Adhesives, Mechanical Engineering


Adhesives are a substance able of holding materials together. A joint is formed among two solids is called adherends with a thin layer of adhesive among them. Mainly adhesives are made via some kind of plastic either in emulsions, solutions, liquid, powder or paste form that is allowed to solidify and harden within curing process. Adhesives have distinction of making joints in between similar and dissimilar materials. Plastic to glass and or glass to metal and metal wood can be joined via adhesives even if the strength of these joints is much less than those joints as welds. Though, the adhesive joints are effectively strong in shear and tension but weak against peeling or cleavage. This may also be maintain in sense that the strength of polymeric adhesive joint is considerably impaired because of presence of dust, grease, oil or rust. The surfaces to be joined should be as soft as possible whether only thin layer of adhesive will be necessary. Thinner the adhesive layer stronger will be the joint. The thin layers are void creep and free less. The adhesive film is generally 0.1 millimeter thick.

The adhesives are made from elastomeric, thermosetting and thermoplastic polymers. Thermoplastic adhesives are prone to loss of strength as like their soft at high temperatures. Temperature close to 100oC may not be allowed for such adhesives. Thermosetting adhesives may be employed at slightly higher temperatures. These adhesives do not soften on high temperature but until lose strength. Elastomeric adhesives are fewer sensitive to temperature even if they are similar to thermoplastic adhesives. Improved results have been acquired by blending various resins in several proportions. That type of adhesive blends is called as adhesive alloys.

The adhesives that are strong bonding and less creeping are consider as structural adhesive. Epoxy based adhesives available like liquid, solid or past and epoxy blends along with phenolics, polysulfide or nylon resins are the examples of structural adhesives. Phenolic adhesives were illustrated to be utilized between wood veneer for their resistance to water and mould growth in Section of Natural Polymers. For joining wood melamine formaldehyde mixed along with urea formaldehyde is preferably employed. This adhesive is usually available in powder form and is reconstituted by mixing along with water before application.

The adhesives based upon elastomers and thermoplastics are weaker than those based upon thermosetting plastics. They are mostly called non-structural adhesives. A lot of these, particularly elastomeric adhesives, and contain good peel strength and impact strength. Polyurethane polyster and silicone are not many bases of such adhesives.

In addition to synthetic or polymeric adhesives declared above, natural adhesives as like: starch, soya flour, animal products and dextrin and inorganic adhesives as like: sodium magnesium and silicate oxychloride are also employed. Both these classes of adhesives are however, less in strength as compared to synthetic organic adhesives.

Posted Date: 2/27/2013 5:52:18 AM | Location : United States

Related Discussions:- Adhesives, Assignment Help, Ask Question on Adhesives, Get Answer, Expert's Help, Adhesives Discussions

Write discussion on Adhesives
Your posts are moderated
Related Questions
Basic Concep: Proper care and maintenance are essential for trouble free operation and optimum performance of the motorcycle. A quality service at regular intervals ensures that e

How CAD system communicate with control system The concept of a universal data exchange system is depicted in figure. In this figure, it is shown how various CAD systems commun

Explain the function of the foundation The function of the foundation is to ensure that the loads on the super structure are transmitted to the soil below the foundation withou

Clutch cable model: Ensure the cables fitted is of the respective model and not interchanged with other model. Also ensure that the cable is genuine.

calculate the head required

Determine the width and depth of the beam: A timber beam of rectangular section is only supported over a span of 5 m. It carries an uniformly distributed load of 15 kN/m over

Welding transformer The resistance welding transformers step down the line tune of 2 to 20 V. The primary is connected to the line supply and is made from edge bent copper stri

Evaluate power transmitted by belt.  Sol: Let T 1  = Tension in tight side of the belt T 2 = Tension in slack side of the belt V = Velocity of belt in m/sec.  = Π

It is estimated that the average number of surface defects in 20 square meter of paper produced by process is 3.what is probability of finding number more than 2 defects in 40 squa