| Frequently Asked Questions
(FAQ) |
Mixing and Measuring Adhesives |
|
Re-stir all products before
weighing or dispensing. Carefully weigh out resins and hardeners or powders
and
binders into separate containers before mixing. (Use a minimum mix of 25
grams to insure a homogenous mixture.) Mix both parts of the adhesive system
thoroughly before using.
Improper measuring or mixing can
cause: materials not to cure, soft spots, air voids on the surface, sticky
surfaces, softening at elevated temperatures, changes in chemical or
electrical resistance.� |
Bonding Dissimilar Materials |
| Select an adhesive with a
thermal expansion coefficient that closely matches the materials to be
bonded. When possible select a flexible epoxy. Clean dirt, oils, greases and
mechanically roughen the surfaces prior to bonding. Cure the materials at
room temperature for 4-16 hours and at 250�F for two hours. � |
Recommended Bond Line Thickness for Adhesive
Bonding |
| For standard epoxy and
ceramic adhesives a bond line thickness of 5-8 mils (0.005" - 0.008") will
produce excellent results. for Cotronics' non-sag putties (epoxy or ceramic)
bonds of 0.020" or more can be used. To form a thick layer, or section, apply
putty in several layers curing between each application. |
Joint Design and Bond Strength |
| Butt joints are usually the
weakest, inserted joints (tongue and groove, rod in a tube) are considered
to be mechanically reinforced and the strongest type of joint design.
For repairing difficult applications use a metal or ceramic cloth buried in
the glue line for additional reinforcing. |
Bonding to Teflon, Nylon, Polyolefin and
Similar Plastics |
| Specific surface treatments
and/or etching are required for bonding these plastics. Cotronics offers
flexible (4538) and activated epoxies (7050) that form strong adhesive bonds to many of
these difficult-to-bond materials. |
Preventing Flow of an Adhesive From a Joint |
| Select an adhesive with
high viscosity or with thixotropic properties and use just enough adhesive
to completely fill the gap between the two surfaces to be bonded. |
Thinning Adhesives for Application |
| Adhesives sometimes require
thinning in order to ease flow, create a thinner bond line or facilitate
encapsulation. Epoxy formulations can be thinned with mild heat or epoxy
thinner 105RT. Ceramic adhesives can be thinned with the corresponding
thinner for the particular adhesive. Thinning ceramic adhesives should be
done at a minimum to prevent cracking or weakening of the material.
|
Removing Bubbles in Potting Materials |
| You can reduce the amount
of entrapped air by warming epoxies prior to application or by vacuum
degassing. (Apply pressure of 29 inHg for 2 minutes, repeat 2 more times if
needed). |
Working with Electrically or Thermally
Conductive Adhesives |
| Electrically and Thermally
conductive adhesives will provide optimum results after a post cure for 2
hours at 250�F. Electrically conductive materials are also available in
flexible versions to accommodate bonding substrates with different thermal
expansions. |
Cracking in Ceramic Adhesives and Castable
Ceramics |
| Cracked and weak castings,
encapsulations, or adhesive bonds can occur when using ceramic materials if
excess activator or additional water has been added to the uncured mixtures.
Check the mix ratio that was used when mixing the materials. Castable
Ceramics will achieve optimum strength after heat treating. |
Accelerating Cure Times |
| The best way to shorten the
cure cycle is the raise the temperature. Typically most systems can be
quickly cured at 250�F. Check the data sheet or the product label for
specific curing directions for the material you wish to use. |
Modifying Existing Formulations |
| Cotronics
can adjust formulations to provide variables as viscosity, gel times, curing
characteristics as well as lap shear strength, peel strength, flexibility,
chemical stability, heat resistance, impact strength, color, etc. |
Special Packaging for Production Applications |
| Cotronics can supply
materials in pre-measured units and in bulk quantities to facilitate the use
of these systems in any production facility or field application. |
