Interphase characterization and modeling of tensile modulus in epoxy/silica nanocomposites

Abstract

The incorporation of second dispersed particulate phases in a polymer matrix enhances its mechanical properties. Because of the high surface to volume ratio of nanoparticles, the molecular structure of the matrix is altered at the nanoparticle/matrix interface and the volume of this perturbed region could be significant. These improved properties are produced by the interfacial interaction of the nanometric domains. In this research, epoxy matrix modified with three different sizes of nanosilica (12, 20, and 40 nm) and the effect of the interphase characteristics on the tensile properties of nanocomposites was investigated. At first, the theoretical values of the elastic modulus using a twophase mathematical model compared with the experimental data obtained from the nanocomposite samples and values between 8 and 10 nm were estimated for the interphase thickness. Afterward, considering the three-phase model, it takes into account that three different regions for interphase volume fraction, including single particles, polymer trapping, and agglomerated nanoparticles, and an equation for evaluation of interphase volume fraction are defined. Also, the interphase tensile modulus was considered continuously changing from the properties of nanoparticle to the polymer matrix properties. Finally, the overall tensile modulus of nanocomposites, which considers different key parameters including nanoparticle size, values for the interphase thickness (h), and interphase tensile modulus (E i), were calculated. The results were compared with the experimental ones of other studies and a good agreement was found. The smallest value of h as 6 nm for samples containing 12-nm diameter nanosilica and highest value of h as 8 nm for samples containing 40-nm diameter nanosilica is reported.

An efficient nanoscale representative volume element simulation including graded interphase for tensile behavior of epoxy/silica nanocomposites

“…Also, the interphase elastic modulus is assumed E i = 1.5 E m . In our recent study, 25 by comparing experimental data with theoretical models, the value of 6 nm for the interphase thickness of the epoxy polymer reinforced with 6 nm nanoparticles was predicted. Also, the interphase zone surrounding the nanoparticle is chosen stiffer than the matrix and the assumption made about the interphase modulus is in the range of similar articles 4,23 .…”

“…The variety of the molecular structure within the interphase zone was expected not to be uniform 22,25 . It is assumed that the elastic modulus and Poisson's ratio of the polymer chain in interphase region change from the properties of the nanoparticle surface grafted chain to the bulk polymer chain continuously, as shown in Figure 4(a,b).…”

“…Moreover, r p and h is the radius of nanoparticles and the interphase thickness, respectively. So, the variations of the elastic modulus and Poisson's ratio of the interphase layer as a function of distance to the nanoparticle surface were considered by using Equations () and () 25 : where r is the distance aligned interphase thickness and is variable in the range of r p ≤ r ≤ r p + h and ß is the coefficient of interfacial characteristics between the matrix and reinforcement.…”

Effect of fumed silica and halloysite nanoparticles on the microstructure, mechanical, and fracture properties of thermoplastic polyolefin elastomer toughened polypropylene

“…To improve the tensile strength and modulus of blend polymers, a nanoparticle was usually used to improve the balance of strength, stiffness, and toughness of the composite. [10][11][12][13][14] It is well accepted that the effect of nanoparticles on the mechanical performance of compounds depends entirely on their properties, shapes, sizes, and concentrations. [15,16] The cheapest and most available tubular and spherical nanoparticles are halloysite (HNT) and fumed silica (FS), respectively.…”

Effects of nano reinforcing/matrix interaction on chemical, thermal and mechanical properties of epoxy nanocomposites

“…The effects of nanoparticle-matrix interface properties and the curing behavior of the matrix should be covered well to interpret the results of all these studies. 10,[14][15][16] In recent years, the research on CNT and ceramic nanoparticle filled epoxy nanocomposites had increased rapidly to improve epoxy polymers' thermal and mechanical properties. The properties of CNTs such as high aspect ratio (1,000-10,000), 17 low densities, high stiffness, and tensile stress (Young's mod-ulus1 TPa, 60 GPa) have made them attractive nanofillers in the production of epoxy nanocomposites.…”