APPLICATION TECHNOLOGY

Pushing the limits with instant adhesives

Instant adhesives are characterised by their ability to create high-strength bonds with very good aging resistance, even in the smallest gaps. However, choosing the right product is essential to get the best results, which is why Loctite offers its users a broad range of industry-proven cyanoacrylates.

considerably extend the spectrum of possible applications. Powerful solutions are available even for difficult-to-bond plastics such as PP, PE, POM, PTFE or silicones. Loctite points out that each of its different product categories

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has been optimised as appropriate for the applications involved. For example, the elastomer-modified cyanoacrylates from Loctite offer good impact and shock resistance and are therefore used to bond loudspeaker parts, the housings for rechargeable batteries in power drills, or similar applications. Flexible products, on the other hand, can reliably withstand

repeated twisting or bending of the bonded materials and are therefore suitable for bonding the plastic sheaths on the metal temples of flexible-frame sunglasses or for attaching rubber profiles to refrigerator doors made of painted metal. For transparent parts requiring very good optical performance,

hilst multipurpose products already deliver very good results for bonding a variety of different material combinations, specialty products have additional specifically engineered characteristics which

light-curing cyanoacrylates will be the best choice. These adhesives cure within seconds when exposed to UV or visible light. And they remain clear and transparent after curing. The scope of applications in

industrial manufacturing processes has been broadened by the recent addition of the first gap-filling cyanoacrylate Loctite 3090. “Since conventional cyanoacrylates mostly have very low

viscosity, they were only used to join close-fitting parts. This was a drawback that severely restricted their range of uses. With Loctite 3090, Henkel has vastly broadened the application range of instant adhesives, offering an unmatched capability to fill gaps up to 5mm wide. The new instant adhesive is suitable for almost all materials, including metals, most plastics, rubber and ceramics. Even porous substrates such as wood, paper and cork can be reliably bonded with it.”

Brass versus stainless steel T

he thermal characteristic of brass enables the inserts to heat up and cool down quickly during the installation process into moulded plastic parts. For those inserts that are installed with heat or ultrasonics, the fact that the brass

insert heats up quickly translates into faster installation time. From a quality perspective, the fact that brass cools quickly

means that immediately after the heat is removed from the insert the plastic will start to coagulate which will secure the insert in position and prevent it from “floating” within the hole. Compare this to a steel insert that takes significantly more time to heat up - the time it takes to melt the plastic and the total installation time is longer. When it comes to machining, brass is much easier to cut

than most ferrous materials. Whereas brass and stainless steel generally cost about the same per pound as a raw material, it’s the significant increase in manufacturing time for stainless steel that drives up costs. Though brass is an excellent choice for most components,

there are instances where stainless steel may be required. For example, brass and stainless steel are both corrosion resistant, yet each will react differently to various corrosive agents. Brass is an excellent material for use in most industrial and agricultural applications and typically offers the lowest cost solution. It offers much better thermal conductivity than carbon or austenitic stainless steel and is much more efficient material to machine than stainless steel. Many varieties of stainless steel are available, although 300

Spirol Industries Ltd, based in Corby, Northamptonshire, manufactures all of its standard inserts from brass. Below it explains the benefits of using brass for inserts compared to other materials.

series, or austenitic stainless steel, is most comparable to brass in terms of those insert applications where stainless is commonly used. It is critical to understand that the properties of stainless steel vary dramatically from one alloy or family to the next, and it is difficult to make general statements regarding performance. Stainless steel is more difficult to machine than brass and

cycle times are much longer which increases cost significantly. Tool life is also severely limited which further increases cost. Austenitic stainless steel provides higher service temperatures than brass. However, it is important to note that the service temperature of the assembly is usually limited by the heat deflection temperature of the plastic host.

120 Fastener + Fixing Magazine • Issue 68 March 2011