[PSUBS-MAILIST] material question

[Alan via Personal_Submersibles]

Hi Ian,
a while since I looked at fibreglass, but I made my ambient from epoxy
rather than polyester because it was less hydroscopic apart from other
things. I used a marine epoxy, so I guess there are differing levels of
water resistance within the epoxy products.
Alan

Sent from my iPad

> On 10/05/2018, at 11:00 AM, irox via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
> 
> What Sean said.  Look up the spec sheets and you should get the water absorption rates and equilibrium.
> 
> Alan, I don't know much about GRP boat building (a little about surfboards), but it seems traditional to use polyester resin for this types of work.  Polyester is fairly low water absorbing, around 0.55%: 
> http://www.ndt.net/article/ndt-slovenia2013/papers/189.pdf
> 
> For comparison, some types of Nylon can absorb 3.5% mass in water (some are lower).
> 
> This 2009 paper on "Interaction of Water with Epoxy" indicates there is some swelling with epoxy:
> http://prod.sandia.gov/techlib/access-control.cgi/2009/094405.pdf
> 
> There a few different types of epoxy, I randomly picked "novolac epoxy" from the epoxy family, and found:
> https://hal.archives-ouvertes.fr/jpa-00251480/document
> After 10 days a 2.3% mass increase was observed.
> 
> Disclaimer: I didn't full read all publications I've linked to.
> 
> Cheers,
>   Ian.
> 
> 
> -----Original Message----- 
> From: Alan via Personal_Submersibles 
> Sent: May 9, 2018 2:39 PM 
> To: Personal Submersibles General Discussion 
> Subject: Re: [PSUBS-MAILIST] material question 
> 
> Hi Emile,
> my brother-in-laws fibreglass yacht has been sitting in the harbour
> for at least 30 years, so pretty impervious to water.
> The glass in the fibre would not crush, but the resin around it would squash
> a little under that pressure. I would think the resin would seal any exposed 
> fibres by squashing around them when put under that kind of pressure.
> What are you sending down that deep?
> Alan
> Sent from my iPad
> 
>> On 10/05/2018, at 5:34 AM, emile via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>> 
>> Hi All,
>>  
>> Material question:
>> Can prefabricated epoxy/glassfibre plate material (like PCB) withstand 5000M / 18.000Ft  presurised water?
>> Or will it be impregnated after a while?
>>  
>> Thanks in advance
>>  
>> met vriendelijke groet, with best regards
>>  
>> Emile D.L. van Essen
>>  
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