Surface Finishing Alternative

Owned by Maciek Pajak (Deactivated)
Last updated: Feb 02, 2021
5 min read

 

Adhesive Teflon

 

I am not entirely sure about the name of this product but, in this little article, the author of explore composites outlines the various positives and negatives of this handy little material. What it is, is pretty much a sticker, you just stick it onto the material you’d like to use and call it a day.

 

Options

There are several parameters to take into account when choosing a product like this:

  • Thickness

  • Adhesive

  • Scrim

  • Porosity

  • Stretch

 

Thickness:

The thickness will play a part in the surface quality and conformability when sticking the film to a curved surface.

0.003”/0.1mm:

  • Rally thin

  • Easy to tear

  • doesn’t do much to pad out imperfections

  • Adding 0.0025” of adhesive will give it a total thickness of 0.0055”

The author notes that his favourite is 0.005” film with 0.0025” adhesive, he says that it is still cheap enough while it provides a smoother and easy-to-release surface.

 

*Thicker film will be more expensive”

 

Adhesive:

The two main adhesive types are Acrylic and Silicone.

 

Acrylic:

  • Much, much cheaper

  • it is a one-use product, no way you’ll be able to reuse it

Silicone

  • Obviously, more expensive

  • Is said to be a much nicer option

  • Has the benefit of being able to handle a lot of rough treatment as cooking or vacuum bagging.

 

Scrim

There are two options with this…you either have a fiber scrim reinforcement or not.

 

Having a fiber scrim reinforcement will:

  • Strengthen the film

  • Great for relatively “flat” areas

  • Limits the contour-ability on curved surfaces

 

The author mentions that he advises going to the reinforced king because it is much easier to put down flat without stretching/warping and also if you need to remove it, it is said to come off easily.

 

Porosity

I am not entirely sure what his explanation means but I’ll give it a go

 

You can either get air-tight films or ones that will allow air/moisture to pass through them

 

He says that there are times that porosity is helpful, there are no bubbles when you stick it down which is nice.

He does say that he generally prefers going for the low-porosity film for cheap/quick and dirty molds (I do not know what this means, maybe you can interpret it).

he says “MDF is enough trouble without it pushing moisture into your parts”

Finally, he indicates that if we are only surfacing composite molds that are already air-tight, the porosity will not be an issue.

 

Stretch

The author indicates that the thicker, reinforced surfacing films will not stretch.

 

To deal with contours, you will have to cut little darts and laps which he indicates sucks.

 

He says that thinner Teflon films and those without scrim are sorta stretchy so gentle curves are ok but, we will have to do a lot of what are called “wallpaper cuts”(I will explain this later).

 

The author points out that “high-elongation fluoropolymer film like the Toolwright 3 (350% elongation)” will stretch a lot but it also has its limits, the following is an example:

How to actually use it

This film is forgiving for what he calls “crappy surfaces” compared to other release options.

 

The following steps should be followed to ensure the best results:

  • Make sure your surface is free of dust/contaminants, it will keep the adhesive backer from sticking

  • To combat the above issue, if you get contaminants stuck under the film, you must either make small slices and pick them out or leave them and you will have little indentations in your final part

  • You can then use a squeegee to put it down without wrinkles/bubbles

  • This may need some interpretation:

    • “For large surfaces, that are fair and well sanded, it may make sense to bring the finish to a higher finish level than seems needed to ensure better adhesion of the film”

      • I’m not entirely sure what this means but it seems important

  • He outlines how he met people who would sand it to 320 grit and then go over it with a buffing compound quickly.

  • Doing the above step could also help to make it easier to “patch” the film if it gets damaged after demolding many times.

  • The following is the “key detail” to getting neat results with the film”

    • The wallpaper cut also called the “double-cut”

      • This method is how to get seems that butt up and don’t overlap.

      • You start by overlapping the layers at the edges by around 1/2” (12mm) and then cut neatly through both layers somewhere in the middle of the lap.

      • You then want to leave enough of an “off-cut” on the bottom layer that you can peel back the top and pull out the strip you cut off without breaking it.

      • This takes some practice, so it is advised to do a bit before doing it on the actual mold.

      • The video below will show exactly what the wallpaper cut looks like at around the 1:40 timestamp

 

https://www.youtube.com/watch?v=QVXBojPldyY&feature=emb_title

According to the video, these are the main reasons to use adhesive film as a mold-release system:

  • It releases parts very well

  • No potential release transfer

  • Fast to apply

  • Works with rougher surfaces

  • Saves priming and sanding which are both very, very time consuming

  • Great for flat and flat-ish surfaces (which should be most of our panels…no?)

The following are also some reasons not to use this method:

  • It is much more expensive than what we do right now

  • The part surface will need primer and paint

  • Any cut in the film will end up printing into the part

  • Can get scratched and torn easily, must be careful!!

  • Can be very frustrating to apply to curved surfaces, in the video, it took him 30 minutes to apply it to a half-circle the size of a plate

 

The following are some of his conclusions:

  • If you don’t mind lines on your finished part and want high-quality composite parts ASAP, this must be for you!

  • It is quite expensive, but it can be a huge benefit for prototyping or custom builds

  • He says that this is good for prepregs as it gives you the best parts from inexpensive tooling

 

My conclusions:

  • It is quite expensive as one type of roll, around 16m long and around 1m wide costs $940.70 (I believe USD since the company is based in California)

  • It can save us a lot of time as we don’t need to apply our surface finishes that take a long time to apply and cure, from what it seems we will be able to do this process relatively easily since a lot of our parts are not that curved (I think).

  • It seems like it fits our needs perfectly as it is very useful for prepreg

  • We could use it in the future if it is useful