Determination of Mechanical Properties of Epoxy Composite Materials Reinforced with Silicate Nanofillers Using Digital Image Correlation (DIC)

Combined Thermomechanical Effect of Graphene Oxide and Montmorillonite on Biobased Epoxy Network Formation for Coatings

Epoxy nanocomposites derived from linseed oil, reinforced with graphene oxide (GO) and montmorillonite (MMT) nanostructures, were synthesized. The nanohybrids were developed by enriching the structure of MMT and GO with primary amines through a common and simplified method, which implies physical interactions promoted by ultrasonic processing energy. The influence of the new nanoreinforcing agents along with neat ones on the overall properties of the biobased epoxy materials for coating applications was assessed. Interface formation through surface compatibility was contained by the lower values of activation energy calculated from differential scanning calorimetry (DSC) curves, along with a consistent 70% increase in the cross-linking density when amine-modified MMT was used. Thermomechanical characteristics of the biobased epoxy nanocomposites were explained through the interaction of the functional groups over the curing process of epoxidized linseed oil (ELO), giving a 15 °C higher Tg value increase. Furthermore, the low surface energy values suggested an intrinsic antibacterial activity, as proved by a significant decrease of CFU against Staphylococcus aureus bacterial strains on the 0.25% reinforced coatings.

Reinforced Epoxy Binder Modified with Borpolymer

Polymer binders based on epoxy resins have unique properties that contribute to their use in many composite industries. The potential of using epoxy binders is due to their high elasticity and strength characteristics, thermal and chemical resistance, and resistance to climatic aging. This is the reason for the existing practical interest in modifying the composition of epoxy binders and understanding the strengthening mechanisms in order to form reinforced composite materials with a required set of properties based on them. This article presents the results of a study of the process of dissolving the modifying additive of polymethylene-p-triphenyl ether of boric acid in the components of an epoxyanhydride binder applicable to the production of fibrous composite materials. The temperature and time conditions for the dissolution of polymethylene-p-triphenyl ether of boric acid in anhydride-type isomethyltetrahydrophthalic anhydride hardeners are presented. It has been established that the complete dissolution of the borpolymer-modifying additive in iso-MTHPA occurs at a temperature of 55 ± 2 °C for 20 h. The effect of the modifying additive of polymethylene-p-triphenyl ether of boric acid on the strength properties and structure of the epoxyanhydride binder has been studied. Increases in transverse bending strength up to 190 MPa, elastic modulus up to 3200 MPa, tensile strength up to 0.8 MPa, and impact strength (Charpy) up to 5.1 kJ/m² are observed when the content of the borpolymer-modifying additive in the composition of the epoxy binder is 0.50 mass. %.

Experimental Study on the Characterization of Orientation of Polyester Short Fibers in Rubber Composites by an X-ray Three-Dimensional Microscope

Polyester-short-fiber-reinforced rubber composites have been detected by an X-ray three-dimensional microscope, and then the three-dimensional reconstruction of the image has been carried out to characterize the orientation of polyester short fibers in the composites for the first time. Based on the summary of three traditional methods and mechanisms of characterizing the orientation of polyester short fibers by the numerical parameter method, the direct test method, and the indirect test method, the method and mechanism of the X-ray three-dimensional microscope applied to the orientation characterization of polyester short fibers have been studied. The combination of the center point and threshold segmentation methods has been used to distinguish which fiber section belongs to the same fiber, and the identification of the whole short fiber in different slice images has been realized for the first time. Moreover, Avizo software has been used to realize the three-dimensional reconstruction of a polyester short fiber scanning image. The obtained data have been integrated and the orientation angle and orientation degree have been quantitatively characterized for the first time. This has filled the key technical problem of quantitative characterization of the orientation angle and orientation degree of polyester fibers. The image has been verified by 3Dmed software, and furthermore, the accuracy of the three-dimensional reconstruction results has been verified.