Dora Kroisová

Composites Base on Geopolymer Matrices: Preliminary Fabrication, Mechanical Properties and Future Applications

Geopolymer matrice Composites are fabricated at room temperature or thermoset in a simple autoclave. After approximately four hours of curing, composite materials exhibit excellent properties. Finding applications of geopolymeric composites in all fields of industry are the hot topics. This paper covers: (i) mechanical properties of fibers: carbon, Saint-Gobain Cemfil/CFV alkali resistance glass (various types), ARG-NEC (Nippon electric Columbia) alkali resistance glass, E-glass for pultrusion, AR glass for pultrusion were evaluated in accordance with Japanese Industrial Standard (JIS R 7601). (ii) properties of geopolymeric matrices: geopolymeric matrices are fabricated from various types of geopolymeric resins that were made at Research Institute of Inorganic Chemistry, Inc., Czech Republic and testing for mechanical properties, and by SEM for structure characterization. (iii) fabrication procedures of geopolymer matrix composites with carbon and other fiber reinforcements. (iv) results of mechanical testing of geopolymer composites, SEM for adhesion between the matrix and reinforcement, and (v) Results and discussion.

New Generation of Geopolymer Composite for Fire-Resistance

The most popular matrix used for fiber-reinforced industrial composites is organic polymer. The nature flammability of the organic polymer matrix (Marsh, 2002), however, limits the use of these materials in ground transportation (Hathaway, 1991), submarine and ships (Demarco, 1991), and commercial aircraft (Davidovits, 1991), where restricted egress of fire hazard is an important design consideration, although traditional fibers, such as carbon and glass fibers or new developed, high temperature, thermal-oxidative stable fibers from boron, silicon carbide and ceramic are inherently fire resistant (Papakonstantinou et al., 2001). In other word, most of organic matrix composites cannot be used in applications that require more than 200 oC of temperature exposure. In these cases of applications, composites based on carbon matrix or ceramic matrices are being exploited. However, use of these materials is even strongly limited, due to high cost accompany with special and high-thermal processing requirements (Papakonstantinou et al., 2001; Papakonstantinou & Balaguru 2005). In 1978, Joseph Davidovits proposed that binders could be produced by a polymeric reaction of alkaline liquids with the silicon and the aluminum in source materials of geological origin or by-product materials such as fly ash and rice husk ash (Davidovits, 1999). These binders have been coined as term geopolymers since 1979; they are inorganic polymeric materials with a chemical composition similar to zeolites but without defined crystalline structure and possessing ceramic-like features in their structures and properties. The amorphous to semi-crystalline three dimensional of sialate network consists of tetrahedral SiO4 and AlO4 which are linked alternately by sharing all the oxygens to create polymeric Si-O-Al bonds (Davidovits & Sawyer 1985; Davidovits, 1991). Geopolymers are still considered as a new material for coatings and adhesives, a new binder for fiber composites, and a new cement for concrete (Davidovits, 2008). They are mineral polymers and the essence of all mineral polymers is never burn (Davidovits, 2008). Therefore, we can state that geopolymer materials are ideal for high temperature and fire applications. Fiber-reinforced composites based on geopolymer matrix (geocomposite) have been wellknown for over 20 years, since the first Davidovits’ patent was filed (Davidovits et al., 1989).

Water Desorption Kinetics of Polymer Composites with Cellulose Fibers as Filler

The water desorption kinetics of polymer composite systems with hydrophilic cellulose fibers from recycled paper (PSP) filler embedded in various polymer matrices (hydrophobic thermoset epoxy resin [EP] and thermoplastic polypropylene [PP], and hydrophilic thermoplastic poly[vinyl alcohol] [PVA]) was studied. Polymer composites test pieces containing 0, 3, 6, 9, and 30 wt. % of fibers were prepared. Adhesion between fibers and polymer matrices was improved by utilization of maleic anhydride grafted polypropylene (MAPP) coupling agent in the case of thermoplastic matrices (both PP and PVA). Water desorption tests were conducted after immersing test pieces in a distilled water bath at room temperature for 24 h. Study of the water desorption kinetics proved the expected enhanced absorption of the resulting composites after incorporation of cellulose fibers. A difference between two similar types of PVA by measurement of the desorption kinetics was found.

Thermophysical properties of woven fabrics reinforced geopolymer composites

The aim of this study is to determinate thermophysical properties (thermal diffusivity, thermal conductivity, specific heat and thermal expansion) of geopolymer composites reinforced with different types of woven fabrics. Many reinforcements and geopolymer matrices are now available, but our work was focused on geopolymer matrix Q13K1, which involved common of thermal silica, kaolin, and potassium water glass; and combination with fabric E-glass, basalt and carbon fibers were also investigated. The samples were prepared using a standard vacuum bagging technique. The fabrics were impregnated with the matrix by-hand, stacked together and placed in the vacuum bag. Thermophysical properties were determined in accordance with national and international standards such as ASTM E-1461, DIN 30905, DIN EN 821, DIN 53752, etc.

Chapter 2 – Microstructures and Nanostructures in Nature

Abstract A description of the selected structures for natural plant and animal objects is the content of this paper. The aim of this paper is to show that the optimal structures already exist in natural materials which have been developing for millions of years. These structures have been created so that to provide during their life functions they perform such as mechanical loading and plant materials surface cleanness in connection with the ongoing photosynthesis process. Surface structures of common plant types and interesting structures identified for animal objects associated with their behavior are described in the paper.

Rice Husks - Structure, Composition and Possibility of Use them at Surface Treatment

Rice husks (RH) are characterized by a high content of silicon dioxide up to 23 wt. %. Silica in the form of nanoparticles creates surface layers formed in various plant parts which ensure protective properties and mechanical stability. These nanoparticles with a dimension in the range of tens of nanometers, are formed during biochemical processes and photosynthesis. Individual nanoparticles are interconnected between themselves and between layers with organic phase via cellulose fibres. Accompanying ions mainly potassium, calcium, sodium, magnesium and aluminium extremely important for plant growth have also been identified in rice husks. In this research paper we investigated mechanical properties of composite epoxy resin material, which was composed of ChS Epoxy 520 filled with silica obtained from rice husks. Nanoparticles of silicon dioxide with the size in dozen of nanometers were prepared by calcination of raw plant parts. We found that the 0.1 phr of filling (0.01 g of filler + 10 g of epoxy) demonstrated a significant increase of wear resistance and decrease of coefficient of friction. An excellent adhesion between epoxy resin and silica nanoparticles was also observed. The silicon dioxide in epoxy resin plays the role of the hard phase, which transfers part of the load and protects the surface of polymer against wear. The presence of this filler does not change the mechanical properties of the original resin.

Structure and Properties of Selected Natural Materials

This paper deals with description of properties of selected natural materials mainly theirs shelter function. The investigated materials are horsetail and walnut shell. Both natural materials have porous shell/tubular structure. Walnut shell provides natural shield cover for fruit with gradient distribution of porosity and membrane function. In case of horse tail, except the gradient distribution of porosity there is also the gradient change of chemical composition along the cross-section.

Use of Geopolymer Matrix Composites in the Construction of Fire Doors

Protection and safety of workers in plants with the danger of fire is always the first place. They are currently used in devices that are designed to quickly separate the fire residues from workers such as steel fire doors filled with non-combustible materials that insulate the prescribed time up to 600 ° C. As the demands for safety was the requirement for resistance to temperatures higher than 600 ° C. [1, 2]. Post relates to improvements refractory properties of steel gates based geopolymer matrix composites. They are analyzed the properties of different materials such as fillers geopolymer matrix, durability and affinity to steel parts of the door structure.