resin infusion process using high-temperature curing epoxy resin

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 Posted 19/01/2012 17:18:45
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Dear all

1. I am thinking of using a high-temperature curing epoxy resin system to perform vacuum assisted resin infusion process. The curing temperature of my resin can be as high as 180 degree celsius. I am wondering if any of your products could be suitable for this requirement? I realize that the vacuum bag gum tape (high temp) that you have is suitable for use at temperature up to 160 degree celsius...

2. another small question is that the infusion mesh which helps the resin to flow through the mould, will the finished product(composite)'s surface finish  has the same texture as the that of infusion mesh as I need my composite to have as good surface finish as possible. 

Sorry that I am just the beginner thinking of using resin infusion process and was impressed by the video that you uploaded onto the Youtube Smile

Many thanks in advance! Any suggestions would be greatly appreciated!

Chris
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 Posted 20/01/2012 08:46:58
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Hi Chris,

You're welcome to ask questions, that's what the support forum is here for Smile

Question 1.

When you say you're thinking of using a 'high temperature curing epoxy' do you actually mean an epoxy that will only cure at high temperature or do you mean an epoxy that can take a high temperature once it's been cured/post cured?

There really arn't many products out that that sufficiently low viscosity (runny) at room temperature to be able to infuse with them that then won't cure until they reach a high temperature (like 180C). The high temperature curing epoxies that you're most likely to encounter would be the types used in pre-pregs but they're thick and tacky at room temperature, getting much low in viscosity as the temperature increases (as they cure in an oven/autoclave). They certainly wouldn't be suitable for infusion.

If you're referring to a an epoxy that can take a high temperature (like our Extra High Temp epoxy) then you might well be able to use this for infusion; it's not ideal because it's a higher viscosity than you would want for an infusion, but given the right flow media, laminate and set-up it should be possible to infuse with it.

With the high temp epoxies they tend to cure at room temperature and then require a post-cure at elevated temperature in order to realise their full HDT (Heat Distortion Temperature). The first part of the 'post cure' should be done in the mould to avoid distortion, ideally still under a sealed bag (if the part has been infused or vac bagged) up to at least 80C for  afew hours. If your entire set-up (the mould, the tape, the film etc.) could take it then you could continue the post cure in-mould up to 180C (the max post-cure temp for our Extra High Temp Resin) but if you mould/tape/film can't take any more temp (it's quite likely that your mould won't for example) then you'd be fine to de-mould and continue the post cure on a steady temperature ramp up to 180C without any real risk of distortion.

Question 2.

The infusion mesh certainly shouldn't leave any 'print through' or texture on the A side (the outside/good side) of your part. The peel-ply seperates the part from the infusion mesh on the the inside (the B side)  and so any texture from the mesh even on the inside is kept to a minimum but you will likely see a faint texture of the mesh on the inside of your laminate (although the obvious texture will be that of the impression of the peel ply).

I hope this helps, Matt


Matt Statham
Easy Composites / Carbon Mods - Technical Sales


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 Posted 24/01/2012 16:06:03
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Many thanks!

The epoxy resin I have is a two-component (resin/hardener) epoxy resin system, therefore its recommended curing procedure starts from 100c up to 180c. The initial mix viscosity at room temperature is around 5000 cps and much lower at elevated temperature (~700 cps at 40c). I am thinking of a proper and effective way to make a composite laminate (e.g., carbon fibre lamination) using this type of epoxy resin. Instead of resin infusion, I realize that vacuum bagging along with wet lay-up process could be a good way to make it. For example, I could place the material and poured with epoxy resin, and covered with release film (maybe perforated to let excessive resin squeezed out) and breather cloth, and finally bag it using sealant tape. After bagging, I may apply the vacuum and starting the curing procedure from RT up to 180c. 

Do you think this method that I came out is suitable in the case of this type of resin system? Or could you suggest a better way? Another problem is that the sealant tape, vacuum bag, vacuum connector etc. have to withstand the temperature up to 180c. I realize that your company has a range of products for vacuum bag consumables except for the sealant tape which you said can only work for 160c.

I would really appreciate your suggestions or advice.

Chris
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 Posted 24/01/2012 17:04:10
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Hi Chris,

The epoxy resin I have is a two-component (resin/hardener) epoxy resin system, therefore its recommended curing procedure starts from 100c up to 180c.


To be clear, being a 'two-component epoxy resin system' doesn't give any indication that such a resin system would have a cure temperature of 100-180C. The system you're using might have that cure requirement (very unusual for a laminating resin) but I just want to point out for the benefit of others that a two component epoxy resin system is far more likely to be designed at ambient than at 100C+. Out of interest, what resin system is this that you're talking about?

From what you're saying, if this resin has a very high viscosity at room temperature then it might not wet out your reinforcement at room temperature properly, if you then put a perforated release film and breather on top of it and then vacuum bag it before cranking the temperature up it strikes me that there's a very good chance that when the viscosity drops the resin will flow very easily through a P3 perforated film and into your breather cloth, just as easily as it will wet out the laminate properly. If this happens you'll have a very dry laminate (not what you want).

Vacuum bagging is notoriously tricky to get right when it comes to the amount of bleed-off of the resin. You will need to control the vacuum pressure, the amount of perforation and how much breather you use.

What are your reasons for using your unusual choice of resin? - If I understand why you need to use such a resin system, maybe I'll be able to suggest how you can use it.

--Matt


Matt Statham
Easy Composites / Carbon Mods - Technical Sales


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