Problem: pull-out test brush is OK, but spraying film failed, only 3-4Mpa, polyaspartic topcoat film delaminate level by level when doing pull-out test. Request Date: Pull-out Testing above 7.5Mpa.
Background:
1. metal substrate
2. Polyaspartc topcoat on polyurethane
3. Machine spraying.
Problem: pull-out test brush is OK, but spraying film failed, only 3-4Mpa, polyaspartic topcoat film delaminate level by level when doing pull-out test.
1. Spraying test: Spraying by Graco equipment, thickness 200Micro, 2days later doing Pull-out Testing, Rubber adhesive is double compenont epoxy glue, result: 3Mpa. Topcoat film breack from top, remain thickness on spindle is about 20Micro, rest 180Micro stay on sample. Polish and repeat this testing, result is same, remain thickness on spindle is about 20Micro, rest 160Micro stay on sample.
2. Brush test: Same formulation , mix with same ratio, brush on sand-blast Fe sample, 2days after doing Pull-out Testing, same rubber adhesive, sample testing method, result is 10Mpa, all film glue to spindle, no remain on sample.
Annie, did you give the polyaspartic enough cure time before the pull tests? Also how did you prepare the polyurethane surface before you applied the polyaspartic?
Polyaspartic Polyurea Resin/Hardener Manufacturer Overseas Biz Manager at Feiyang Novel Materials export@feiyang.com.cn
@Malcolm, no special preparation on polyurethane. Problem is not adhesion of topcoat to primer, problem is polyaspartic topcoat cohesion is bad by spraying.
Annie, I would like to help you determine why this cohesive failure is happening. I will be in Shanghai next week and would like to get more information and observe the actual physical
specimens of your tests. Would this be possible?
Annie, Take Malcolm up on his offer to help you. This gentlemen is very wise and has experience that goes beyond explanation. The man is worth his weight in gold when it comes to the painting industry.
Malcolm, I have a project coming up similar to Annie's. We are using Polyaspartic plus paint chips broadcast over Polyurea coating. The difference is we are not spraying on the polyaspartic. We are using rollers instead. What kind of surface prep should we achieve on the polyurea to get good cohesion?
Polyaspartic Polyurea Resin/Hardener Manufacturer Overseas Biz Manager at Feiyang Novel Materials export@feiyang.com.cn
@Rene, is your project restoration or full new system? If new system, no special surface prep, usually, polyaspartic by rolling, cohesion would be no problem. How is your problem details.
Polyaspartic Polyurea Resin/Hardener Manufacturer Overseas Biz Manager at Feiyang Novel Materials export@feiyang.com.cn
@Malcolm, our customer locates in Shanghai, testing works in their lab, if you are in Shanghai, pls kindly let me know, they will contact you for this case, many thanks.
Annie, I arrived in Shanghai yesterday. I will be here until July 17th. I will call you.
Malcolm
Rene, To overcoat the polyurea you will need to sand it lightly to roughen it up a bit creating some profile for the polyaspartic to get adhesion to.
Malcolm
Nuclear Coatings Inspector Level II, Nace CIP3, C-3, Consultant
If I read the Pic’s correctly, The first, shows no surface irregularity, thus giving the top coat nothing to adhere to!
This would indicate that some type of prep for your mid coat may be required.
The 20 Micro on the spindle (The Pull off Dolly?) would be a cohesive failure, and could indicate that there may be a mix problem or an air entrainment into the mix? With out seeing the sample Pull off Test results first hand, you could take samples to a lab to have a test to evaluate the Manufacturers chemical analysis (Spectrum Analysis) pre mix, post mix, application, pre-cure and post cure.
