MATERIALS | REINFORCEMENTS
materials in North America, including novel glass products as well as carbon. Gershon says that the anisotropic shrinkage in finished parts often brought about by incorporation of glass fibres into compounds can be corrected with the use of glass flakes such as the Flekaand Fineflake products, which are also distributed by Dreyplas in Europe. Fleka and Fineflake products are manufactured by NSG Group, which is among the world’s largest glass manufacturers. “When used by themselves or in combination with glass fibre, they reduce shrinkage with more balance between the transverse direction and the machine direction in the moulded part,” she says. “Glass flakes significantly reduce warpage in the finished part, yet still maintain almost all the tensile and flexural properties of glass fibre filled parts,” according to Gershon. “Historically, mineral fillers are often added to glass fibre reinforced com- pounds to minimise warpage, but this leads to a loss in mechanical properties. With glass flake, the need to make this trade-off between mechanical proper- ties and part warpage and shrinkage is eliminated.” NSG glass flakes for thermoplastic compound-
ing are small — just 0.7-5.0 microns thick and around 160-600 microns average diameter — and this can make them difficult to feed in to a com- pounding extruder. However, NSG has developed a technology that adds a temporary binder to the flakes so that they form 1mm diameter agglomera- tions, or granules, which are much easier to feed. “Once these granules are exposed to the tempera- tures in the barrel, the binder goes away, and the small flakes remain to provide their reinforcing properties,” Gershon says. NSG offers various grades of flake with different
particle sizes and glass sizings, depending upon the performance needs of the application and the polymer being modified. Fleka flakes (typically 1-5 microns thick and 160-600 micron average diameter) are said to provide the best mechanical
Figure 1: Spider chart comparing performance of a PA66/20% carbon fibre compound using NPS carbon fibre grade CFUW with proprietary urethane sizing against a traditional urethane-sized carbon fibre alternative Source: Dreytek/Dreyplas
properties. Fineflake flakes (typically 0.7 microns thick and 160 microns average diameter) provide a smoother surface in finished parts.
Flake benefits According to Gershon, a further benefit of the Fineflake product is its ability to increase weld-line strength. “Since the flakes are so thin, they cross over and span the weld to provide additional strength,” she says, adding that this is something that many other reinforcements are unable to do. Fleka and Fineflake glass flakes also provide a
wear resistant surface to injection moulded parts and to extruded film and sheet, as well as creating less wear and abrasion of equipment and tooling than glass fibres. “Interestingly, Fleka and Fineflake glass flakes are also used to provide a liquid or gas barrier to moulded or extruded parts, since the glass flakes can align to form a tortuous barrier that substantially reduces the rate of gas or liquid permeation,” Gerson adds.
NeoGraf partnership with First Graphene
NeoGraf Solutions, which specialises in development and manufacturing of high-quality natural and synthetic graphite sheets and powders, signed an exclusive technology partnership with First Graphene Limited, a leading Australian supplier of high-perfor- mance graphene products, in March this year.
Under the 10-year deal, Neograf 34 COMPOUNDING WORLD | June 2022
will sell First Graphene’s PureGraph products under its Graf-X graphene brand in the US, where it is already well established. Neograf has commit- ted to take a minimum of two tonnes of the PureGraph product in year one, scaling to 10 tonnes by year four. NeoGraf’s graphene products enhance mechanical strength, electrical conductivity, thermal
properties, and barrier performance of thermosets and thermoplastics. The graphene materials are said to increase the toughness of plastics by up to 2.5 times without a significant weight increase, while a loading as small as 0.5wt% is said to increase tensile strength by 15% or more. �
https://neograf.com/ �
https://firstgraphene.net/
www.compoundingworld.com
�
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