Polyester or Epoxy resin?
03-09-2019, 07:58 AM
#1
Polyester or Epoxy resin?
Just wondering what you guys prefer.
I exclusively use West Systems Epoxy opposed to polyester resin when I do any fiberglass repair.
I am in no way related to West Systems, I just believe it to be a superior product over the standard polyester resins available.
I exclusively use West Systems Epoxy opposed to polyester resin when I do any fiberglass repair.
I am in no way related to West Systems, I just believe it to be a superior product over the standard polyester resins available.
Last edited by 71warbonnetyello; 03-10-2019 at 11:32 AM. Reason: too much infromation and zero interest in post
03-10-2019, 11:47 PM
#3
Le Mans Master
Member Since: Dec 2009
Location: Saskatoon Saskatchewan
Posts: 6,397
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I use polyester unless I'm working on SMC. I can't get epoxy resin locally, I have to have it shipped from 1600 miles away and it gets pretty pricey.
Last edited by Priya; 03-10-2019 at 11:48 PM.
03-11-2019, 12:56 PM
#4
Melting Slicks
I've gotten so many different opinions from body guys on this. One guy I know who worked in a shop that did primarily Corvettes who said they always used polyester on everything including SMC for many years without any issues. Other guys I've talked to say you can't use polyester on SMC. Who;s correct, I don't know.
Mike
Mike
03-13-2019, 04:09 PM
#5
Melting Slicks
On my 71 I started using polyester on the front end panels then shifted to epoxy for the doors back after reading about the different materials used.
In fact I ground out some polyester repairs on panels to re do in epoxy and they were in no way going to come off.
The `71 had a mixture of panels ranging from the old polyester to Gennite and the first SMC panel which was first used on the rear fenders sometime during the year.
Here is is some of the info I found when I was looking.....
68- All Polyester resin fiberglass, generally darker gray, black.
69- All polyester early with various shades of gray, black. Later 69 some doors made of a product of General Tire called Gennite. This product was similar to SMC and was a light gray.
70 - More Gennite panels used in different locations, more light gray panels used.
71 - A continuation of the trend to Gennite. The first SMC panels used, on late rear quarters. SMC panels had a marble effect and a light gray color.
72- More use of SMC for other panels, still a mixture of polyester, gennite, and SMC.
73- The trend to mostly SMC continues. The rear deck was the last polyester panel still to survive.
74 - With the change to the rubber rear bumper, the rear deck was redesigned, and the last vestige of polyester was gone. Even with all SMC there was varying shades of gray.
75- 82 All panels were the marble gray SMC. Still with varying shades of gray.
" In 1968 the Chemical / Plastics Division of the General Tire and Rubber Company introduced a low shrink wet resin system , known as Genite"..... General Tire became a major suplier of Corvette body components to the St. Louis assembly plant." " During 1970, another improvement in fiberglass technology, called low-shrink Sheet Moulded Compound (SMC), was introduced ..... The rear quarter panels on the 1971 Corvette were the first parts manufactured using this system."
In fact I ground out some polyester repairs on panels to re do in epoxy and they were in no way going to come off.
The `71 had a mixture of panels ranging from the old polyester to Gennite and the first SMC panel which was first used on the rear fenders sometime during the year.
Here is is some of the info I found when I was looking.....
68- All Polyester resin fiberglass, generally darker gray, black.
69- All polyester early with various shades of gray, black. Later 69 some doors made of a product of General Tire called Gennite. This product was similar to SMC and was a light gray.
70 - More Gennite panels used in different locations, more light gray panels used.
71 - A continuation of the trend to Gennite. The first SMC panels used, on late rear quarters. SMC panels had a marble effect and a light gray color.
72- More use of SMC for other panels, still a mixture of polyester, gennite, and SMC.
73- The trend to mostly SMC continues. The rear deck was the last polyester panel still to survive.
74 - With the change to the rubber rear bumper, the rear deck was redesigned, and the last vestige of polyester was gone. Even with all SMC there was varying shades of gray.
75- 82 All panels were the marble gray SMC. Still with varying shades of gray.
" In 1968 the Chemical / Plastics Division of the General Tire and Rubber Company introduced a low shrink wet resin system , known as Genite"..... General Tire became a major suplier of Corvette body components to the St. Louis assembly plant." " During 1970, another improvement in fiberglass technology, called low-shrink Sheet Moulded Compound (SMC), was introduced ..... The rear quarter panels on the 1971 Corvette were the first parts manufactured using this system."
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20mercury (03-13-2019)
03-13-2019, 04:13 PM
#6
Le Mans Master
I used Poly-resin back in 2004-2006 when I molded and shaved the car. Everything has either swelled or popped so I plan on redoing everything next winter in the West Systems. I plan on driving the car this summer (been sitting for 10 years) before I redo it all again.
03-13-2019, 05:27 PM
#8
Burning Brakes
Using Epoxy is a better option I believe. It is a little harder to 'wet out' when laying up, but it is suitable, and superior in strength to that of general purpose polyester. Another big advantage of Epoxy is that it has zero shrinkage, unlike GP resin, which can shrink up to 5% in some applications.
