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Right material for repeated salt water submersion

Posted by Calsa 
Right material for repeated salt water submersion
July 27, 2019 10:28PM
Hi all,

I am getting ready to build a custom Skeg (think rudder, but, well not!) for a sea kayak. Plenty of info exists on UV degredation, but I have not found much on what salt water submersion will do to filliments. I hate to get far from shore and have a blade break due to unexpected effects on the material.

Beyond the obvious hydroscopic absorbtion (*cough* PLA, *cough* Nylon) I want to understand other issues others may have encountered.

Does saline actually react with any common material (PLA, ABS, PETx, TPU/E, Nylon, PC,) ?

Has anyone printed parts that were both submerged in the ocean or salt water but also exposed to high UV (when not under water)? If so what did you use and how well did it hold up?

The goal of this is to find a materials that are very rigid, low warp, but also the least reactive to UV + saline?
Re: Right material for repeated salt water submersion
July 28, 2019 04:24AM
I think it would be a wise idea to cover your printed part with a certain type of epoxy resin that is also used for surfboards. Because prints are always pretty susceptible to water. The surface area is also greatly increased because of the edges of the layers which doesn't help in this case of submersion.

So I would suggest using at least ABS or PC with an epoxy resin coat. But I can't back this up with any hard data.

Edited 1 time(s). Last edit at 07/28/2019 04:25AM by Ohmarinus.

Re: Right material for repeated salt water submersion
July 28, 2019 06:16AM
... "vapour-smoothing" the surface could help to close gaps and reduce surface area.

PET or HDPE should be good materials - but then the surface smoothing could be a problem ...

Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]
Re: Right material for repeated salt water submersion
July 30, 2019 07:13PM
You may want to investigate the following materials to see if any of them might be what you are looking for. All of these have come as samples from the Maker Box Explorer subscription and some of the packaging says weather resistance or resistant to water/moisture.

ASA - Similar to ABS, but with better weather resistance.

Fluorinar-C Kynar PVDF - Excellent toughness and abrasion resistance, extreme chemical compatibility, zero flame propagation, resistance to UV and ionizing radiation, high temperature use up to 150C.

Alfapro-BETA RELEASE - Resistant to high temperatures, UV resistant, resistant to hydrolysis (moisture), elevate performance and impact resistant, sandable and post workable

PC+PBT - Superior stiffness, ductility balance, great structural integrity and drop impact performance, excellent fatigue performance, high chemical resistance to motor oil and grease.

All of the above statements are printed on the package samples of each filament.

I have a few items that I've printed in Flourinar-C Kynar PVDF and the Alfapro-BETA RELEASE filaments that are living outside in the Florida sun/rain 24/7. The Alfapro-BETA RELEASE was white, but the object is now a dirty white/yellow color but is structurally sound as it holds part of my flag to the pole. I forget exactly which month each sample came, but it might be alternative avenues to look for materials that resist saltwater.
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