Preparation of hybrid nanocomposites based on resolgraphene carbon fibers and checking their mechanical and thermal properties

Master's Thesis in Polymer Industry Engineering

Abstract

Phenolic resins have excellent dimensional, thermal, chemical and corrosion resistance. Also, the fugitives produced during the thermal degradation of this resin have low toxicity and, in addition, have high charring. Phenolic resins have found many applications in areas such as internal parts of war planes, structures used in marine platforms, flame retardant plastics, and carbon/carbon composites due to having the mentioned favorable properties. In this research, phenolic resin samples of Resol reinforced with carbon fibers and graphene nanoparticles were prepared. Different amounts of graphene (0.5%, 1%, 2% and 3%) were dispersed in a 50% solution by weight of phenolic resin and ethanol by ultrasonic waves for 10 minutes with 60% power of the device. After that, hybrid composites containing 50% by weight of carbon fibers were prepared by manual layering method, and the samples were baked at 160 ?C, 120 bar pressure by hot press. The morphology, thermal properties and mechanical properties of the prepared nanocomposites were investigated by XRD, FTIR, SEM, TEM, DSC, TGA and three point bending tests and the results were compared. By adding 1% by weight of graphene to the resulting composites, the modulus and flexural strength of the samples increased by 19.5% (38.2GPa) and 8.7% (471MPa), respectively. Also, the shear strength of the sample containing 1% graphene by weight increased by 23% compared to the pure sample. The thermal resistance of phenolic resin/graphene composites showed a significant increase compared to pure resin. For example, in the sample containing 1% by weight of graphene, the observed increase in T5%, T10% and Td,max indices was 12, 30 and 5 ?C, respectively. The results of the DSC test showed that the addition of graphene nanoparticles decreases the enthalpy of the baking reaction and also shifts the exothermic peak to higher temperatures. This can indicate the spatial hindrance effect of graphene sheets during the baking reaction, which is caused by the high surface area of ??graphene sheets. 

Keyword: Phenolic resin, graphene, carbon fibers, interlayer cutting, mechanical properties

1-  Chapter 1

1-1- Introduction

In the last decade, the development of new polymer nanocomposites has grown significantly. has had 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 the role of graphene sheets on curing, thermal resistance, morphology and chemical structure of phenolic resin, as well as the adhesion of the resin to the fibers and the resulting mechanical properties.

1-3- Background of the research

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. Graphite itself is a natural substance that was obtained in 1555 in Browdale, England, but the first time it was used was perhaps 4000 years ago. Single-walled carbon nanotubes were first synthesized in 1991 after the discovery of fullerenes in 1985. Of course, the first published reports for the synthesis and production of graphene date back to 1970. Separation of a graphene monolayer has been achieved for the first time in 2004 through micromechanical exfoliation of graphite. The exceptional properties of single-layer graphene, such as Young's modulus TPa1 and strength GPa130, have made it the strongest material whose properties have been measured so far. Its thermal and electrical conductivity are 5000 W/mK and 6000 S/cm, respectively, which are higher than the values ??reported for carbon nanotubes. Also, the surface area of ??graphene sheets is very high (2630 m2/g). These excellent properties have caused graphene sheets to have the ability to improve the mechanical, electrical and thermal properties of polymers. Therefore, in the last decade, the investigation of this amazing material and its nanocomposites has attracted the attention of many researchers and scientists, so that from 2004 to 2009, about 3000 ISI articles have been published in the field of graphene-based nanocomposites [7].