Wednesday, 2 September 2015

Tinting Epoxy Resin with Toner Powder to Maintain Strength and Stop Discolouration

Building complex projects with composite materials often involves the use of specialist glues, either for strength or athletic reasons.

 


Other uses for tinting or colouring epoxy resins are for the potting of electrical components or cable strain relief , the latter I will describe as the example in this guide...


Whilst building any project, I realised from past experience, that two part epoxy can discolour yellow which, is a sign of the breakdown in the structure of the glue.  I gave the issue some thought and the idea of mixing the epoxy with toner would both colour and help protect the bond from ultra violet light, this being one of  the main causes of discolouration and breakdown. Whilst I could have used an expensive epoxy with UV protection, I couldn't beat a £1 syringe epoxy and free toner! 

So what goes into toner powder?


Toner is made up of  different combinations of  elements, mixed very precisely.

The main ingredients are, in no particular order:

A: Plastic

Plastic powder when heated will aid with adhesion to the paper and to seal the print

B: Iron Oxide (more on this later) Or Carbon

Iron oxide powders act as a carrier for the other powders and are attracted by positive and negative charges during the printing process.

C: Colouring Pigment

Such as cyan, magenta, yellow, and black.


Precautions...

               Toner is not particularly good for you! so take the precautions you feel comfortable with such as wearing gloves and a dust mask. Also exposing your supply of toner to contaminates and humidity is not good for the toner or the laser printer. So, I would advise extracting a small amount - in a vessel such as a bottle cap. The toner can then be resealed out of harms way. The last thing you want is a cloud of toner settling in the carpet or in your lungs after it gets knocked of your workbench. The toner will be perfectly safe to handle, as long as it doesn't become airborne. 

Mixing the materials...


      Only a very small amount of toner is required for the tinting. Too much could compromise the strength or setting time of the epoxy, a sample mix is advised.
           


 The normal two parts of epoxy are mixed in the usual manner.


The applied amount shown below, is more than enough to give a dense black tint to the epoxy.


The toner is mixed in thoroughly...


Application...

Make sure all parts are ready for the treatment before hand...


Using the stirrer the mix can be applied across the header.


Initially the epoxy will run, keep the part rotating to avoid a drip and give an even finish.


Know when to stop pushing the epoxy with the applicator!



Sanity check.

You may have noted at the start of the article, that one of the materials used to produce toner powder is iron oxide ( iron and oxygen.) sometimes carbon. At this point alarm bells might be ringing, carbon, iron and an electrical connection can not be good. With everything bonded together, with resin, no electrical resistance can be measured.


Leave to fully cure.



Here is a low profile Micro USB header, made for the Olympus footpedal modfication. A robust right angled header could also have been easily made.


Whilst strain relief and potting of components are one uses for this method, it can be put to use as with my initial intention, for bonding or glueing  surfaces of a similar colour, with no sign of glue or yellowing over time.


In the below picture masking tape was used to protect the finished edge from the epoxy. Before fully curing a sharp knife can be used to slice the excess glue from the joint.


 Remember toner is not always black! coloured toner can be mixed for many varied combinations.