Adhesives, Mechanical Engineering

Adhesives

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
Clutch free play: Check for free play of the clutch lever, it should be within 10-20 mm.

Points of Contraflexure: Assume M 1 , M 2 , . . . and M 6 be the points of contraflexure, where bending moment changes sign. To determine the position of M 2 , let a section

Explain Rake angle - Angles of a drill It is also known as helix angle .It is the angle formed between a plane containing the drill axis and the leading edge of the land. It c

Calculate the angular deflection (in degrees) produced in a solid circular shaft of diameter 12.5mm and length 0.5 m when the shear stress is 25MPa and the shear modulus 70GPa. Wha

Q. Explain the working of Die Casting? In the die casting process the, mould used for a casting is permanent called a die casting. it is shown in figure. It is thus quite diffe

have assignment in FEM calculation and ANSYS are you able to solve this kind of assignment

Friction is Undesirable: A friction is undesirable at the time of ice skating or when the block is lifted or put down on the truck with the help of inclined plane. If friction

Tyre: Different bikes respond differently to different tyres, so it is impossible to make a generic recommendation. It mainly consists of outer cover and inside tube. The tyre tub

Define the Boundary Representation of solids Boundary model or b-rep model is based on the topological notion that a physical object is bounded by a set of faces. These faces a

Develop an EES Code for a Rankine cycle with reheat and with 2 open feedwater heaters.  The cycle is shown below:  Use the following conditions: 1.  700 psi, 850F 2.  500