Effect of Sodium Chloride on Elastic Behaviour of Silicone Matrices

Overview

An increase in the availability of the active ingredient from silicone matrices can be achieved byusing sodium chloride as the filler. An addition of sodium chloride also influences the mechanicalproperties of silicone systems. The temperature dependence of real Young’s model E’ of additionsilicone systems with sodium chloride was measured. With increasing NaCl concentration in thesilicone system, the values of Young’smodule E are increased. The increase is also influenced by theparticle size of NaCl. The values of the module are moderately increased also with increasingtemperature, which corresponds to the kinetic theory of caoutchouc elasticity. A significant increasein E takes place at NaCl concentrations higher than 20 %.With a 50 % NaCl content in the system,E is increased approximately 3.5 times in comparison with an unfilled sample. Various theories ofelastic behaviour of composites can be employed for the description of the effect of the filler on themechanical properties of silicone systems under small deformations. The effect of chloride is bestdescribed by the relation proposed by Nielsen. The value of the constant A in Nielsen’s relation,dependent on the shape of the filler particles and Poisson’s constant of the unfilled matrix, decreaseswith increasing particle size.With a change in particle size, a certain change in particle shape takesplace. Hydrodynamic theory provides good results for sodium chloride particle size of 102.5 µm, butfor particle sizes of 20 µm and 60 µm it is less successful than Nielsen’s relation.

Key words:
silicones – mechanical properties – fillers – sodium chloride