Formation of nanoparticle aggregates and agglomerates in polymer nanocomposites and their distinct impacts on the mechanical properties

Abstract

In this study, the different effects of nanoparticle aggregates and agglomerates on the mechanical properties of polymer nanocomposites are comprehensively investigated. To this end, a specific strategy, based on the equilibrium between the dispersion and cohesion energies in the mixing stage, is proposed using which the content and size of aggregates/agglomerates can be defined. The aggregated/agglomerated networks are considered to place in constrained volumes (CVs), having co‐continuous morphology. An equivalent box model (EBM), corresponding to the system, is used to predict the tensile modulus of the nanocomposite. Different test results of HDPE nanocomposite samples, containing 1–3 wt.% of surface‐modified silica nanoparticles, prepared by a semi‐industrial single screw extruder, are applied to validate the model. Moreover, other data from the literature are also used to further evaluate the accuracy and capability of the proposed analytical method.

An energy‐based strategy to predict the thickness and content of randomly oriented nanolayers aggregates/agglomerates in thermoplastic polymer nanocomposites: Experimental and analytical approaches

“…The dispersion energy (e d ) should be defined based on the geometrical structure and capabilities of the applied mixer. 17,19 According to Bousmina et al, the shear stress (τ) between equivalent cylinders, representing an internal mixer, is 26…”

“…This challenge directly affects the processibility and physical/mechanical properties of the systems since the formation of nanoparticle clusters decrease the polymer/particle interface area and accordingly alters the impact of the reinforcing phase. [16][17][18] Aggregation implies that the nanoparticles attach via strong bridges, such as covalent bonds, which can be formed during the synthesis or surface modification processes. 16 On the other hand, the attachment between agglomerated nanoparticles is relatively weak and almost only capable to maintain the cluster structure without any significant resistance capabilities against the exerted forces.…”

“…16 On the other hand, the attachment between agglomerated nanoparticles is relatively weak and almost only capable to maintain the cluster structure without any significant resistance capabilities against the exerted forces. 17,19 The formation of both aggregates and agglomerates in polymer nanocomposites is commonly introduced as a drawback that negatively affects the characteristics of the system. However, according to some more sophisticated approaches aggregates may act even better than individual nanoparticles in enhancing the mechanical properties of polymer nanocomposites.…”

“…However, according to some more sophisticated approaches aggregates may act even better than individual nanoparticles in enhancing the mechanical properties of polymer nanocomposites. 16,17 The shape of nanoparticles determines the aggregation/agglomeration mechanism of nanoparticles based on how they can interact and form strong/ weak bonds. 20 For example, the spherical nanoparticle aggregates/agglomerates can have a maximum number of six attaching points with their neighbor nanoparticles while in the case of nanolayers, there is no attachment point but an interface that is responsible for the formation of clusters.…”

“…Another major problem involved with applying different shape nanoparticles in polymer matrices is their aggregation or agglomeration. This challenge directly affects the processibility and physical/mechanical properties of the systems since the formation of nanoparticle clusters decrease the polymer/particle interface area and accordingly alters the impact of the reinforcing phase 16–18 . Aggregation implies that the nanoparticles attach via strong bridges, such as covalent bonds, which can be formed during the synthesis or surface modification processes 16 .…”