Rheological modifiers based on cellulose nanoparticles applied in additive manufacturing (3D printing) of geopolymers

Abstract

The term geopolymer delimits a family of inorganic polymer materials with high compressive strength, fire resistance and high temperatures, high resistance to acid attack, ability to immobilize heavy ions and low curing temperature, synthesized by means of chemical reactions in which minerals as the silica and the alumina can react with Me2SiO3 (Me - Na or K) or H3PO4 to form compounds with Si - O - Al - O or Si - OPO - Si [1] bonds. The excellent properties of geopolymers attracted the attention of researchers in the area of refractories, special concretes and biomaterials [2,3,4], among others, on a global scale. Due to the rapid growth of ceramic manufacturing by additive manufacture and the recognition of the potential of geopolymers, the technique has become a route with great commercial potential for the manufacture of geopolymer products [5]. The feasibility of this processing route, however, depends on the ability to modify and control the rheological properties of the geopolymer suspensions. The ideal suspension for direct additive manufacture is a thixotropic fluid with low initial flow stress and viscosity that decreases with increasing shear rate. In this way, the suspension can be easily extruded by forming at relatively low pressures and at the same time retaining the shape after deposition. This behavior can be developed in suspensions with particulate materials by means of flow modifying additives such as binders and polymeric plasticizers. Among the various polymers used in industry and research laboratories, plant-derived cellulose stands out as the most abundant renewable and biodegradable polymer on Earth [10,11]. The potential of nanocellulose in the field of additive manufacturing has been proven in several recent research [12-14]. The expected result in this research project is the definition of the relationship between the characteristics of nanocellulose and its performance as rheological modifier of geopolymer suspensions. (AU)