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Colloidal Polymer Composites: Are Nano-Fillers Always Better for Improving Mechanical Properties?

Makepeace, David, Locatelli, P., Lindsay, C., Adams, James and Keddie, Joseph (2018) Colloidal Polymer Composites: Are Nano-Fillers Always Better for Improving Mechanical Properties? Journal of Colloid and Interface Science.

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Abstract

Hypothesis

Colloidal polymer composites, in which polymer particles are blended with a filler, are widely used in applications including pharmaceuticals, crop protection, inks, and protective coatings. It is generally found that the presence of hard particulate fillers will increase the elastic modulus of a polymer colloid composite. However, the influence of the size of the filler particle on the large-strain deformation and fracture and on the viscoelastic characteristics, including creep, is not well explored. We hypothesize that the size ratio of the filler to the colloidal polymer will play a critical role in determining the properties of the composite.

Experiments

Colloidal composites were prepared by blending soft polymer colloids (as a binder) with calcium carbonate fillers having four different sizes, spanning from 70 nm to 4.5 μm. There is no bonding between the filler and matrix in the composites. The large-strain deformation, linear viscoelasticity, and creep were determined for each filler size for increasing the filler volume fractions (ϕCC). Weibull statistics were used to analyze the distributions of strains at failure.

Findings

We find that the inclusion of nano-fillers leads to brittle fracture at a lower ϕCC than when μm-size fillers are used. The data interpretation is supported by Weibull analysis. However, for a given ϕCC, the storage modulus is higher in the rubbery regime, and the creep resistance is higher when nanoparticles are used. Using scanning electron microscopy to support our arguments, we show that the properties of colloidal composites are correlated with their microstructure, which can be altered through control of the filler:polymer particle size ratio. Hard nanoparticles pack efficiently around larger particles to provide reinforcement (manifested as a higher storage modulus and greater creep resistance), but they also introduce weak points that lead to brittleness.

Item Type: Article
Divisions : Faculty of Engineering and Physical Sciences > Physics
Authors :
NameEmailORCID
Makepeace, Davidd.makepeace@surrey.ac.uk
Locatelli, P.
Lindsay, C.
Adams, JamesJ.Adams@surrey.ac.uk
Keddie, JosephJ.Keddie@surrey.ac.uk
Date : 22 March 2018
Identification Number : 10.1016/j.jcis.2018.03.067
Copyright Disclaimer : © 2018 Elsevier Inc. All rights reserved.
Uncontrolled Keywords : latex; Nanoparticles; Creep; Fracture; Viscoelasticity; Composites; Nanocomposite; Nanofiller; Calcium carbonate; Plasticizer; Weibull statistics; Critical pigment volume concentration (CPVC)
Depositing User : Clive Harris
Date Deposited : 23 Mar 2018 12:06
Last Modified : 23 Mar 2018 12:06
URI: http://epubs.surrey.ac.uk/id/eprint/846074

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