MIL-PRF-23377G (Is this good for FIBERGLASS, as a PAINT of PRIMER)?

[designmr]

My question is maybe simple, but I am not a paint expert.

I have HIGH DENSITY PVC FOAM insulation (McMaster Carr 9318K64). Our callout on long running drawings was to POWDER COAT, but this seems wrong. Powder coating FOAM. I am looking at PAINT, does MIL-PRF-23377 cover paint for PVC FOAM? Again, I am no expert and after reading spec, I am still confused if MIL-PRF-23377 will cover this PRIMER and PAINTING of PVC foam.

If paint, I know we would need to PRIMER first, than paint per FED-STD-595.

I hope I didn't confuse anyone.

thank you in advance,

 

[tbuelna]

I would recommend reading the MIL-PRF-23377 spec as a start. MIL-PRF-23377 describes a two-part epoxy primer for application on metal surfaces, or fiberglass surfaces that have been properly prepared.

As for FED-STD-595, it only covers the color of the coating.

 

[designmr]

thank you tbuelna, I appreciate the reply

 

[Tmoose]

I guess I would not consider PVC foam board too be fiberglass.

Am I missing something?

regards,

Dan T

 

[designmr]

Tmoose. Thank you for you reply. In some case our drawings do call out material as "2 PLY EPOXY/ 7781 FIBERGLASS W/ POLYMER FOAM CORE".

 

[berkshire]

Designmr,

"In some case our drawings do call out material as "2 PLY EPOXY/ 7781 FIBERGLASS W/ POLYMER FOAM CORE".
In the case you have just described you are dealing with a substrate of epoxy resin with two layers of fiberlass cloth over the PVC foam.
This is a typical spec for a light weight structure such as an aircraft part. The curing process for powder coating requires that the material be melted in an oven. The curing temps for the powder, which is most often a pigmented epoxy resin closely approach the forming temperatures of the PVC foam. you are likely to get distortion of the finished part.
Mil-PRF- 23377 is a spec for a two part epoxy primer that can be applied at room temperature, you will still need a top coat over the primer
MIL-PRF-85285, available in FED-STD-595 Colors is such a spec. It should be noted that there are different Mil Specs for the final use of the product such as ; aircraft , ground equipment , seaborne use/ Vessels.
B.E.

You are judged not by what you know, but by what you can do.

 

[designmr]

Well B.E. ALL one of our drawings calls out is:

PAINT PER MIL-PRF-24712A TYPE III, CLASS 2A FED STD 595B #17925 (INSIGNIA WHITE).

Seems we are missing a bit on this one...

Thank you for your reply

 

[berkshire]

designmr,
The spec you just mentioned definitely is a powder coating spec. It would appear that is in error.
The spec I mentioned is for a Poly urethane top coating suitable for use over the two part Epoxy primer you mentioned in your first post.
It would appear that you have some back tracking to do. The powder coating spec can only be used if the melt point of the powder is lower than the glass transition temperature of the Epoxy resin used in the layup of the glass fiber, which I think is unlikely.

You are judged not by what you know, but by what you can do.

 

[designmr]

Berkshire, hence our problem. Thank you all for the replies. BACK tracking indeed...

 

[tbuelna]

designmr,

Make sure you read the MIL-PRF-23377 spec carefully, especially sec. 3.11(f) dealing with surface prep of FRP surfaces:

"3.11 f. Apply over pretreated metal. On fiberglass-reinforced plastic, a prior coating of wash primer in accordance with MIL-C-8514 will facilitate stripping without damage to the fiberglass."

 

[designmr]

Thank you tbuelna...

 

[berkshire]

designmr,
Be careful to use a wash primer exactly as recommended by the maker, If the proportions of the catalyst are not exact, free Phosphoric acid can be left on the surface of the part, causing trouble with the epoxy primer.
B.E.


You are judged not by what you know, but by what you can do.