Polyester resin: life & thinning with styrene

Discussion in 'Fiberglass and Composite Boat Building' started by burke, Jan 7, 2017.

  1. endarve
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    endarve Junior Member

    Personal attacks and I just got here? I've been lurking a while and previously read your misinformation and kept quiet. You obviously lack hands on shop time. By the way, saturated cloth does not draw resin out of wood or foam. That is, except when the individual doesn't know how to wet out the cloth properly in the first place. And a styrene wipe gives superior bonding compared to using acetone. Anyone can do empirical testing to prove fact from fiction.

    E
     
  2. ondarvr
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    ondarvr Senior Member

    There was no personal attack on you, it was the information you supplied that was suspect.

    Interesting thought, but my "hands on experience" started in the 60's, and continues to this day. Started young and worked up through the industry from sweeping floors and grinding to plant manager, then general contractor, and now in tech service teaching people how to use the products.

    Bond testing on wood was something I was very involved in for a long time. One example is a customer I had a that used about 3 tankwagons of resin per month and we did a great deal of testing, every panel they made had cutouts that went through destructive QC testing. (Panels were 40' X 10')

    They started by sanding every sheet, then built a machine to punch small holes, over several years of testing they stayed with sanding because there was a benefit on most sheets, but stopped punching holes because it didn't help at all.

    The best results were achieved by pre coating the wood with infusion resin and letting it cure, then laminating on it, most of these panels were bagged.

    Allowing the pre coat to cure was too slow for production, so they used extra resin, and the bagging helped. The exact makeup of the skins (veneers) on each sheet had a big effect on how it failed.

    This was only a small part of my bond testing experience.

    I asked what the styrene wipe did, and to be specific, you didn't supply any info to explain why it helps, only that you believe it does.
     
  3. ondarvr
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    ondarvr Senior Member

    We can move on to using 3 year old resin if you wish.
     
  4. endarve
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    endarve Junior Member

    Looks like I'm getting more flak here...since a 3 yr shelf life is "not accurate", what exactly are you basing that on? What is the shelf life of the chemicals, not the mfgs spec which is typically cut short only to CYA.

    I'm not exactly an advocate for others to use "old" poly resin but 3 yrs is not a deal stopper to me and is worth a risk if someone is on a tight budget, etc. Fact: I used 2005 epoxy resin (because I discovered 7.5 gals out of sight and out of mind) on a pt ply boat floor with only surfacing mat 4 yrs ago and it's still going strong. Is it compromised? Probably, but evidently not beyond its required performance duty. It's painted with Brightside. The boat hangs in my boat lift, is on saltwater, exposed to harsh tropical weather and gets used every week. No problems and I consider it just another resin experiment.

    Concerning resin life, I've kept samples to test (gallons of each) of both polyester laminating and finishing resin, and epoxy resins for many years to see what happens. Poly was usable for the better part of 5 years and completely gelled at 7-8. Hard as a rock with dim ambient shop light (was in poly jug) to kick it. Epoxy (1:1 & 5:1) stayed the same viscosity for 10 yrs in a clear 5 gal jug. I pulled samples every couple of years and all kicked same as when new. I didn't do destructive testing to tell how the hardness was compromised. I have not called DuPont Labs to see what the official shelf life is but based on other chemicals I've called about it's a lot longer than the mfgs say.

    Another bit of testing I have done is make epoxy cubes of different brands and put a hammer to them to compare hardness. There is a huge difference between brands. System Three T-88 (structural epoxy glue) blew away WEST and other glues for hardness.

    About pine sucking resin and highly variable. Not where I come from. I've done pine, fir, spruce, oak, mahogany, teak, etc. I've cross cut a lot of wood boat pieces, stringers, transoms to see how deep the resin penetrates and it is microscopic. Epoxy and poly saturation to more than 1/16" depth is rare (balsa end grain) and mostly a myth. Basically I believe it when I see it.

    E
     
  5. endarve
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    endarve Junior Member


    That's out of context with this simple stuff and just chest thumping to impress. Whoopie and big deal, I have degrees, was a plant mgr for 4500 people and worked frp since the 60s...BFD. But you never tested gluing frp parts with and without wiping with styrene? Why don't you try it and post the results. You don't believe me and I have done the testing. Get 4 small frp laminate parts, sand joining sides completely flat, wipe 1 set with styrene, the other set with acetone. Use nothing but poly resin to glue each set together. Let cure a day or two, do destructive testing. End result is the styrene parts stay stuck together way longer than the other parts.

    I'm not interested in discussing resin shelf life with you because you have no experience using old resin or testing old resin.
     
  6. ondarvr
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    ondarvr Senior Member

    I never said I haven't tested styrene aided bonding, I asked you why you think it helps.

    Acetone is an inhibitor, so any left in the wood can compromise the cure, which can result in a poor bond, styrene will react with the resin, so seeing a difference in the bond is logical.
     
