Properties of Extrudable Moulding Compositions Based on a Mixture Aluminum Hydroxides

Abstract

Moulding compositions for extrusive granulation were synthesized based on a mixture of aluminum hydroxides prepared by hydration of thermo activated products of hydrargillite – flush and CTA (centrifugal thermal activated) – in electrolyte solutions (NaOH, H2O, HNO3). The molding compositions were obtained by peptization of the hydroxides with nitric acid free of surfactants. Structural and mechanical properties of the compositions such as elasticity (λ), plasticity (Ps), relaxation period (Θ), etc. were determined using an instrument with a plane-parallel gap, the principle of its operation being based on measuring the time tangential shift. The plastic strength (Pm) and optimal moisture content (ϕ) was measured using the penetrometric method by immersing the working body (cone) into the composition under study. The 1 or 2 structuralmechanical type with predominant propagation of slow elastic deformations was shown to be characteristic of the compositions under study. Ranges of elasticity (λ = 0,39÷0,42), plasticity (Ps = (2÷5,6)·10–6 s–1) and relaxation period (Θ =1700÷3350) were determined. The plastic strength (Pm) and optimal masses moisture (φ) were determined to depend on the preparation conditions of the hydroxides and to range as follows: ϕ = 25,98÷30,83 wt.% and Pm = 11,71÷71,44·104 Pa.