The Role of Nanoparticle Layer Separation in the Finite Deformation Response of Layered Polyurethane-Clay Nanocomposites

Abstract

Nanoscale control of structure in polymer nanocomposites is critical for their performance but has been difficult to investigate systematically due to the lack of a suitable experimental model. In this work, we investigated the role of nanoparticle layer separation in the finite deformation response of layered polyurethane-(PU-) montmorillonite (MTM) nanocomposites. A series of multilayered nanocomposites was manufactured, with alternating PU and MTM nanolayers, using a layer-by-layer manufacturing technique. The systematic variation in MTM nanoparticle volume fraction was achieved by varying the thickness of the PU nanolayer and therefore the MTM layer separation. Traditional polymer nanocomposite blending techniques result in a wide variation in nanoparticle separation for a given nanocomposite. In this investigation, we controlled the MTM nanoparticle layer separation, which allowed us to examine its effect on the nanocomposite response over a broad range in nanoparticle volume fraction. The PU-MTM nanocomposites demonstrated an increasing yield strength and stiffness with increased MTM volume fraction or reduced nanoparticle layer separation. A transition from ductile to brittle behavior in the stress-strain constitutive response was observed at a high volume fraction of MTM nanoparticles. We demonstrate that a critical nanoparticle separation exists, below which brittle behavior dominates the response of PU-MTM nanocomposites.

Deoxyguanosine Phosphate Mediated Sacrificial Bonds Promote Synergistic Mechanical Properties in Nacre-Mimetic Nanocomposites

“…[17][18][19] The nacre-like complexity is difficult to transfer into synthetic materials to reproduce the mechanical behavior, as the highly ordered self-assembled structure and supramolecular interactions need to be mimicked at several length scales. Nacre has been mimicked by sequential deposition processes, [20][21][22][23][24][25] which are, however, not scalable and which are prohibitive when macroscale sample thicknesses are aimed. Ice-templating and sintering allows tough nacremimics but suffer from a multistep process.…”

Mechanical, thermal and accelerated weathering studies of bio‐based polyurethane/clay nanocomposites coatings

“…It was observed that storage modulus was found to increase with the increase of nanoclay content. [26,27] The value of tan delta found to decrease with the increase of nanoclay content. The hydroxyl groups present on the surfaces of 30B-clay layers may interact with the hard segments of the polyurethane lead to enhance the modulus of the nanocomposites.…”

Bioinspired Hierarchical Composites

“…Using this strategy, nature is able to grow functionally graded structures that are capable of minimizing mechanical stresses at the interfaces between materials with a large mismatch in mechanical properties (Genin et al 2009;Harrington et al 2010;Yao et al 2010). Unlike in nature, the strategy of using mechanical gradients is far less exploited in polymer-based artificial composites, mainly because the level of reinforcement achieved in synthetic systems comprising a common organic phase is often limited by the increasing concentration of processing defects and confinement of the polymer matrix at high volume fraction of reinforcing elements (Bonderer et al 2008, Kaushik et al 2009Bonderer et al 2010). Developing processing techniques that allow for a tunable reinforcement of a common polymer matrix within a wide range of values can potentially lead to graded polymer-based composites that further extend the functionality of currently available metal/ceramic graded materials (Mortensen and Suresh 1995).…”