Polyester Resin Pen Problem

[Aphidrider]

I just turned my first Polyester Resin pen. I cast the resin with a 7mm tube glued into a carbon fiber sleeve. The turning went great and the parts looked perfect....then I tried to set the pen parts in the tube.

As I was setting the chassis into its tube, the resin "broke away" from the carbon fiber sleeve. The resin did not break or crack it just separated from the sleeve so you could see the silvery separation from the sleeve and the resin.

Any ideas and how to prevent this? The only thing I can think of is I was using some replacement 7mm tubes and not the exact ones that came with the pen kit itself. Is it possible all 7mm tubes are not created equal and I was trying to fit a chassis into a tube that was too small, causing the tube to expand and break away from the resin?

Any ideas or help would be greatly appreciated.

 

[Displaced Canadian]

Not a subject that I'm an expert in. I do know that some brittle materials can crack and break when the parts are pushed in. Sometimes it helps to ream the ends a little larger and use locktite to hold the parts in.

 

[bruce119]

OK...I've have seen this many times...there are a few causes...the silvery effect you see is separation from the resin probably to the carbon fiber. I have not done much Carbon Fiber (C.B.), it can be a bit tricky, I will give some tips that mite help???

My big question is how did you prepare the tube and adhere the C.F. to it.
Did you paint the tube, did you scuff the tube for better adhesion or just slip the C.B. over it.


There are different methods for C.F. (library) But the big thing I think to get in mind is that in the end you want good adhesion all the way through. Some will slip the C.B. over the tube then soak with CA, some slip over tube then saturate with epoxy, and then I would try something like slipping the C.B. over the tube and with a nitrite glove squeeze and massage P.R. into the C.F. saturating it to the tube, then put your blank in a mold and cast under pressure, The big PIA I had with C.F. is air being trapped.


Now there's much more then that but it mite give you some ideas....


Also another BIG reason for P.R. separation is when pressing in the parts. You don't want them real tight or go in askew. If the tube expands too much you risk separation.


Another note, How much MEKP did you use, If you followed the instructions on the can you used WAY too much. Use 3-4 drops per once, It will take about 12 hrs for the P.R. to cure. Slower cure = a more flexible, workable, finished product. Fast cure = a very brittle glass like unforgiving finished product.


Hope I gave you some ideas...
Good Luck...have fun

 

[Aphidrider]

Thank you, your responses do give me some things to consider. I did scuff the tube slightly and then slid it over the carbon fiber. To adhere the carbon to the tube, I drizzled CA down the length of the tube while rotating the tube, but I definitely did not dunk it in CA which could have ensured a much better adherence to the tube.

I also did use 6 drops of MEKP/ounce, so I will try using less. It was a rainy day when I cast the tube and after 24 hours I still needed to pop it in the oven for 30 minutes to completely harden the resin. It was tacky after 24 hours but solid below the mold line.

Thanks again for the responses. They will help my future attempts for sure.

 

[bruce119]

Thank you, your responses do give me some things to consider. I did scuff the tube slightly and then slid it over the carbon fiber. To adhere the carbon to the tube, I drizzled CA down the length of the tube while rotating the tube, but I definitely did not dunk it in CA which could have ensured a much better adherence to the tube.

I also did use 6 drops of MEKP/ounce, so I will try using less. It was a rainy day when I cast the tube and after 24 hours I still needed to pop it in the oven for 30 minutes to completely harden the resin. It was tacky after 24 hours but solid below the mold line.

Thanks again for the responses. They will help my future attempts for sure.

This is were P.R. get a little tricky/complicated humidity and temperature defiantly effect the end product. I try to cast in an environmentally controlled (A.C./Heat) room. Ideally between 75-80 deg. never below 68 or above 85. Ambient temp defiantly effects cure times. Longer is better..surface tack is normal, It mite feel tacky to the touch but you shouldn't be able to push a pop stick into the cast. I don't (or avoid) put in oven if you do don't go over 150 HEAT-not good. What I do to finish the cure, surface tack is put the molds out in the open air/sun for about 3-4 hours and that does the trick.
Good Luck