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TECHNOLOGY | NANOCOMPOSITES


tremendous potential of nanocomposites,” says Richard Marshall, CEO of TenasiTech in Boston, MA, US. His company has developed anti-mar/ scratch additives based on nanoclay technology for various polymers, including acrylics, polyamides, and polyesters. “From a strategic point of view, in recent years, polymer producers have released fewer and fewer new polymers in the market. Rather, they extend resin performance by making small variations to polymer chemistry, or develop co-polymers based on their existing feedstock. This provides opportu- nity for nanocomposites in several ways,” he says. “First, innovation lies more and more with compounders or OEMs, who are more open to composite material solutions to differentiate their


offering to end-users and have greater flexibility to deliver such solutions. Second, new co-polymers can suffer from other performance deficiencies which need fixing through additives; such as scratching in our case,” Marshall explains. “If we have one criticism, it is that the nanocom- posite community can be prone to the whims of ‘materials fashion!’ We have seen this with nano- clays, which were highly publicised in academic and trade circles early on but fell out of favour when other materials became in vogue. Our philosophy is to complete the work with customers required to extract value from these materials, value we know is there to be exploited.” Compounding into polymers is usually not trivial for nanomaterials, Marshall says, noting that “a great


Tips for processing nanoparticles


“Processing of nanoparticles with ther- moplastic matrices is always a challenge,” says Raquel Llorens, a compounding specialist in the Compounding Department at Spanish plastics technology institute AIMP- LAS. “The extraordinary high specific surface of nanoparticles compared with conventional reinforced fibres induce great attractive forces between the nanoparticles themselves, in different levels of aggregation, producing agglomerates (from 0.5 microns to 200 microns). Depending


on the particle geometry, we can find different types of agglomerates: bunches for spherical particles, stacks for sheet particles, and balls for fibrillar structures.” Llroens identifies several key challenges to dispersion of graphene materials in thermoplastics. “Thermo- plastics are high viscosity fluids in the melt form; graphene sheets can be broken by the effects of high shear and are very easy to bend and roll; there is great variability in the chemical behaviour of polymers, from highly


polar to totally non-polar; dispersion methods must be able to scale industrially in a simple and inexpensive way; polymers are very large mol- ecules with limited infiltration power between graphene sheets,” she says. AIMPLAS research has identified


three key technologies for dispersing nanomaterials in polymer matrices: dispersion in liquids; “In-situ” polymer- isation; and melt mixing (as used in conventional compounding). Table 1 spells out the pros and cons of each. � www.aimplas.es


Table 1: Advantages and disadvantages of different techniques for dispersing graphene nanoparticles in thermoplastic compounds


METHODS “In-situ”


Advantages Good dispersion of graphene in polymerization polymer matrices


Strong interaction between graphene and polymer matrix


Dispersion in liquids


Simple route to disperse graphene in polymer matrices


Good dispersion of graphene in polymer matrices


Melt mixing


(compounding process)


More commercial and scalable


The use of surfactants can affect the properties of polymers


The elimination of the solvent can cause the


aggregation of the graphene sheets Not friendly to the environment


Poor dispersion of graphene compared with other methods


More compatible with industrial practices Can cause winding or breakage by high shear Environmentally friendly


Needs large equipment Suitable for mass production Source: Aimplas 28 COMPOUNDING WORLD | December 2018 www.compoundingworld.com Disadvantages


Increase in viscosity that hinders handling and maximum load level


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