Woodworking & Joinery

The Assembly (Rigid) Market can be defined rather broadly and includes the following types of applications:

  • Appliances (such as washing machines, dishwashers, refrigerator/freezers)
  • Furniture (made from wood, metallic or plastic construction)
  • Housewares (including small appliances such as toaster ovens, fish aquariums, kitchen and bath accessories)
  • Lamination (as in laminated countertops)
  • Machinery (including the motors which power them)
  • Millwork, Doors, Cabinetry (made from wood construction)
  • Sandwich Panels (insulated panels used in home and building construction)

Bonding Wood

In woodwork, and in particular in the furniture-making industry, polyvinyl acetate dispersion adhesives have long superseded the carpentry adhesives based on animal proteins that were used thousand of years ago. Condensation resins (urea, melamine, phenolic and resorcinol-formaldehyde resins) have made possible the development of new wood-based materials such as plywood, chipboard and laminated composites (resorcinol/ phenol-formaldehyde resins) for building construc­tion.

Melamine-formaldehyde resins are used in conjunction with special papers for manufacturing decorative boards for laminating wood for furniture manufacture. Polyurethane (PUR) adhesives that cure by exposure to moisture are currently of growing importance for the manu­facture of chipboard, due to the fact that they represent formaldehyde-free alternatives to the aforementioned polycondensation resins. In addi­tion, they are being increasingly used for bonding wooden construction elements. As with adhesives in many areas of technology, wood adhesives are also tending to become 100% systems -they com­bine simple application with rapid curing. Hot melts have proved particularly useful as adhesives for assembly work and for bonding decorative edging. The application of PUR hot melts, which cure via the influence of moisture, is very much on the increase for the structural bonding of wood and for joining wood with a host of other materials. This type of adhesive involves two different curing mechanisms: the solidification of the hotmelt on cooling means that the components are rapidly affixed. The chemical curing which then follows, involving the crosslinking of molecules, leads to high-strength bonds.

The Ocean on Your Table

What was all the rage in the mansions of 19th century? Fishbowls and aquariums. Technically though, this was quite a messy hobby. Candles underneath the tank provided heating and lighting, yet most of the fish did not outlive winter. The aquariums were sealed using window putty. However this material aged quickly, becoming brittle and eventually leaking. Since the late 1960s, aquariums have therefore been sealed using silicone sealant adhesives.

Thanks to silicone, proud owners of goldfish can contentedly watch their finned friends from all angles. But this has not always been the case. The first aquarium was introduced to the public at large in 1851 at the London World-Exhibition. The windows were held in place with a cast iron frame. Until the late 1960s, most aquariums were built based on this principle. The windows were fastened to a metal frame using window putty. The product, made from 85% calcium carbonate and 15% linseed oil varnish, is a sealant that has been in use since the 1700s. While the product is definitely watertight at the beginning, over time it becomes brittle as linseed oil oxidizes in the air, thus leading to leaks.

The disadvantages of a framed aquarium, however, were not limited to window putty, which began to crumble over time and was rendered useless. The metal frame also meant an obstruction of the line-of-sight. When gazing at the fish, nothing should remind the beholder that the exotic underwater world behind the window is artificial. The only alternative was aquariums made completely of glass.Yet there was a catch again: although these designs were frameless, they accommodated a maximum of 20 liters (about 5.3 US gallons).

Fortunately, late in the 1960s the first silicone sealants provided the solution to the problem. Using the invisible material, the aquarium’s windows were fixed into place and effectively tightened at the same time.

Now why are silicones perfectly suited for aquarium design? They are water resistant and adhere firmly to glass. As is the case with window putty, they harden in the air, more precisely by atmospheric moisture. The silicone atoms, together with oxygen atoms, form molecular chains. The remaining free external atoms of the silicone are saturated by residual hydrocarbon. Compared to window putty, silicones keep their elasticity and remain watertight even under extreme conditions and for a long period of time. What is more, they do not yellow and the unusual, underwater fish paradise remains unclouded by the silicone strips.

Additional Resources

Bonding with the Industry (Article courtesy ASI magazine)

The process of taking thin slices of wood and gluing them together to increase strength and stability dates back to the tombs of ancient Egypt, with archeologists discovering traces of laminated wood in the resting places of pharaohs. The Engineered Wood Association suggests on its website that the Chinese began the practice for furniture production more than 1,000 years ago, with Russians advancing the craft during the 17th and 18th centuries. The association notes, however, that it was a small Oregon-based wooden box manufacturer that essentially launched the plywood industry in 1905 by showing its wares at the World’s Fair held in Portland that year. Learn more

Untraditional Use of Adhesives in Structural Metal Bonding (Article courtesy ASI magazine)

In many industries, manufacturers of metal components are turning to structural adhesives to replace or augment rivets, bolts, welding and other traditional fastening methods in their assembly processes. Adhesives can improve product performance and aesthetics, reduce overall assembly time, and lower production costs. Advances in structural-adhesive technology have dramatically expanded the scope of potential metal-bonding applications. Until recently, most structural adhesives would lose strength over time on galvanized steel. New patented adhesive technology provides long-term durability on galvanized substrates. Structural adhesives are also excellent alternatives for bonding metal-to-metal, metal-to-plastic and metal-to-composites. Learn more.