Most coatings (heated or not) are applied by a 45:1 pump, Increasing the pump pressure to 70:1 as these are not ( I assume) 100% solids,( would not require the pump pressure), as this may in-train air into the mix. Over pressuring the materials would in-fact cause heat rise during delivery to the tip for mixing and heat sink during the delivery to the surface. This causes changes to the vehicle for the material, rapid changes that the materials after mixing, causes a void (normally atomized air) in the body of the film.These voids are filled with any gasses that are in the atmosphere in vapor phase and are readily absorbed into the film as the heated air escapes, thus reducing, the film integrity, and ability to achieve the required end test results.
Hopefully the problem has been resolved at this date and time. I see that I am about a month late.
Gerencia de Proyectos: Inspector Tecnico de Obras Montaje Industrial en GNL Quintero S.A.
Annie my opinion and while query is:
What type of polyurethane corresponds to the existing layer (type: acrylic or polyester), application time and thickness applied ??.
Now as the lining that you applied recently, thickness you mention (2000 microns) as you applied in one or two or more layers ?.
You sure that the existing film is polyurethane ???.
What type of surface preparation you made on the existing coat.
Apparently the loss of adhesion that you mention is present the effect of "(efforts adhesion) vs. (cohesion efforts)."
You checked the level of surface contamination of the existing paint.
Tony and David may be right, but there is something else to consider.
A polyurethane is the product of the reaction between a polyisocyanate and a polyol, forming a thermoset polymer. If an amine is used instead of a polyol, then a polyurea is formed instead. The main difference in properties between a polyurethane and a polyurea is the amount of hydrogen bonding. The polyurethane has one pendant hydrogen than can hydrogen bond with the carbonyl oxygen, while the polyurea has two. This leads to increased rigidity in a polyurea as long as other factors are the same. It also means that polyurea cohesive strength is enhanced at the expense of the adhesive strength being diminished. The level of hydrogen bonding in a polyurethane allows for higher hardness in low stress conditions and higher flexibility and tensile strength in high stress conditions than would otherwise be expected. The combination of hardness and flexibility gives the polyurethanes the toughness that provides significant advantages over other thermoset chemistries such as polyureas and epoxies.
The name polyaspartics has recently become popular among formulators in the industry due to the need to differentiate it from polyureas and polyurethanes. By definition, a polyaspartic is an aliphatic polyurea because it is the reaction of an aliphatic polyisocyanate with a polyaspartic ester - which is an aliphatic diamine. However, polyaspartic coatings are very different in both application and coating performance properties from conventional polyureas. For example, polyaspartics allow the formulator to control the rate of reaction and cure, thus, potlife of the two-component mixture can range from five minutes to two hours. While spray application techniques include the use of plural component spray equipment, many applications can be applied with conventional sprayers, making application much less complicated and less prone to error.
Bottom line - polyaspartics are polyureas with better application characteristices and polyureas as a class have poor adhestion characteristics due to their chemical structures. This means they have poor adhestion to the substrate and to themselves, and other coatings have poor adhesion to them. Adhesion is an issue, repairability is an issue, and compatibility with other coatings is an issue.
Depending on the length of static mixing line you may be cooking the pot life of the product prior to application thus diminishing the adhesive properties. Lower the heat on the supply lines and reapply / re-test.
It's the last line of James Hall's excellent technical summary that says it all for me.
In my experience with current polyaspartic primer/finishes, including their research and development, I'm surprised it's being applied over a polyurethane at all. Polyaspartic adhesion is usually best straight on to a blast cleaned profile for benign environments (up to C3 - ISO 12944), or over an approved zinc rich primer if we're talking about more aggressive environments - C4/C5.
Typical product technical data sheets also highlight the need for very thorough abrasion of polyaspartic if it is to be applied over itself, and I've been involved with 3 cases now of polyaspartic inter-coat adhesion failure and detachment. Does your paint supplier formally approve of its use over a polyurethane?
I'd certainly consult with the paint manufacturer involved, as to me, I'd be questioning the correctness of this specification, unless you have radically improved or advanced polyaspartic technology out there.
