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Question: What is the definition of a structural adhesive? (January 2011)

Answer (Adhesives & Sealants Committee):

An adhesive is a material that is applied to the surfaces of articles to join them by an adhesive bonding process. An adhesive is a substance capable of forming bonds to each of the two parts when the final object consists of two sections that are bonded together. A feature of adhesives is the relatively small quantities that are required compared to the weight of the final object.

Structural adhesive bonding is bonding for applications in which the adherends (the objects being bonded) may experience large stresses up to their yield point. Structural adhesive bonds must be capable of transmitting stress without loss of integrity within design limits.

Bonds must also be durable throughout the useful service life of a part, which may be years. A structural bond has been defined as having a shear strength greater than 7 MPa (1015 psi) in addition to significant resistance to aging.

A simple definition would be that when given standard conditions, 77deg F., 50% relative humidity and 1 atmosphere the weakest of two joined substrates will fail.


Question: I was hoping you might be able to recommend some textbooks to me.  I am switching careers (from the management of commercial construction projects), and am interested in broadly learning about resins, how resins can be applied in a commercial settings, and the various manufacturing processes that are used with resins.  I’m interested in the specific manufacturing process of potting and encapsulating and casting.

There are a few different companies that make interesting architectural panels out of resins – www.veritasideas.com and www.3-form.com and www.lumicor.com.  I would like to manufacture panels similar to those produced by Veritas.  I would also like to understand more about resins and their limitations – and how I can make other types of artistic and architectural products from resins. 

I’m hoping to self educate myself by reading a variety of textbooks and speaking with others in the industry.  Could you recommend some various textbooks that would give me a broad overview of resins and the various manufacturing processes associated with resins?  Thanks for your help. (April 2010)

Answer (Potting, Encapsulation, Electrical Committee):

Encapsulation of Electronic Devices and Components, Edward R. Salmon, Marcel Dekker Inc. 1987 is an excellent primer for a number of thermosetting resins.

In order to learn about all types of resins associated with polymeric resins used in the adhesive and sealants industry, we would recommend the Handbook of adhesives and sealants by Ed Petrie.

If the requirement is specific to epoxy resins, then we would recommend the Handbook of epoxy resins by Henry Lee.  Both of these books will give an overview of potting & encapsulation process.

Also subscribe to Composites Technology magazine as well as High Performance Composites.  These are both great references and are free.


Question (from a student): How to get epoxy resin with highly conductivity in asian market, especially in Indonesia. I am attempt to make a bipolar plate for fuel cell. (April, 2010)

Answer (Potting, Encapsulation, Electrical Committee): When talking about conductive epoxy resins, there are primarily 2 types and they are thermally conductive and electrically conductive epoxy resins.  

In order to make thermally conductive epoxy resin systems, fillers of various kinds have been used traditionally.  These fillers include Aluminum oxide, Aluminum Nitride, Boron Nitride etc.  The level of filler to be used will depend on the thermal conductivity requirement.  Filler loading and thermal conductivity are directly proportional to each other, with higher loading providing higher thermal conductivity numbers.

Similar methods could be followed for epoxy resins that are electrically conductive epoxy resins.  Metal and carbon fibers have been effectively used to improve electrical conductivity of epoxy resins.  Carbon Black is the simplest of these powders that could effectively improve the electrical property without much increase in thermal conductivity. Carbon Nanotubes, Graphene, silver coated fibers have been used extensively to improve the electrical properties.


 

Past Questions (The answers to these questions are available to TRFA Members on the members-only website):

  • What are the commonly used VOC exempt solvents (by EPA Method 24) in epoxies and urethanes? (March, 2010)
  • What is a typical decomposition temperature range for a room temperature cure rigid epoxy? If this question is too broad, what is it for a 100% reactive (no diluents, plasticizers or fillers) rigid epoxy? (March, 2010)
  • I am trying to get a definition of advanced polymer composites -- what resins and fibers are involved and what markets they serve. (Feb. 2010) 
  • We are repeatedly asked about the life span of a structural laminate.  Is there an appropriate accelerated test method that will help predict the life span? (Sept. 2009)
  • Could you provide expert advice on pros vs cons of various methods for the determination of chemical resistance of a composite laminate or thermoset polymer? (Sept 2009)
  • Where can I find information regarding compatibility between Thermoset and Thermo plastics used in the manufacturing of finished components? (Sept. 2009)

 


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