FASTENING & JOINING FEATURE LEVERAGING ADVANTAGES OF HYBRID ADHESIVE INNOVATIONS
The reason behind the growing popularity of cyanoacrylates in the engineering arena is that they are extremely versatile and easy to use, can perform multi-substrate bonding and deliver fixture times of a few seconds in most applications. In addition, they provide fast assembly
solutions for materials including plastics, elastomers and metals and cure at room temperature to achieve very high bond strengths; in most cases the substrate will fail before the adhesive joint breaks. The product is kept liquid inside the bottle by an acidic stabiliser. When dispensed the moisture on the surface of the substrate neutralises the stabiliser and cure is initiated. The best results are obtained in atmospheres with 40-60% humidity. Full cure will be achieved with less humidity but a little more time is required. With a typical bond line thickness of just
0.1mm cyanoacrylates offer initial cure in seconds. The joint will achieve about 50% of its total strength within 60 seconds and 100% in 12-24 hours. Joints set into a rigid thermoplastic with an operating temperature range from -50°C to +80- 90°C, although some offer up to +120°C. Most engineering plastics can be joined
including ABS, LCP (liquid crystal polymer), PBT, polycarbonate, PMMA (acrylic), nylon (polyamide) and polysulfone; nitrile, butyl
gap filling properties include LOCTITE 3090, a two-part product capable of filling gaps up to 5mm. Toughened instant adhesives feature rubber particles in an adhesive matrix that act as crack arrestors. Although normal cyanoacrylates can
and neoprene rubbers. Cyanoacrylates are suitable for wood, leather, fabrics, steel and aluminium. For plastics and rubbers where the surface energy is below 33mN/m such as PEEK, POM (acetal/Delrin), polyethylene, polypropylene, silicone rubber, Viton and PTFE (Teflon) a bond can still be achieved by ensuring that the surface is properly wetted. Cyanoacrylates are not suitable for bonding glass. Despite the resounding attributes of
cyanoacrylates, technology developments in this area continue. For instance, development programmes at Henkel include those targeting acidic/porous bonding, toughened grades and flexible grades such as LOCTITE 4092 for medical industry applications. Furthermore, low odour products and cyanoacrylates with
Attributes of LOCTITE 4090 include high impact resistance, temperature resistance up to 150°C, high moisture resistance and gap filling up to 5mm
support high tensile loads, under a peel load joints can break relatively easily due to crack propagation. For applications where peel strength is required, toughened adhesives such as LOCTITE 480 are required. While cure time is slower (around 60 seconds) such products offer good adhesion between metals or metal and rubber. Epoxies represent a viable alternative to instant adhesives. These typically comprise a resin and a hardener which are mixed together manually or automatically to achieve a cured product. Cure times range from 5-10 minutes to
4 hours. As a rule of thumb, if an epoxy is required with good durability, adhesion and toughness then a slow-curing epoxy is often the best choice. The properties of epoxies vary greatly in terms of flexibility/ toughness, temperature resistance, viscosity, colour, cure speed and conductivity (electrical and thermal).
Henkel T: 01442 278000
www.henkel.com
More than 33,000 standard parts and components for mechanical and system engineering
www.norelem.co.uk
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