Adhesives Improve Quality of Life

 

The paste we utilize in everyday life to carry out minor repair jobs has long been extensively employed by industry. This adhesive does still generally remain concealed between two or more substrates, out of sight to consumers.

The contemporary method of foodstuff retailing and self-service with its ready-to-eat meals, frozen goods and instant foods would be unimaginable with no adhesives for manufacturing water-resistant packaging materials, such as plastic-coated films, or for hermetically sealing packaging.

 

 

 

Bottle labeling is used now to demonstrate the extent to which apparently uncomplicated “everyday” applications of bonding are in realism “high-tech” solutions: Gluing paper together is child’s play, using either a stick of adhesive or a fluid paper adhesive. The intensity is determined by the tear strength of the paper surface and is consequently limited. There is though something special about bonding labels to bottles: The high working speeds of the mechanized filling machinery mean that the glue must have high initial tack and the label must be cleanly taken from a magazine. After being rolled onto the typically damp bottle, the tag must neither slip nor ripple. And if the bottle still has to remain in rainwater or if water condenses on the tag, then the labels must remain attached. On the other hand, when the empty bottle is returned for reuse at a later date, the tag must be able to be easily detached during the rinsing stage before being refilled. A special casein adhesive is able to meet all these requirements: It bonds quickly, is resistant to water and is soluble in the alkaline washing liquid.

Medical Industry

Glues are used extensively in the medical world, from simple plasters to advanced medical applications. Too, adhesives are integral to the making of paper tissues and nappies, allow tablets to be protected from the effects of moisture and allow wounds to be dressed. Transdermal patches, such as the nicotine patch, allow a controlled release of nicotine into the bloodstream to help smokers quit.

The next time you spot a cobbler at work in a quick-repair shop, watch how he glues on a novel rubber heel. He removes the old heel from the shoe using a pair of pliers, roughens the fusion area and so removes any residues of old adhesive. He then applies a medium viscosity adhesive around the edge of the novel heel, over a breadth of about 1.4 inch. He then presses the heel alongside the shoe and presses it for a short time in a press. The bond is now intact and the edge can be cleaned up. The reactive adhesive that allows him to work so fast is a cyanoacrylate, also normally called a superglue. When applied as a slim film, this adhesive cures very rapidly in contact with moisture or traces of alkaline substances. For the cobbler’s effort, it is not necessary to apply the adhesive to the entire joining area. This would in any case be problematic when it was time for the shoes to be repaired yet again, because the very strong bond would not be able to be mechanically detached without damaging the shoes. In contrast, leather and rubber shoe soles are usually bonded on by means of a contact adhesive based on polychlorobutadiene. Not like cyanoacrylates this forms a flexible-elastic film. Both joining areas are covered with the contact adhesive. After leaving in air for about 15 minutes, the sole is pressed against the shoe. Once again here, the high initial force of the bond immediately after joining is beneficial.

The above examples have described bonding effects based on adhesion and cohesion mechanisms. In the next example, another feature is considered, that is the capability of the adhesive to dissolve the surface of the substrate.

The aircraft manufacturing industry provided the important know-how urge for modern bonding technology. The basic need for weight saving was the driving force for new design and construction methods. In contemporary Airbus aircraft, for example, about 30% of all components are fixed using bonding technology.

In the car manufacturing industry, typical joining techniques are these days used in combination with bonding. In some areas bonding has entirely replaced the typical techniques. The increased demand put on engine seals has resulted in bonding technology being used widely in modern engines, for example for cylinder head seals, in a variety of components for cooling water provision and for the oil sump. Adhesives are also increas-ingly being used as structural materials. Contemporary cars contain up to 40 feet (150 m) of bonded joints in the body construction. In addition, bonded front and back windscreens increase the rigidity of the bodies and result in weight reduction. A customized thick-film bonding system dampens vibrations and moreover improves the heat insulation exclusive of usage of supplementary materials as is necessary in conventional designs. Optimized designs with enhanced driving performance, reduced mass and lower susceptibility to corrosion result in considerable energy savings.

Bonding know-how plays a unique role for light weight constructions with integrated functions. This means of construction attempts to make products having added functions, without adding up extra mechanism. For example, correctly designed bonded joints between two metals, panes of glass or wooden slats can act as a hinge.

 

In the area of electronics, the classic joining technique of soldering is being increasingly replaced by bonding, in order for example to connect highly integrated components with each other in a hassle-free way and without the need to use excessive heat.

Limitations of Adhesives

 

Just like other sophisticated technologies, the relevance of glues in a production environment necessitates that unique processing procedures are adopted. In broad-spectrum, thorough assessment of the quality of a bond by non-destructive testing is not achievable. Bonding – like welding and brazing/ soldering – is therefore considered to be a so-called unique method. While using bonding in a production environment, suitably high production class is consequently required, as the product class is not tested. Degradation mechanisms have to be taken into explanation when taking into account the long-term strength of bonded joints. Degradation can decrease the intensity of bonds but is usually identified to be manageable. One restriction forced by nature on the use of bonding know-how must however not be forgotten: A obvious shortcoming of bonding technology compared to other joining techniques is that the consequential bonds merely have limited stability to high temperature owing to the actuality that adhesives are natural compounds.