Epoxy or Polyester???
06-15-2007, 02:23 PM
#4
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RE: Epoxy or Polyester???
Chuckc, , ,
They are both basically variations of polymers. One uses an epoxy catalyst while the other uses MEK mixed in at about 2% per volume.
The polyester variety is most common in boat manufacture, and other high production applications because of it's easy use with spray equipment, and the ability to control it's final hardness. Yes, technically you can spray epoxy, but you also run a serious risk of hardening up the spray gun! In the case of polyester however, the MEK is either injected or atomized with the resin outside of the gun. Or the lower budget version of counting out drops of MEK.
As a hardness comparison, I would say that the epoxy would be somewhat harder. If applied too thick, it would fall into a rehlm of being brittle.
Note the spray gun that I'm using in the picture. The plane is the XP-67 Moonbat. The whole thing is done in about 10 minutes using about 2 ounces of resin!
The spray gun is unlike anything thats used in the auto industry.
Spraying polyester requires very special equipment that will set you back about $1,300 to get set up (providing that you already have a suitable compressor).
Cost is probably the predominant reason that most modellers just use epoxy.
In-so-far-as modelling goes, I like using polyester. I can spray a very thin, dusting coat on the fiberglass cloth that requires minimal scraping at all. Most of the time, I never need to scrap it out anyways! Go for lunch, come back and pick up the gun and start spraying again! Clean-up is very easy using Gunwash. You can control the hardness of polyester by using an additive.
If your going to consider polyester, and you have the funds, counting 4-5-6-7 drops of MEK is not the way to go. I've been set up for spraying for along time and would find it hard to look back.
They are both basically variations of polymers. One uses an epoxy catalyst while the other uses MEK mixed in at about 2% per volume.
The polyester variety is most common in boat manufacture, and other high production applications because of it's easy use with spray equipment, and the ability to control it's final hardness. Yes, technically you can spray epoxy, but you also run a serious risk of hardening up the spray gun! In the case of polyester however, the MEK is either injected or atomized with the resin outside of the gun. Or the lower budget version of counting out drops of MEK.
As a hardness comparison, I would say that the epoxy would be somewhat harder. If applied too thick, it would fall into a rehlm of being brittle.
Note the spray gun that I'm using in the picture. The plane is the XP-67 Moonbat. The whole thing is done in about 10 minutes using about 2 ounces of resin!
The spray gun is unlike anything thats used in the auto industry.
Spraying polyester requires very special equipment that will set you back about $1,300 to get set up (providing that you already have a suitable compressor).
Cost is probably the predominant reason that most modellers just use epoxy.
In-so-far-as modelling goes, I like using polyester. I can spray a very thin, dusting coat on the fiberglass cloth that requires minimal scraping at all. Most of the time, I never need to scrap it out anyways! Go for lunch, come back and pick up the gun and start spraying again! Clean-up is very easy using Gunwash. You can control the hardness of polyester by using an additive.
If your going to consider polyester, and you have the funds, counting 4-5-6-7 drops of MEK is not the way to go. I've been set up for spraying for along time and would find it hard to look back.
06-15-2007, 03:19 PM
#5
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RE: Epoxy or Polyester???
Iv'e used K&B Polyester for 35 years, and I for reasons you Mention, it is great for surfacing. and I have sprayed
it with a $13.00 buffalo touch up gun with Great success. It is fast and can be flawless. But as far as layup's go
I like Epoxy glass fuses. It bonds to better during construction. It is amazing just how much they are alike, after they completely cure.
What are you guys using to install formers in your jets? From what I can tell, Hysol is the product of choice.
it with a $13.00 buffalo touch up gun with Great success. It is fast and can be flawless. But as far as layup's go
I like Epoxy glass fuses. It bonds to better during construction. It is amazing just how much they are alike, after they completely cure.
What are you guys using to install formers in your jets? From what I can tell, Hysol is the product of choice.
06-15-2007, 03:30 PM
#6
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RE: Epoxy or Polyester???
Hysol - yes, works very well, very convenient and very neat.
Reason I asked about testing is that I have worked with polyester and epoxy a bunch, but not vinyl ester. Some of these planes coming over have a smell that I would associate with polyester (maybe vinyl ester to?) and not epoxy. Smell's not too accurate though; would be better to have a chemical test or something to be able to be "objective".
I think Ronnie was right, but I'm not certain ALL Feiba (sp?) jets are polyester, though I highly suspect a few are that I've seen.
Has the quality of polyester resins improved? I know the vinyl ester resins are supposed to be much better.
Reason I asked about testing is that I have worked with polyester and epoxy a bunch, but not vinyl ester. Some of these planes coming over have a smell that I would associate with polyester (maybe vinyl ester to?) and not epoxy. Smell's not too accurate though; would be better to have a chemical test or something to be able to be "objective".
