Adhesive for Stainless Screws in HDPE

[my1stbenz]

I built a swim platform for my Sea Ray and used King Starboard(HDPE) for the decking material with a 304 stainless structure. I didn't want any visible fasteners so I tried using #12 Stainless wood screws from the underneath into the bottom of the deck. Overtime, these screws slowly work themselves free(not stripped). SO before I go the route of using screw inserts, I am curious if I could try an adhesive/thread-lock route first.

The obvious issue is HDPE is a low surface energy plastic which makes adhesives a challenge. I am curious if any of you fellas have a recommendation?

 

[97prizm]

I'm going to suggest an epoxy made for plastics.
A few recommendations that I found were,
"Use through-bolts, plastic-safe threadlockers (like medium-strength blue or CA glue), or threaded inserts. Avoid over-tightening, which strips the soft plastic."
Loctite 425 is specifically for fasteners in plastics.

 

[my1stbenz]

I ordered some Loctite 770 primer and some 425 from Grainger. I'll give it a try and report back on the results.

Thanks!

 

[kschachn]

The obvious issue is HDPE is a low surface energy plastic which makes adhesives a challenge. I am curious if any of you fellas have a recommendation?

As you note, nothing is going to stick to such a material without some kind of surface modification. I wouldn't expect much no matter what.

 

[my1stbenz]

As you note, nothing is going to stick to such a material without some kind of surface modification. I wouldn't expect much no matter what.

I will flame the plastic before I prime. That’s about the best I can do. I had some luck with that when I used this board on another project and sealed a butt joint with 3m 4200. Noticeably improved bonding.

 

[97prizm]

I will flame the plastic before I prime. That’s about the best I can do. I had some luck with that when I used this board on another project and sealed a butt joint with 3m 4200. Noticeably improved bonding.

What about just going ahead with through bolts? Sounds like the best option.

 

[my1stbenz]

What about just going ahead with through bolts? Sounds like the best option.

Plan c. Plan B is inserts. I really don’t want to see fasteners in my platform surface.