Mold Release For EPDM Thermoset Application 1

[GrumpyPlasticBastard]

I mold an electrical insulator, six at a time. The machine is an injection mold machine designed for rubber thermoset molding.

Material is a gray EPDM compound, our mold is running at 375 degrees.

Tried many different release sprays... most just bake to the mold and cause issues. Some give release but only last one cycle. That's expensive.

I cannot change the machine mold material or process at this point... what other options are out there for release agents for this application.

 

[GrahamBennett]

Schill & Seilacher markets a wide range of mould release agents and internal lubricants. Have a chat with their technical people.

 

[Compositepro]

There are many mold release companies. It is mostly trade secret art. It sounds like you are looking for a semi-permanent release that can be applied to hot molds. One of the most important things is initial mold preparation. Clean the surface so the release can cure onto the mold surface properly and then apply three or four coats by following the supplier's instructions. Every time I've been rushed and tried to get away with one coat on a fresh surface I have had problems with release.

Hysol Freecote is common in composite molding. Stoner does mainly rubber releases.

 

[GrumpyPlasticBastard]

I requested samples from both suppliers.

Also: I requested samples from suppliers past and present. I am going to set up an experiment:

Solvent, water, dry, liquid base consisting of Z-S, Teflon, B-N, and "other" release agents. Going to run a batch over the weekend and take notes via spreadsheet as to which agents give the best and worst results then take my results to a company that can formulate a custom "flavor."

That will end up being our answer... I just have to narrow down some basic requirements other than "cheapness."

In this regard I am blessed, my boss realizes not it's not a matter of getting a gallon of some "shit" from IMS and ignoring the operator.

 

[jwm6934]

Diamond Kote and Crystal from Franklynn Industries works well with rubber molding.

Factors influencing mold release performance
A. Type of compound (rubber, urethane, composite) being molded
1. Curing mechanism
a. Sulfur
b. Peroxide
2. Hardness of the rubber

B. Composition of mold
1. Steel, Stainless, Aluminum, Chrome, Epoxy, FRP, etc…

C. Complexity of mold
1. Flat, curves, deep draw areas, negative angles
2. How does the mold open up?
3. How is the part extracted from the mold? Ejected, dragged, etc…

D. Cleanliness of the mold

 

[GrumpyPlasticBastard]

I am a thermoplastic-bastard by trade, decade and a half as a setup man doing first-piece and new mold trials.

Rubber is similar but it is different enough that I am challenged by my new job.

While I got ya'll paying attention, can anyone suggest a good book or books on EPDM, rubber technology in general and compression and injection molding of rubber?

 

[jwm6934]

There are three books I use regularly, which have chapters dedicated to EPDM. The Vanderbilt Rubber Handbook (RT Vanderbilt Company), Basic Rubber Technology (Baranwal and Stephens) and Rubber Technology (Reinhold). These aren't specific to EPDM, but they all contain a fair amount of imformation on the polymer. I would also suggest you look at the Rubber Division ACS web site (

http://www.rubber.org)

and check out their online store. They offer a number of publications that may be useful to you. Hope this helps and good luck.

 

[GrahamBennett]

Lanxess has a good (but limited to their product range) on-line rubber technology handbook here:

http://techcenter.lanxess.com/ruc/emea/docs/manual.htm

There is a section on EP and EPDM rubbers (look under Buna EP).