additives feature | Functional fillers
3M’s glass bubbles can be used in plastics to reduce weight and improve a range of properties
glass fibres if these are part of the formulation. High channel-depth conveying elements (OD/ID of 1.75) in downstream processing can help attain a high survival rate, notes 3M. Glass bubbles are typically used in conjunction with
glass fibre to preserve tensile strength, modulus and stiffness. For less efficient reinforcement materials, such as talc, they can replace a large portion of the material on an equal volume basis, explains Amos. Glass bubbles used to partially replace talc or other platey minerals result in a good balance of reinforce- ment and dimensional stability; the high aspect ratio platey mineral adds reinforcement, and the 1:1 aspect ratio spherical glass bubbles bring dimensional stability because they do not orient in the melt. These property improvements and the lower density
of glass bubbles are key for applications in areas such as transportation and aerospace, while newer markets such as electronics and shoe soles are also taking advantage of the lightweighting aspects, says Amos. Some 3D printing materials processed for short-run aerospace parts can use glass bubbles for lightweighting. 3M is currently building a new manufacturing facility
for glass bubbles in Clinton, Tennessee, USA, which is expected to commence production in the third quarter of 2016. 3M has commercialized surface-treated glass bubbles for epoxy resins, unsaturated polyester (SMC and BMC), and base-sensitive polymers like PC, and is continuing to commercialize other coated bubble grades.
Nanoclay news A decade ago, there was much hype about nanocom- posites based on separating bundles of bentonite or montmorillonite clay mineral platelets and dispersing them in a polymer. These nano-sized platelets held the promise of improving properties at low additive levels. The hype has now died down, but nanoclays are being used commercially, particularly for their flame retardant, barrier, and dimensional stability properties.
58 COMPOUNDING WORLD | August 2015
“Flame retardation is leading the way for nanoclay
applications,” says Tie Lan, general manager of Nanocor, which is a Minerals Technologies Company. “Char forming, anti-dripping, and reduction of heat and smoke release during burning are the most significant benefits,” he explains. For example, nanoclay is used with ATH or MDH to
improve flame retardant properties. Nanoclays also work well in combination with bromine-containing flame retardants. For example, Nanocor’s Charex 44PSS nanoclay can be used to replace a portion of ATO in a bromine-containing flame retardant formulation. Nanoclays improve barrier properties because their high aspect ratio creates a tortuous path that blocks flow of gases. Only low levels are needed, which helps retain overall physical properties. A nanoclay with an aspect ratio of 200 only requires 1% by volume (about 2% by weight) to cut permeability in half, compared to a clay with an aspect ratio of 20, which requires 9% by volume, according to Lan. He adds that commercial barrier enhancing applications include extending shelf-life for food packaging and controlled release of active ingredients. In automotive applications, nanoclays can be used to
improve dimensional stability (heat deflection tempera- ture or coefficient of thermal expansion, CTE) and to increase stiffness without loss of flexibility in PP or TPOs. A Nanomer-TPO exhibits a higher surface gloss than a talc-TPO, Lan noted in the ACCE presentation. Noble Polymers, for example, used nanoclay in a PP nanocomposite for an automotive console, and found that it eliminated warpage, reduced weight, improved scratch and mar resistance, and improved thermal characteristics. One of the early challenges for nanoclays was
exfoliating the platelets during compounding so that they are totally separated. However, researchers eventu- ally concluded that full exfoliation was not needed. “Dispersion and distribution, plus interaction of the nanoclay, are the most important issues,” explains Lan.
www.compoundingworld.com
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