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EPOXY

Epoxy is a thermosetting polymer formed from reaction of an epoxide “resin” with polyamine “hardener”. Epoxy has a wide range of applications that include fiber reinforced plastic materials and general purpose adhesives. When these two are combined they formed a secure bond. The process of polymerization is called “curing”, and can be controlled through temperature and choice of resin and hardener compounds; the process can take minutes to hours. Some formulations benefit from heating during the cure period, whereas others simply require time and ambient temperatures.


The most common packaging types for epoxies are dual pouch clip systems, dual cartridges, and syringes. The mixed ratios of 1:1, 2:1, 4:1, and 10:1 are generally used with these packaging types. Some epoxies are pre-mixed / frozen to stop the curing process and then heated to room temperature to be used for the desired applications.

Substrate Preparation :

The strength and durability of bonded joint are dependent on proper pre-treatment of substrates to be bonded. At the very least surfaces to be joined should be cleaned with a good degreasing agent such as Acetone or Trichloroethylene in order to remove all traces of oil, grease, rust, dust, etc. from the surface. The best and most durable joints are obtained by either mechanical abrading (Sand Blasting) or by chemical etching (pickling) the degreased surfaces. Mechanical abrading shall be followed by a second degreasing treatment.

APPLICATION OF ADHESIVE
Apply a thin layer of the mixture on the pretreated and dry surfaces to be joined, using a spatula. Soon after the application of the adhesive, the components are to be positioned /aligned and clamped together. Even contact pressure throughout is sufficient to achieve good bond. Allow the bond to cure. This curing process is room temperature dependent i.e. higher the temperature faster will be the process. Normally at 30°C the handling strength is achieved within 4 hours. Full cure will be attained in 18-24 hours.

CURING TIME versus TEMPERATURE

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  • Curing time depends on the weather temperature.

  • Higher temperature results in faster curing.

  • Care should be taken while subjecting the component to higher temperature (eg. Plastic· part may get damaged) .

DO’S AND DONT’S

  • ​Even though it is advised to mix Resin & Hardener until uniform colour is attained, it is beneficial to mix for at least 2-3 minutes thoroughly. Correct R/H proportion & thorough mixing is the secret of consistent and optimum bond strength.  Do not mix large quantity at a time.

  • Never add extra hardener to expedite the curing process, instead take the help of heat to achieve this mix.  Never dilute R/H mix with solvents to lower the viscosity.

  • Replace the respective caps of Resin & Hardener containers whenever they are not in use. Hardener tends to form skin if exposed to air for long time.  Wipe off the excess oozed quantity from the bond area, when the adhesive is wet.

  • Do not keep the R/H mix near heat source such as hotplate.

  • Method by weighing is more appropriate. If mixing by volume, never pour resin• & hardener over one another. Pour equal quantity side by side. This way judgement of volume is good.  Do not disturb the bond during setting i.e. after the clamping of assembly is over.

Surfaces must be clean, Dry and free oil, wax and paint. Protect work area lightly roughen smooth.Apply in a well ventilated area. Wear Hand Gloves when work and Wash Hand after use.

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