Preparation of PA6/vermiculite composites by reactive extrusion method and determination of their thermal, morphological and mechanical properties

The use of polymeric materials is increasing day by day thanks to their superior properties such as high corrosion resistance, low density, easy shaping and recyclability. However, the properties sought in many applications are difficult to find in a polymer alone. For this reason, the preparation of polymer composites is a very effective and common method to impart different properties to polymers. Composites are prepared by adding other components such as fiber, ceramic, metal and clay to the polymer. Many properties of the prepared composites such as thermal, mechanical, dielectric, electronic and magnetic are investigated. According to their determined properties, polymer composites are used in many applications such as biomedical, optics, defense industry, electromagnetic shielding, sensors, building and construction, batteries, electronic components. Polyamide 6 (PA6) is used in many sectors such as aviation, automotive and white goods, thanks to its superior mechanical properties and high service temperature properties. However, since they are petroleum derivatives like many polymers, their resistance to thermal degradation is low. These aspects limit its usage areas. For this reason, studies on increasing the resistance of PA6 to thermal degradation have increased recently. Additionally, research has been conducted on various PA6 composites to improve their use on a sectoral basis. Recently, the use of clay has become preferred in terms of improving the mechanical properties of PA6 due to its light weight and affordable cost compared to market conditions. Among these clays, vermiculite, in addition to its properties such as low density, low cost and thermal stability, has also been discovered in recent years for its fire retardant properties. In this thesis study, polymer/clay composites were prepared by adding 5 and 10% vermiculite by mass in order to improve the thermal and mechanical properties of PA6 and also to reduce its carbon footprint and cost. In the composites, 3-glycidyloxypropyl)trimethoxysilane (GPTMS) agent was used to provide chemical bonding between vermiculite and PA6. In addition, composites containing only clay and PA6 were also prepared to investigate the effect of the presence of silane agent. Firstly, silane agent/clay mixtures were prepared by spraying method, and then the final mixture prepared with the addition of PA6 was prepared by the melt mixing method using a twin screw extruder. In the melt mixing stage, reactive extrusion process was carried out by covalently binding the silane agent to the clay surfaces from the methoxysilane parts and to PA6 from the epoxy part. From the ATR-FTIR spectra of the composites, it was seen that characteristic peaks from both components appeared in the vermuculite-GPTMS mixture prepared by the pre-extrusion spraying method, thus it was understood that the mixture was prepared successfully. In the spectra of the composites, it was observed that the characteristic peak intensity of the Si-O-Si vibration increased with the clay ratio, as expected. While the characteristic peaks of PA6 and vermiculite were seen from the XRD results of the composites, it was understood that the peaks of vermiculite increased with the amount in the composite. From the SEM images of the samples, evidence of chemical bonding between vermiculite and PA6 in the composites containing the silane agent was clearly seen. From the DSC results, it was concluded that there was no significant change in the melting temperatures of PA6 and composites, and that the amount of clay and the use of silane agent increased the crystallinity. From the tensile tests, it was determined that the elastic modulus values increased with the clay ratio and did not change much with the presence of silane agent, and the tensile strength increased with the clay ratio and silane agent. It was determined that the elongation at break values increased approximately 7 times in the sample containing silane agent and 5% clay compared to neat PA6. It was evaluated that this increase was due to the chemical bonding between PA6 and vermiculite in the presence of silane agent. Thus, by preparing PA6/vermiculite composites, raw materials that can be used in many sectors have been developed, with improved mechanical properties, reduced carbon footprint and cost.