RUBBER & PLASTICS
MYTH 7. THEY ARE NOT GAP FILLING Most cyanoacrylate adhesives are inherently of a low, runny viscosity, which means they do not work well when there are gaps to be filled, if the parts are porous, or if the bondline orientation means that the adhesive would drip or run out. However, CAs are now available in a range of
different viscosities for gap filling. Born2Bond Repair, Structural, Flex and Ultra all offer high- viscosity formulations for gap filling. The high viscosity ADH9454 CA gel, for example, prevents running on inclined or vertical surfaces during its three to 60 second fixture time, enables gap filling up to 0.5 mm, and minimises the absorption of adhesive into porous substrates to ensure a good bond.
MYTH 8. THEY HAVE POOR MOISTURE AND SOLVENT RESISTANCE This is generally true, and in the past this has limited their use in many industrial applications. Actually, CAs have better resistance to non-polar solvents like IPA; it doesn’t seem logical, but cyanoacrylate adhesives have more chemical resistance to petrol than they do to water. Advances like the hybrid chemistry of Born2Bond Structural now give superior moisture resistance, showing a very small reduction in adhesive strength after 1,000 hours immersion in water, and much improved compatibility with polar solvents.
MYTH 9. THEY ARE NOT STRUCTURAL ADHESIVES To date, CA bond strength has been readily compromised by temperature and moisture/humidity, which has limited their use for load-bearing applications. However, Born2Bond Structural has very high impact resistance (27 KJ/m2
steel after 24h), and
toughness. It develops structural bonding performance to steel, ABS, PVC, phenolic and polycarbonate, amongst other substrates, and features particularly good adhesion to aluminium (lap shear strength 12 MPa). With higher temperature, moisture and solvent resistance, it is a good candidate to test for a structural industrial application.
MYTH 10. THEY STICK YOUR FINGERS TOGETHER FOREVER! More people than would care to admit have accidentally stuck their fingers together with Super Glue - the moisture in our skin is ideal to initiate curing. Luckily, soaking your hands in soap and warm water will loosen the cyanoacrylate enough for you to slowly peel your fingers apart. If this does not work, an acetone-based nail varnish remover should finish the job. If you left the CA untreated, eventually the fats and oils in your skin would remove the glue and unstick your fingers, but we do not recommend you test this out.
Intertronics
www.intertronics.co.uk
Patrick Loock, segment business owner for products and applications at composite tubes and profiles manufacturer Exel Composites, discusses how composites manufactured with thermoplastic functional coatings can allow more control of properties such as friction, adhesion, and finish.
common of the two types, harden through curing, forming heavily cross-linked polymers with insoluble or infusible rigid bonds that will not melt when exposed to heat. While not as common in pultrusion, thermoplastic resins are increasingly being explored. Thermoplastics are branches or chains of monomers that soften when heated and solidify when cooled. This is a reversible process with no chemical bonding, meaning you can re-melt and re-form them as needed and mold them to fit virtually any shape. Thermoplastics that can be used with composites include, but are not limited to, thermoplastic polyurethane (TPU), poly(methyl methacrylate) (PMMA), polyethylene (PE), polyamide (PA) and Polypropylene (PP).
T
ADVANTAGES OF THERMOPLASTIC FUNCTIONAL COATINGS There are advantages in combining a thermoplastic functional coating with a thermoset composite. By extruding thermoplastic functional coatings as a step in the composite’s production, manufacturers can provide additional mechanical properties, such as shock absorption, bond strength between components, grip, and corrosion resistance, as well as add more aesthetic possibilities in profile designs. The thermoplastic coating allows manufacturers to offer wider finish possibilities, so customers can have an expanded range of products with shiny, matte, rubber, or even metallic appearances, allowing seamless integration with existing structures. The metallic looking finish is popular because
UKManufacturing Spring 2023
here are two main categories of resins used when producing composites, thermosetting and thermoplastic. Thermosetting resins, which are the more
composites are often used as replacements for metal parts in existing structures and this allows them to blend in visually. Thermoplastic coatings also offer practical benefits for end users. For example, when thermoplastic coatings are used for telescoping components, the improved friction between the tubes and locks means that the telescope can withstand more force before collapsing. Carbon fibre has extremely good mechanical properties, offering the desired strength and weight, but sometimes it does not have the necessary friction and/or adhesion properties for the application. By coating the carbon fibre composite with a thermoplastic coating, the product can gain the required friction and adhesion properties, as well as additional protection for the composite from environmental factors, such as weather, water, or other damaging circumstances. This could be useful in examples such as marine applications, strata control or tension members. Exel Composites has developed expertise in continuous composite manufacturing processes, such as pultrusion and pull- winding, and provides in-line functional coatings of composites during the manufacturing process, instead of the more typical approach of adding coating post production. This allows customers to take advantage of all the benefits of thermoplastic- coated composites, such as shock absorption and corrosion resistance, while reducing manufacturing complexities. Furthermore, because of the precise
fibre alignments and process controls, pultrusion and pull-winding ensure consistent production quality batch-to- batch and are highly repeatable.
Exel Composites
www.exelcomposites.com
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THERMOPLASTIC FUNCTIONAL COATINGS AND COMPOSITES
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