Tensile properties of microbial β‐glucan films

Abstract

β‐glucan films with different plasticizer concentrations (glycerol and water) were deformed in tension and various mechanical characteristics (modulus of elasticity, yield stress, strength, and strain at rupture point) were evaluated. The influence of both plasticizers was of additive nature describable by the total plasticizer content. The influence is reflected by an exponential decrease of either modulus of elasticity or yield stress with increasing total plasticizer content. The film strength decreased linearly with plasticizer concentration, whereas the decline in strain at the rupture point followed a power function. It was also found that the stress parameters can be expressed via modulus of elasticity: the strength as linear function of the square root of the elasticity modulus and the yield stress as a linear function of the latter parameter. On the basis of such relations a quadratic function between strength and yield stress was proposed. This relation well describes the character of the deformation curves that were obtained at different deformation conditions. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers

Stress relaxation and activation volume in tension in β-glucan and chitosan films

“…β (1‐3),(1‐6)‐ d ‐Glucan (hereafter β‐glucan) films were prepared by casting and drying of a suspension of β‐glucan, isolated from baker's yeasts ( Saccharomyces cerevisiae ), with area density 10 mg cm −2 . The final density of the films was approximately 1.3 g cm −3 . Chitosan acetate films were prepared in a similar way.…”

“…The Young's modulus E (MPa) was calculated as the slope of the initial part of deformation curve. The offset yield point (corresponding to an inelastic deformation of 0.2%) was determined .…”

“…In these tests, there were also determined strength and strain at rupture (illustrated in Fig. and described in ).…”

“…The tensile strength, Young's modulus of elasticity E , yield stress as well as other mechanical properties of thin polysaccharide films are sensitively dependent on temperature, stretching rate, moisture content, type and concentration of additives, and on ageing . The shape of deformation curves, consisting of two semilinear parts connected in the yield area, and the influence of plasticizer content on basic mechanical characteristics in β‐glucan films were examined in our previous work .…”

“…Moreover, there could also be detected changes in these mechanisms caused by ageing. The article can be understood as a free continuation of our previous work in which the simple tension of β‐glucan films and loading/unloading tests were studied.…”