Effect of Water Glass Modification on Its Viscosity and Wettability of Quartz Grains

A Kmita,B Hutera

doi:10.2478/v10266-012-0082-1

Abstract

Abstract The aim of the present study was to develop a modifier for water glass. The method of thermal generation of metal oxide nanoparticles was adapted and used in the research. Nanoparticles of ZnO from the thermal decomposition of basic zinc carbonate were used. A method for the modifier introduction was developed, and the effect of modifier content and organic solvent type on the physico-chemical properties of binder (viscosity) and quartz wettability was determined. Binder viscosity was examined from the flow curves plotted with the help of a RHEOTEST 2 rotational rheometer equipped with proper software. Quartz wettability was determined examining timerelated changes in the value of the contact angle in a quartz-binder system, until full stabilisation of the angle value has been achieved. Binder modification was carried out on sodium water glass designated as R"145". The water glass modifiers were suspensions of ZnO nanoparticles in propanol and methanol at a fixed concentration of c = 0.3 M and with the size of nanoparticles comprised in a range of <61 - 981 nm>. Water glass modification with the suspensions of ZnO nanoparticles in methanol and propanol showed the effect of modifier on the water glass viscosity and quartz wettability. This effect depends on the type of alcohol used. The ZnO suspension in propanol (alcohol with a longer hydrocarbon chain) affects more strongly the viscosity of binder and quartz wettability than the methanol suspension

Highlights

Moulding sands with organic binders exhibit significant toxicity
All the flow curves (Figs. 1, 2 and 3) are straight lines extending from the origin of a coordinate system (γ, τ), which indicates a Newtonian nature of the binder with characteristic for this type of fluids rheological parameter - viscosity η (1): τ = η · γ where: τ – the tangent stress, η – the absolute viscosity, γ – the shear rate
The presented results show that water glass modification with alcohol suspensions of nanoparticles affects the intermolecular phenomena

Summary

Introduction

Moulding sands with organic binders exhibit significant toxicity This involves, on the one hand, the necessity of additional investments to ensure an adequate level of safety and proper working conditions in foundries, while, on the other, increases the sand cost, especially when it contains binders with furfuryl alcohol. These drawbacks forced the researchers to look for binders that do not show these characteristics. This is because the technological process should simultaneously meet the following demands: ensure optimal conditions for the core and mould hardening, ensure the required level of mechanical and physico-chemical properties (strength, hygroscopicity, brittleness, etc.) as well as the lowest possible residual strength of moulds and cores in a wide range of temperatures (300-1200°C), which will improve the knocking out properties of the sand and, last but not least, will improve the moulding and core sand reclamability

Objectives

Methods

Results