Preparation of hybrid nanocomposites based on urethane acrylate resin and natural nanoclay fibers and their properties

Master's Thesis in Polymer Science and Technology Engineering

Abstract

Due to their low viscosity and flame retardant properties and relatively easy curing, urethane-acrylate resins are of interest. On the other hand, natural fibers with renewable resources, low price, low density and high special properties have a special ability to be used in composites. However, their relatively high moisture absorption and flammability, compared to carbon fibers and glass, have limited their use. Combining urethane-acrylate resin with natural fibers can create good physical and mechanical properties. On the other hand, the presence of particles in nano dimensions can have favorable effects on their mechanical, thermal and water absorption properties. In the first phase of this project, urethane-acrylate resin (Modar) was combined with nanoclay in different weight percentages using a homogenizer and an ultrasonic bath. The samples needed to perform physical and mechanical tests were made using a silicone mold and by casting method. The distribution of nanoparticles was investigated using TEM, XRD and viscosity measurement techniques. The mechanical properties including (tensile, bending and impact) and the physical properties of the resulting nanocomposites including (hardness, burning speed and water absorption) were investigated. In the second phase of the research, natural fibers of flax were prepared by the silane coupling agent called Trioto Kesi Vinyl Silane. With this description, in order to observe the effect of the silane coupling agent and also the distribution of clay nanoparticles in the resulting composite and hybrid nanocomposites, this part of the project was divided into three parts: in the first part, composites based on urethane-acrylate resin reinforced with unmodified fibers (FRP) were prepared, so that with the introduction of the silane coupling agent in the second part, the effect of improving the interface on the physical and mechanical properties of composites reinforced with modified silane fibers (FRST) was investigated. In the third part, in order to determine the effect of clay nanoparticles on the physical and mechanical properties of hybrid nanocomposites reinforced with modified flux fibers (FRSTN), a nanocomposite containing 3% by weight of total nano was used as the matrix phase. Composites and hybrid nanocomposites reinforced with modified and unmodified fibers were prepared by resin molding process under vacuum. The improvement of the interface of the composite and the above hybrid nanocomposites by the silane coupling agent was followed by SEM images. The presence of clay nanoparticles and silane coupling agent in the polymer matrix and the surface of natural fibers, respectively, was investigated by EDXA technique. Finally, the physical and mechanical properties of the composite and hybrid nanocomposites prepared in the second phase were measured, and the effects of the silane binding agent and clay nanoparticles were investigated.

The results showed that the addition of clay nanoparticles was effective in improving the physical and mechanical properties of the composites prepared in the first phase, and the most optimal properties were observed in the nanocomposites containing 3% by weight of clay nanoparticles. It has also been observed that the modification of flax fibers by triethoxyvinyl silane and then the addition of nanoparticles to the modified composites has improved the physical and mechanical properties of composites reinforced with fibers in the second phase. In contrast to conventional and common composites, nanocomposites have a feature in which fillers with a size of less than 100 nm are used in at least one dimension. One of the advantages of polymer nanocomposites is that it gives several properties to the primary polymer, despite the fact that it creates less limitations in its processability than other reinforcements [1]. The key to these features is in the design and behavior of polymer nanocomposites, which includes the size and properties of the filler nanoparticle and the interface between the filler nanoparticle and the matrix[2].

In the not-so-distant past, the basis of new polymer nanocomposites was carbon nanotubes[1], on which extensive research was conducted.The inherent clustering and aggregation of carbon nanotubes and the high cost of its production have limited the use of these materials [3]. In the meantime, graphene [2] as an alternative promising for the production of new polymer nanocomposites has attracted attention due to its excellent properties including thermal, electrical, mechanical and physical properties[4]. does not exist. For example, in the aerospace industry, there is a need for materials that have high strength, lightness, wear resistance and good resistance to ultraviolet light and do not lose their strength at high temperatures. Since it is difficult to find materials that have all the above properties, it is better to look for a method to combine the properties of materials, this solution is the use of composite materials. In this research, research activities were carried out in the field of resol/graphene/carbon fiber hybrid nanocomposites in order to identify the effective parameters in their preparation and optimum percentage composition, and then to investigate the role of graphene sheets on curing, thermal resistance, morphology and chemical structure of phenolic resin, as well as resin adhesion to fibers and the resulting mechanical properties.

1-3-Research background

1-3-1-Phenolic resins

Phenolic resins or phenol-formaldehyde resin, sometimes called phenoplast[3], is a resin obtained from the reaction of phenol or its derivatives with an aldehyde, which is usually the aldehyde used in formaldehyde. The production of this resin was started in 1905 by Backland [4]. He understood the methods of controlling and developing the reaction to obtain a useful product and in 1907 he succeeded in obtaining the first points in this field. Although the reaction between phenol and aldehydes was known long before this date, by adding mineral fillers and wood powder to the resin, he prepared suitable molding materials and molded them under pressure and temperature, and opened the first company manufacturing these materials under the name Bakelite [5] in Germany in 1910. Phenolic resin reinforced with fabric was also produced in 1930 [5].

1-3-2- Graphene nanocomposites

The field of nano-related technologies was developed more than 25 years ago and its importance is increasing day by day. Recently, nano materials have been assigned a wide range of applications due to their structural characteristics, however, material scientists are looking for materials with good physical properties that are in the nano range in terms of dimensions. From this point of view, the discovery of graphene and polymer nanocomposites based on it is very important in the field of nano science and plays a key role in new knowledge and technology. In general, the use of inorganic nano materials as a reinforcement in the production of polymer/mineral composites has received much attention due to their unique properties, and they are used in the automotive, aircraft, construction, and electronics industries. Major researches have been focused on polymer nanocomposites based on layered materials from natural sources such as Montmorillonite [6] of silicate compounds and synthetic clay. The electrical and thermal conductivity of clay is very weak, so in order to solve this problem, carbon-based nanofillers such as carbon black [7], carbon nanotubes, graphene and carbon nanofibers [8] were introduced to prepare polymer nanocomposites [4]. The discovery of graphene with its compounds and its ability to disperse well in different polymer matrices created a new branch of polymer nanocomposites. Graphene is a thin atomic monolayer arranged in a two-dimensional plane with SP2 carbon atoms like a honeycomb structure. Different forms [9] of carbon with different dimensions are made from graphene [6]. For example, graphite (a three-dimensional form of carbon) consists of graphene sheets that are stuck together and have a distance of about 37.3°A. The dimensionless form of carbon called fullerene[10] is spherical and can be considered as a dream that it can be made by wrapping graphene sheets. Another one-dimensional form of carbon is carbon nanotubes, which can be made by tubing and tapering graphene sheets. In fact, these other forms of carbon are not synthesized from graphene.