Today’s consumers are radically different than previous generations. Consumers now make more time for leisure and are far more mobile. Items that used to sit on a table and be hard-wired to the wall, like a phone or TV, are now stuffed into a pocket or a purse and travel far from home.
Within the home, today’s consumer is making new demands of conventional products, like moving the television from the living room to the bathroom or kitchen, exposing the TV to whole new levels of moisture, chemicals, and environmental impacts.
As a result, companies are seeing new and different demands for today’s consumer products. This relentless demand for greater durability without added weight is triggering a shift in the product design and manufacturing world: a growing use of adhesives and sealants to bond advanced materials.
This trend may be news to some manufacturers, but lab tests show that the latest generation of these adhesives has been engineered to more than earn its “toughened” moniker.
Toughened epoxies now play a critical role in a wide range of consumer products, providing a range of gains in product and cost performance over mechanical fasteners, welds, and rivets:
- Reduced weight. Adhesive weighs less than rivets or screws
- Lower production costs. The labor costs associated with a skilled welder are higher than the cost of a worker applying adhesive.
- Improved appearance. Visible rivets are replaced by near-invisible epoxy.
- Ability to bond dissimilar substrate. For example, welding even relatively similar surfaces such as aluminum and steel does not work well.
- Improved durability. Vibration, shock and impact are absorbed by an adhesive.
- Better load distribution. This feature comes into play on impact. Because the bond covers the entire substrate instead of being concentrated at a point (e.g., a rivet site), the load is distributed over a greater area and the product is more durable.
Engineers and product designers accustomed to traditional methods of bonding may have questions about durability. But a closer look at the science behind toughened epoxy shows how it is, in fact, possible to create an adhesive that achieves bonds with tensile strength up to 5,000 psi or higher.
The science of toughening epoxies incorporates rubbery material within the epoxy matrix to absorb and disperse the energy of dynamic shock and impact mitigating stress so as to reduce and eliminate failure.
The science of absorbing energy and mitigating stress also improves the durability of both the adhesive and the finished product by improving the overall fatigue resistance of both.
Unlike mechanical fasteners, where the fastener’s physical properties and manufacturing dimensions, along with the substrate’s thickness and properties, will influence bond joint success, an adhesive bond can actual bond at the molecular as well as the mechanical level (with appropriate surface preparation).
Adhesive bonding joins parts through physical and chemical means, creating physical, chemical, and electrochemical interactions between the bulk substrate and adhesive. This modified structure along with the adhesive’s cohesive properties can create permanent and powerful bonds, rivaling, and in many cases exceeding, those of mechanical fastening methods.
From airplane wings to mountain bikes
The daily wear and tear of everyday life is hard enough on consumer products, but the demands don’t stop there. For instance, what do an airplane wing, mountain bike and composite driveshaft have in common? The answer – they must all offer extremely high shear and peel strength, and they are all examples of products in current use that are held together by toughened epoxy adhesives.
Or think of items that must stand up to extremely high impact, like a golf club driver. According to calculations in this 3M Golf Club Glue- Why it Works video, the average force on the adhesive bond attaching a 200 gram club head is estimated to exceed 3,460 pounds. The reason that these clubs don’t shatter is because of rubber-toughened particles embedded in the 3M adhesive. When stress travels through the adhesive, these particles stop it from cracking.
Using toughened adhesives makes it possible to design beautiful, reliable, and useful products that can withstand the challenges of today’s mobile, high-impact lifestyle. The shift to adopting toughened epoxies is a major move toward continued light weighting and durability – and a major way to keep consumer products on the move.
Filed Under: Materials • advanced