  7. ondarvr
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    ondarvr Senior Member

    Epoxy ages differently and much better than polyester, but I don't know enough about epoxy to say anything, so I'll leave that to others.

    The reason there's a 3 month shelf life on most polyester is because it's formulated to a specific set of specifications, viscosity, gel time, peak exotherm, etc. Polyesters tend to drift over time, so for three months the gel time and other aspects of the resin will still be in the correct range for production. For an unknown period of time after that the resin may or may not be exactly in spec, but could still cure correctly, but over time the physical properties of the cured product are affected, the degree of degradation wouldn't be known without lab testing. Eventually the cure will be so poor that it will fail in some way in the field, and that's if it will get hard enough to even make a part.

    Luckily most of the things made with polyester are over built, so a certain amount of reduction in the physical properties may not be noticed.

    You mentioned testing different epoxies, the problem is there are thousands of different formulas, so doing the same type of test with each one should logically lead to different results. If you want to test how well a cube holds up to a hammer blow, then test the resin spec'd for that type of stress, not random samples designed for other purposes. The suppliers can give you that info.

    Just because a Honda Civic can't pull a 35' travel trailer as well as a 1 ton diesel dually doesn't make it a bad car.
     
  8. endarve
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    endarve Junior Member

    Well, when you actually do an empirical bonding test with styrene it will turn "logic" into experience. Acetone is a distant 2nd place when compared as previously noted.

    Many people preach to use acetone to thin resin. I've seen posts that even say styrene isn't the correct thinner for poly. Bogus info and not the best practice but it works. Only a few know what the signs are with acetone thinned gelcoat. Do you know specifically what the signs are and when do they show up? Regardless, why are you asking me about styrene? Its the results that matter, not what I think or imagine in lala land. Chemical linking is basic stuff.
     
  9. endarve
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    endarve Junior Member


    There isn't a problem with my testing because it's casual and specifically for me and the products I personally use. I've played with resin enough to know how to push the envelope when needed and have no liability to others. It is in no way related to factory production, which has totally different QC specs.
     
  10. ondarvr
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    ondarvr Senior Member

    I did tech service on gel coat for 20 years, so if you wish to discuss it in detail we can. This was for the largest suppliers of it, I worked with the testing lab and chemists on a daily basis. My job was to take that info into the field so users of the products could get the best possible results on a consistant bases.

    I do enjoy these discussions, but it's getting late, so I'm out for now.
     
  11. endarve
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    endarve Junior Member

    With kindest regards the answer is an easy two short sentences and posting work history took longer than a proper answer. This should have been a fast no brainer reply. Same deal as the styrene bonding.
     
  12. ondarvr
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    ondarvr Senior Member

    Answers like that are never that short, there are many possibe negative results from using acetone or styrene to thin resin and gel coat.

    The short answer is that almost every cosmetic and physical property of both products is compromised, the more you add the worse it gets.

    At first I thought you meant you were a plant manager in the composites industry, but the plant manager part appears to be unrelated to this subject. With that in mind I understand why you think it's a quick two sentence answer.
     
  13. ondarvr
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    ondarvr Senior Member

    This conversation seems very familiar, did we have a very similar discussion in the past, possibly on another forum?
     
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  14. kilocharlie2
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    kilocharlie2 Junior Member

    Endarve, good buddy, I do not intend to give you flak, just that my observations have been different.

    I've typed a full response 4 times and the computer keeps making it disappear, so for now, just an apology.

    ********************

    OK, so that went up, and first 2 tries at editing this did not.

    I agree that epoxy usually has a longer shelf life than polyester resin, especially if the epoxy resin cannot smell the hardener. I keep part A and part B in different metal cabinets. Anal retentive? Maybe, but it works pretty good for me :)

    My opinion on "old" polyester resin is based on personal experience. We may be using different brands with different shelf lives or in different conditions or both...its the part about it appearing to have thicker than original viscosity that alarms me, that's why I'd just buy some fresh stuff if I was going to make a big project.

    My opinion regarding the variability of pine absorbing resin probably comes from having been in shops that used everything from old kiln dried wood to fresh green lumber, all sizes and cuts of grains, perhaps every kind of pine, from various brands of resin, from thinned resin to resins thickened by micro balloons, cotton flok, saw dust, chopped glass, and a host of other fillers, and idiots trying to bond wood to wood with it (wood glue seems to do a much better job of bonding wood to wood!).

    My best results bonding polyester resin and fiberglass to wood seemed to come from first painting the bare wood with thinned polyester resin, then a second coat of thickened poly when the first coat was greenstage, then the wetted out composite layup, then the vac bag. If you have a better routine, by all means use it.
     
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  15. SamSam
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    SamSam Senior Member

    Were these used on semi trailers? Can you give a short description of the process? I'm wondering how did they make a flat surface that big and the type resin used and did they scarf the plywood pieces or just butt them together?
     
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