Adhesives. Wood adhesives. Determination of static load resistance with increasing temperature

Abstract This study deals with the rheological properties of wine lees. Samples of wine lees of the Saint Laurent variety were used in this experiment. The investigated wine lees arose in the process of production red grape wine in 2013 (Czech Republic). At first, the chemical background was determined. The chemical background includes the following chemical parameters: total acidity, pH, alcohol content, reduced sugars, free SO2, total SO2, and volatile acid. In the second phase of the study, physical properties were determined. Specifically, a sample of wine lees was subjected to rheological tests. These tests consisted in determination of dependence of dynamic viscosity on the temperature, hysteresis loop tests, dependence of dynamic viscosity on the time and step-down in the shear rate test. The experiment demonstrated that the dynamic viscosity increased with increased temperature – this phenomenon is caused by thermolabile proteins – and the wine lees has rheopectic behaviour; the degree of rheopexy was found to rise with the increasing temperature.

Download Full-text

Increasing contribution of grain boundary compliance to polycrystalline ice elasticity as temperature increases

Journal of Glaciology ◽

10.1017/jog.2018.56 ◽

2018 ◽

Vol 64 (246) ◽

pp. 669-674

Author(s):

COLIN M. SAYERS

Keyword(s):

Grain Boundary ◽

Grain Boundaries ◽

Orientation Distribution ◽

Resonant Ultrasound Spectroscopy ◽

Wave Velocities ◽

Polycrystalline Ice ◽

Resonant Ultrasound ◽

Increasing Temperature ◽

Shear Compliance

ABSTRACTMeasured elastic stiffnesses of ice polycrystals decrease with increasing temperature due to a decrease in grain boundary stiffness with increasing temperature. In this paper, we represent grain boundaries as imperfectly bonded interfaces, across which traction is continuous, but displacement may be discontinuous. We express the additional compliance due to grain boundaries in terms of a second-rank and a fourth-rank tensor, which quantify the effect on elastic wave velocities of the orientation distribution as well as the normal and shear compliances of the grain boundaries. Measurement of the elastic stiffnesses allows determination of the components of these tensors. Application of the method to resonant ultrasound spectroscopy measurements made on ice polycrystals enables determination of the ratio BN/BS of the normal to shear compliance of the grain boundaries, which are found to be more compliant in shear than in compression. The ratio BN/BS is small at low temperatures, but increases as temperature increases, implying that the normal compliance increases relative to the shear compliance as temperature increases.

Download Full-text