Finally, polyaspartic pot life is very sensitive to increase in relative humidity. Just check your environmentals at the time of spray application. Also, was it airless or conventional, as the latter could also give you some issues if the compressed air contained excess moisture. I'd always opt for airless spray with this technology.
Polyaspartic Polyurea Resin/Hardener Manufacturer Overseas Biz Manager at Feiyang Novel Materials export@feiyang.com.cn
Top Contributor
Hi, All, sorry, was on business trip last week.
@ David, thanks for your professional reply, "could indicate that there may be a mix problem or an air entrainment into the mix? " this is also reason that we suppose. As 2K Graco spraying equipment is mainly for quick 2K polyurethane, if apply polyaspartic spraying formulation, it must be problem of mixing completely.We are thinking two method:
1. Decrease viscosity through hardener, and additives.
2. Change longer mixing pipe of Graco 2K spraying equipment.
@ Alvaro, surely, mid coat is 100% polyurethane, but no pre-treatment on surface, as time is limited, after mid coat cure completely, top polyaspartic coat should be finished. We suppose no need to do surface treatment on mid coat, and it's not adhesion problem to mid coat, just cohesion in topcoat film itself.
Polyaspartic Polyurea Resin/Hardener Manufacturer Overseas Biz Manager at Feiyang Novel Materials export@feiyang.com.cn
Top Contributor
@ James, you offers good conception towards polyurethane, polyurea and polyaspartic.
Those three types is nowadays popular in protective coating. In my opinion, each types have it's own feature, depends on certain requirement of application. Sometimes, one type materials has good physical feature, but in certain application it would be disadvantage.
Finally, polyaspartic has good compatibility with epoxy, polyurethane and polyurea coat, but honestly adhesion to substrate is not so good as epoxy.
We need to clear feature of each materials, then can choice exact satisfied solution to project.
Polyaspartic Polyurea Resin/Hardener Manufacturer Overseas Biz Manager at Feiyang Novel Materials export@feiyang.com.cn
Top Contributor
@ Gary, thanks for your suggestion, actually we tried to change longer static mixing line, but it not possible, we hardly change construction equipment of end applicator. So now problem is we need to formulate another suitable formulation to fit this construction way.
Malcolm
Malcolm McNeil
Owner, McNeil Coatings Consultants, Inc.
Thank you, Robert. I appreciate your comments.
Rene
Rene Gameli-Kwame
Consultant/Business Developer
Malcolm, I have a project coming up similar to Annie's. We are using Polyaspartic plus paint chips broadcast over Polyurea coating. The difference is we are not spraying on the polyaspartic. We are using rollers instead. What kind of surface prep should we achieve on the polyurea to get good cohesion?
Annie Qing
Polyaspartic Polyurea Resin/Hardener Manufacturer Overseas Biz Manager at Feiyang Novel Materials export@feiyang.com.cn
@Regy we use right dolly.
Annie Qing
Polyaspartic Polyurea Resin/Hardener Manufacturer Overseas Biz Manager at Feiyang Novel Materials export@feiyang.com.cn
@Rene, is your project restoration or full new system? If new system, no special surface prep, usually, polyaspartic by rolling, cohesion would be no problem. How is your problem details.
Annie Qing
Polyaspartic Polyurea Resin/Hardener Manufacturer Overseas Biz Manager at Feiyang Novel Materials export@feiyang.com.cn
@Malcolm, our customer locates in Shanghai, testing works in their lab, if you are in Shanghai, pls kindly let me know, they will contact you for this case, many thanks.
Rene
Rene Gameli-Kwame
Consultant/Business Developer
@ Annie. This is a new application. Thanks for the feedback
Malcolm
Malcolm McNeil
Owner, McNeil Coatings Consultants, Inc.
Annie, I arrived in Shanghai yesterday. I will be here until July 17th. I will call you.
Malcolm
Rene, To overcoat the polyurea you will need to sand it lightly to roughen it up a bit creating some profile for the polyaspartic to get adhesion to.
Malcolm