Handling Tacky Pre-preg. 1

[jaiman79]

I would greatly appreciate if anyone can help me with the following problem we are having with regards to pre-preg handling and lay-up.

We at present place the pre-preg in the freezer for a few minutes just before to be able to remove the backing of the pre-preg otherwise under ambient temperature we are struggling like crazy and distorting the pre-preg material when trying to remove the backing on either side of the pre-preg.

Not only that but when it comes to laying up the pre-preg we are finding it extremely difficulty moulding it around the mould tools as it is so tacky (even though we are doing it in a temperature controlled clean room). Also to mould the pre-preg around the mould tools keeping the one layer of backing on stops the material from moulding into the small grooves in the tool. We are tempted to resort to using barrier cream just so it makes the job easier but I understand that as introducing contaminents into the pre-preg which could alter the properties of the material.

If any one knows of any ways we can overcome the above problems I would greatly appreciate it. Any suggestions and ideas welcome. Thank you

 

[SWComposites]

Ask the supplier for less tacky material?

Buy material from a different supplier?

 

[Compositepro]

My guess is you are working with a room temperature curing prepreg. This requires the resin to flow at room temp. which results in high tack. About all you can do is use cooling to lower tack. Make the room colder and wear a jacket. There are spot coolers that run on compressed air (Vortec, Exair). There are also freeze sprays. These are liquids than are under pressure in the can but boil at less than 32F at ambient pressure. These boil-off leaving no residue. You could even used dry ice.

Or use a more standard prepreg with the desired tack, but which requires heat to cure.

 

[jaiman79]

Thank you SWComposites & Composites for your advice.

I have taken your suggestions on board and looking into the ideas suggested.

Thanks again.

 

[Compositepro]

One other technique that is commonly used in the rubber industry is to dust the surface with talc or some other inert filler.

 

[allcomposites]

I assume you are using out-of-autoclave prepregs. You have to cool-down the mold to properly use them. You can use a copper pipe molded at the shape of the composite mold and circulate cold water or use a closed circuit if available. Once the prepreg touches the surface of the mold it will easily hold on it.

If you cool-down the room, be careful with the humidity level.