I think Ronnie was right, but I'm not certain ALL Feiba (sp?) jets are polyester, though I highly suspect a few are that I've seen.
Has the quality of polyester resins improved? I know the vinyl ester resins are supposed to be much better.
06-15-2007, 03:47 PM
#7
Senior Member
RE: Epoxy or Polyester???
drdoom, , ,
There are different types of polyester. Try the layup resin. It's specifically designed for multiple applications, and a fraction of the cost of epoxy.
Chuckc, , ,
Polyester's key ingredient is Styrene. The smell of styrene is unmistakable and fills the whole workshop..
Hysol definetly gets two thumbs ups. [sm=thumbup.gif]
There are different types of polyester. Try the layup resin. It's specifically designed for multiple applications, and a fraction of the cost of epoxy.
Chuckc, , ,
Polyester's key ingredient is Styrene. The smell of styrene is unmistakable and fills the whole workshop..
Hysol definetly gets two thumbs ups. [sm=thumbup.gif]
06-15-2007, 06:16 PM
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RE: Epoxy or Polyester???
Vinyl Ester is chemically a lot closer in the Linking and structure of the polymer chains to Epoxy than straight Polyester. This is why it is more tolerant to many chemicals.
Vinyl Esters, Generally have a lower shrinkage rate and therefore less internal stress within the laminate. Because of this, the laminates are similarly strong to Epoxy laminates. Working with Vinyl Esters is very similar to working with Polyesters. The catalysts are mildly different but the cross linking and curing process is similar.
There's 2 ways to test whether you have Epoxy or Polyester. either way you need a small piece of the laminate that you are prepared to destroy.
1 - Get a solvent (MEK - Methyl Ethyl Ketone works well but Acetone will also work - it just takes longer). Apply it to the laminate and see what happens. If it is polyester, the surface will become "Tacky" fairly quickly, If it's Epoxy, it wont (at least not for a long time).
2 - Burn a piece of the laminate - the smell will give it away.
Vinyl Esters, Generally have a lower shrinkage rate and therefore less internal stress within the laminate. Because of this, the laminates are similarly strong to Epoxy laminates. Working with Vinyl Esters is very similar to working with Polyesters. The catalysts are mildly different but the cross linking and curing process is similar.
There's 2 ways to test whether you have Epoxy or Polyester. either way you need a small piece of the laminate that you are prepared to destroy.
1 - Get a solvent (MEK - Methyl Ethyl Ketone works well but Acetone will also work - it just takes longer). Apply it to the laminate and see what happens. If it is polyester, the surface will become "Tacky" fairly quickly, If it's Epoxy, it wont (at least not for a long time).
2 - Burn a piece of the laminate - the smell will give it away.
06-15-2007, 10:54 PM
#10
RE: Epoxy or Polyester???
Has anyone read the warning label on MEK, scare the heck out of you. I worked oilfield as a young man and got bathed in MEK once when a drum got dumped on me, burned like heck. Glad I didn't know how dangerous that stuff was when it happened, I might have freaked. Maybe that's the reason I got cancer years later, hmmmm.
Sorry if this statement was a bit off topic.
Sorry if this statement was a bit off topic.
06-16-2007, 08:40 PM
#12
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RE: Epoxy or Polyester???
MEK - yes; know about the health risks - I'm an Industrial Hygienist (by degree, etc.) and have worked in the chemical/refinery business for a few years. Saw some scarry stuff - guys washing their tools with straight, hot benzene, MEK etc. I can't tell you the number of times I've had guys break open a line wrong and get absolutely drenched with benzene/toluene/xylene. The grossest is a coker unti - the finished product is like coal and was a very fine dust. The whole place was just permeated with this black filth. We even had special showers for the guys to wash off in before they left, but would still sweat out the coke after work when they exercised.
To bring it back on-topic; there are quite a few nasty exposures in this hobby, but not as heavy or long a duration.
I think I've got some testing to do...will let you know.
To bring it back on-topic; there are quite a few nasty exposures in this hobby, but not as heavy or long a duration.
I think I've got some testing to do...will let you know.
06-17-2007, 10:44 AM
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RE: Epoxy or Polyester???
ORIGINAL: SECRET AGENT
Hey Swat Team,
Yeah, I can be seen a mile away by a night vis.!! I don't even need a streamlight when doing raids. My willy looks like a chem light, HAA
.
Hey Swat Team,
Yeah, I can be seen a mile away by a night vis.!! I don't even need a streamlight when doing raids. My willy looks like a chem light, HAA
.
I think that last is more info than we really need!!!!!!!!!!!!!!!!! LOL
