN GEL - EFFECT OF GEL TEMPERATURE

Fracture properties of 2% konjac mannan (KM) gels were determined by torsion testing at several temperatures. Two treatments were evaluated: 3:1 and 2:1 ratios of alkali:KM (v/w). Capstan geometry gels were equilibrated to 5, 20, 35, 50, 65 or 80-degrees-C. Shear stress at fracture was invariant with test temperature. This response suggests a permanently bonded network. However, there were no covalent links believed to be present in stabilization of KM gels. Shear strain at failure decreased linearly with increasing temperature, a typical response of entropy elastic gels. It is observed that the 'total' strain at fracture, the sum of mechanically produced strain and internal thermal motion strain, remains constant throughout the range of test temperatures. Total strain was estimated at approximately 3.4 by extrapolation to absolute zero. KM gels. although probably not covalent in nature. respond to mechanical deformation as permanently bonded systems during the short stress times involved in the present study.