You can use Epoxy on everything, but you shouldn't use GP resin on SMC panels. It is a well known fact that GP resin has not got good adhesion when applied in this situation. You might get away with it, but not good practice.
Good Luck👍
You can use Epoxy on everything, but you shouldn't use GP resin on SMC panels. It is a well known fact that GP resin has not got good adhesion when applied in this situation. You might get away with it, but not good practice.
Good Luck👍
03-13-2019, 06:43 PM
#9
Race Director
I use both types of resin and it depends on what I am repairing and I ALWAYS use my infrared heater and cure out the resin after it has gone through its initial cure.
It is odd that if a person laminates up mat and resin on a 60 F day....and then they do it a month or two later when it is 90 F. That certain dynamics are in play where possibly taking the repair a step further and make sure that the laminations are cured out very well. Resins are much like paint ...because to be honest...paints have resins in them. Not resin like we are talking about...but a resin nonetheless.. And IF a person does their body work and paints the car...and then leaves it in the garage over the winter thinking it is curing out in a cold garage...AND never force cured it....only to find out the first hot day of summer and they take the car out of the garage and body and paint problems happen. This is due to many factors and one of them can be they never got the body HOTTER than what the sun will make it. Now that is as about a logical as I can write it and doubtful anyone can dispute the fact of temperature having a important role. Unless you feel this is a bunch of hog wash...and then do it as you see fit.
30+ years of doing this stuff and hundreds of projects and no problems at all....other than trying out different resins in testing and seeing that they do not hold up.
I can say...and NOT saying that anyone reading this is the one I am talking about...because I am not...but I have seen enough poor attempts of someone who does not have a clue on how to correctly laminate up mat and resin.....or know that not ALL polyester resins are the same....or how to adjust 'things' and how much to apply in a laminating session. Clearly those people do not understand that the resin and mat work together and if the lamination is not done correctly...then....depending on where it is...it can fail. And I do not care on what type of resin is used.
YES...without a doubt.....WEST SYSTEMS epoxy resin is a better resin that polyester when a person begins to compare the properties of the resins. Now If I laminated up two parts...one in polyester and one in epoxy resin that if I were to test them by smashing them with a hammer...I guarantee you they they both would fail. Because it is obvious ...that polyester paneled Corvettes and those made with SMC both crack and fail.
DUB
It is odd that if a person laminates up mat and resin on a 60 F day....and then they do it a month or two later when it is 90 F. That certain dynamics are in play where possibly taking the repair a step further and make sure that the laminations are cured out very well. Resins are much like paint ...because to be honest...paints have resins in them. Not resin like we are talking about...but a resin nonetheless.. And IF a person does their body work and paints the car...and then leaves it in the garage over the winter thinking it is curing out in a cold garage...AND never force cured it....only to find out the first hot day of summer and they take the car out of the garage and body and paint problems happen. This is due to many factors and one of them can be they never got the body HOTTER than what the sun will make it. Now that is as about a logical as I can write it and doubtful anyone can dispute the fact of temperature having a important role. Unless you feel this is a bunch of hog wash...and then do it as you see fit.
30+ years of doing this stuff and hundreds of projects and no problems at all....other than trying out different resins in testing and seeing that they do not hold up.
I can say...and NOT saying that anyone reading this is the one I am talking about...because I am not...but I have seen enough poor attempts of someone who does not have a clue on how to correctly laminate up mat and resin.....or know that not ALL polyester resins are the same....or how to adjust 'things' and how much to apply in a laminating session. Clearly those people do not understand that the resin and mat work together and if the lamination is not done correctly...then....depending on where it is...it can fail. And I do not care on what type of resin is used.
YES...without a doubt.....WEST SYSTEMS epoxy resin is a better resin that polyester when a person begins to compare the properties of the resins. Now If I laminated up two parts...one in polyester and one in epoxy resin that if I were to test them by smashing them with a hammer...I guarantee you they they both would fail. Because it is obvious ...that polyester paneled Corvettes and those made with SMC both crack and fail.
DUB
03-14-2019, 05:49 AM
#11
Burning Brakes
I live in S.W. Florida and, because of all the marine activity, there is a great deal of experience with West Systems. It is what I used exclusively. What's nice is that you can use it not only for laminating but, with West Systems additives, as a filler. I believe that there is a benefit to not mixing types of products when doing bodywork.
03-14-2019, 11:40 AM
#12
Le Mans Master
Member Since: Dec 2009
Location: Saskatoon Saskatchewan
Posts: 6,397
Received 640 Likes
on
463 Posts
I live in S.W. Florida and, because of all the marine activity, there is a great deal of experience with West Systems. It is what I used exclusively. What's nice is that you can use it not only for laminating but, with West Systems additives, as a filler. I believe that there is a benefit to not mixing types of products when doing bodywork.
03-14-2019, 03:42 PM
#13
Race Director
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Priya (03-14-2019)