Dynamic mechanical properties of geopolymer-polymer composites

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Title: Dynamic mechanical properties of geopolymer-polymer composites
Author: Shrotri, Kunal
Abstract: Dynamic mechanical properties and rheology of the organic polymer modified inorganic polymer systems synthesized from metakaolin were studied and evaluated. These inorganic polymers, popularly known as geopolymers, possess a set of excellent characteristics which includes high compressive strength, high temperature and fire resistance, acid resistance, heavy ion fixation, low temperature curing, good surface finish, low cost raw materials and are environment friendly. Geopolymers are a relatively new class of engineering materials and are in the process of finding their way to industrial products. A few of the problems that are holding back the development of these materials are the control of curing rime, enhancement of their workability and knowledge of the dynamic mechanical properties of these systems. In this project the control of curing time, improvement in the workability and modification of the rheology was achieved by addition of organic polymers including poly (ethylene glycol) and carboxy methyl cellulose, to the geopolymer system. The dynamic mechanical properties of these systems were evaluated using dynamic mechanical analysis for the cured systems in the plaque form and a rheometer for the uncured systems as slurries. The effect of organic polymers on the geopolymer system was quantified using the same techniques. Poly (ethylene glycol) is commercially used as a plasticizer to increase the lubricity of the ceramic mass and has excellent spreading properties. Carboxy methyl cellulose, a modified polysaccharide, is commercially used as a viscosity modifier and has an excellent water retention capacity. These two organic polymers were added to the geopolymer system with an aim of modification of rheology, processability and dynamic mechanical properties before and after curing. Addition of these polymers to the geopolymer system varies the curing time of these systems in the range of 4 hours to 72 hours. Also the rheology of the uncured slurries is changed. This was quantified using the theological studies that show increase in the elastic and viscous moduli of the slurries after addition of the organic polymers. The elastic modulus varied between the range of 7 Pa to 54,600 Pa depending on the polymer and water content. Similarly, the viscous modulus also varied between 1 6 Pa and 25,400 Pa. The increase in the elastic modulus of the uncured slurry is significantly more than that of viscous modulus. The viscosity of these systems with respect to time and shear rate was also observed and showed change after addition of organic polymers. The viscosity varied within the range of 4 Pa.s to 580 Pa.s depending on polymer and water content. The composite slurry exhibited thixotropic behavior. These uncured slurries were cured to form cheesecloth-reinforced plaques. These plaques were used to study their elastic and viscous moduli with respect to temperature using the dynamic mechanical analysis technique. The results are encouraging and showed improvement in the moduli of the systems after addition of organic polymers for a selective loading range. But largely addition of organic polymers had a negative impact on the dynamic mechanical properties of geopolymer system. Addition of organic polymers also imparted flexibility to the cured samples opposing to the brittle nature of the pure geopolymer systems.
Record URI: http://hdl.handle.net/1850/14286
Date: 2006-02

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