I've been working on my L3 project that involves fiberglassing lengths of 8" Quik-tube/Sonotube. These tubes have yellow, waxy paper on the outside that interfere with good bonding of the epoxy/fiberglass. That will cause delamination problems and a compromise to the strength. To fix this, most people either sand off the paper or peel it off. This fixes the sticking problem, but it comes at a cost. The porous, fuzzy paper will now absorb epoxy like a sponge. All that extra epoxy does not do much at all for strength, but it does increase the weight of the tube tremendously. Plus, epoxy isn't cheap, and it's wasting money.
I've been looking at alternative ways to get over this problem. After a few experiments with chemical treatments, I think I've found the perfect solution; adhesion promoter. I'm now using Dupli-color Adhesion Promoter spray.
https://www.amazon.com/dp/B0007UAXJQ/?tag=skimlinks_replacement-20
From what I could find out, it seems the Dupli-color adhesion promoter is a chlorinated polyolefin in a mix of organic solvents which break up waxes/plastics/oils while the polyolefin provides a surface for molecular bonding between the paper and the epoxy while adding no noticeable weight (as was seen when measuring). Normally, polyolefins definitely do not allow epoxy to stick. However, the chlorination fixes this problem.
I applied two very wet coats of adhesion promoter to a 12" section of scrap Quik-tube (inner wax layer was peeled), and left it to dry. As a control, I peeled off the outer paper on another 12" scrap tube and left this untreated. After spraying the test piece and allowing to dry for an hour, no difference can be seen, but the surface has a slightly chalky feeling (might be in my imagination, though). The primer is mostly volatile solvent, so it did not add any weight to the scrap once dry.
Both scraps were epoxied with scraps of 6 oz. fiberglass for two wraps using US Composites 3:1 resin. End weights were compared.
Test Set:
Bare tube (inner wax lining peeled off): 19 g/in
Primed with adhesion promoter: 19 g/in
2 x layers 6 oz. fiberglass: 35 g/in
Control Set:
Bare tube (inner wax lining peeled off + outer paper peeled off): 13 g/in
Priming skipped...
2 x layers 6 oz. fiberglass: 41 g/in
The sprayed tube is significantly lighter per inch. The next tests were qualitative only.
Bubbles or delaminations:
Test: none seen
Control: none seen
Peel test:
Test: unable to peel off fiberglass without complete destruction of tube
Control: unable to peel off fiberglass without complete destruction of tube
Lateral compression was also crudely tested. Both took approximately the same amount of force to crush by squeezing. This is as expected.
I also scaled up and laminated a complete 48" tube, unpeeled, primed, and wrapped with 2 layers of 6 oz fiberglass. The weight came out very similar. There will be differences depending on how well excess epoxy is squeegeed out. The end result was the same; no bubbles or delaminations, and a much lighter tube than anticipated if the outer wrap was peeled off.
I tested a scrap 38 mm LOC MMT tube with glassine last night. Primed and wrapped. As of this morning, it looked like it stuck perfectly fine with no delamination. I'll inspect it more closely tonight since it's a bit tough to spot a potential bubble on a white tube. I'm hopeful.
Has anyone else tried adhesion promoter? I'm sold from now on every time I wrap.
I'd love for more experienced fiberglassers out there to test this and give feedback.
I've been looking at alternative ways to get over this problem. After a few experiments with chemical treatments, I think I've found the perfect solution; adhesion promoter. I'm now using Dupli-color Adhesion Promoter spray.
https://www.amazon.com/dp/B0007UAXJQ/?tag=skimlinks_replacement-20
From what I could find out, it seems the Dupli-color adhesion promoter is a chlorinated polyolefin in a mix of organic solvents which break up waxes/plastics/oils while the polyolefin provides a surface for molecular bonding between the paper and the epoxy while adding no noticeable weight (as was seen when measuring). Normally, polyolefins definitely do not allow epoxy to stick. However, the chlorination fixes this problem.
I applied two very wet coats of adhesion promoter to a 12" section of scrap Quik-tube (inner wax layer was peeled), and left it to dry. As a control, I peeled off the outer paper on another 12" scrap tube and left this untreated. After spraying the test piece and allowing to dry for an hour, no difference can be seen, but the surface has a slightly chalky feeling (might be in my imagination, though). The primer is mostly volatile solvent, so it did not add any weight to the scrap once dry.
Both scraps were epoxied with scraps of 6 oz. fiberglass for two wraps using US Composites 3:1 resin. End weights were compared.
Test Set:
Bare tube (inner wax lining peeled off): 19 g/in
Primed with adhesion promoter: 19 g/in
2 x layers 6 oz. fiberglass: 35 g/in
Control Set:
Bare tube (inner wax lining peeled off + outer paper peeled off): 13 g/in
Priming skipped...
2 x layers 6 oz. fiberglass: 41 g/in
The sprayed tube is significantly lighter per inch. The next tests were qualitative only.
Bubbles or delaminations:
Test: none seen
Control: none seen
Peel test:
Test: unable to peel off fiberglass without complete destruction of tube
Control: unable to peel off fiberglass without complete destruction of tube
Lateral compression was also crudely tested. Both took approximately the same amount of force to crush by squeezing. This is as expected.
I also scaled up and laminated a complete 48" tube, unpeeled, primed, and wrapped with 2 layers of 6 oz fiberglass. The weight came out very similar. There will be differences depending on how well excess epoxy is squeegeed out. The end result was the same; no bubbles or delaminations, and a much lighter tube than anticipated if the outer wrap was peeled off.
I tested a scrap 38 mm LOC MMT tube with glassine last night. Primed and wrapped. As of this morning, it looked like it stuck perfectly fine with no delamination. I'll inspect it more closely tonight since it's a bit tough to spot a potential bubble on a white tube. I'm hopeful.
Has anyone else tried adhesion promoter? I'm sold from now on every time I wrap.
I'd love for more experienced fiberglassers out there to test this and give feedback.
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