Osmosis in grp

I am very new to sailing and am writing to you as I have read articles on osmosis in GRP. I am shocked and surprised to hear that the composites are so poorly chemically-bonded together. In fact they seem to form an interference fit where the reinforcement is encapsulated but will allow water to penetrate between the resin and reinforcement.

I operate a company that produces primers, tie coats and bonding agents for glass, aramid (kevlar), carbon fibre etc etc. These are used to bond the reinforcement to rubbers for flexible composites. The composites are used for high spec uses such as aircraft door seals, turbo charger hoses, belting (e.g. timing belts) and need to form a complete chemical bond to survive. In forming this bond, the composites resist water immersion indefinitely and the part would wear out rather than fail through bisbondment.

Some years ago, I developed products designed for the rigid composite market and had not considered boats but turbine blades. I tried to get the project off the ground and approached the NW Composite Centre, meeting with a professor, to test the improved strength. The project stalled however as there seems to be an attitude that composites are a superior product and that there is no improvement necessary.

I am trying to gauge if there is an interest in bonding glass to polyester. The resulting product should be tougher as the fibres will not slip within the resin. The original idea was to produce thinner turbine blades that were larger but of the same strength of smaller blades. More electric could be generated per foundation. The end product for boats could also use cheaper orthophthalic polyester resin as the interface will be less susceptible to water. The product should also last much longer and have higher impact resistance.

I can also bond a wear resistant film on hulls using UHMWPE or kevlar, which will have much higher abrasion resistance if being dragged up a beach for example. Impact resistant coatings of kevlar could also be bonded to critical parts of a grp hull, since glass has such poor impact resistance.

I would be grateful for feedback on if these products are of any interest.

 

With the cost differential between polyester, vinylester, epoxy resins becoming narrower in recent years, there would have been more money in this 15 years ago than at present.

 

Thanks FMS for posting a reply. It is my fault for not explaining all the benefits, but using a cheaper resin system is just one advantage. For example; there are many holes drilled through the hull and cabins for fittings. These need to be sealed carefully to prevent water ingress. Many posted comments are concerned about the effects of water in grp, which is reflected in the reduced price of older boats (poorer design is also an aspect). With flexible reinforcements (hose, belt, seals etc) the reinforcement needs to be bonded to the polymer to obtain the full advantage and improve longevity of the component. Chafing through movement is not really a factor with rigid composites, but poor bonding/the lack of bonding manifests itself through poor water resistance, water wicking along the glass, lower impact resistance etc. The result is seen as blistering or cracking. I wanted to test the water with these ideas after reading concerns of grp boat owners and prospective buyers. Any comments would be welcome.

 

Greg,

The primary concern with water intrusion into grp hulls at fittings and holes is not with water into the grp, but into the core. Most boats are built with either a foam, or wooden core surrounded by a fiberglass shell. Whatever the core material though, water intrusion is deadly to the core, and can relatively quickly rot the material, either through fungus, or hydrostatic forces. In this application a better skin material doesn't really help since it is rarely the skin that has problems.

A grp material that could replace epoxy/vinyl/poly that is completely water proof would be very interesting, though it would take some independent testing to convince the market. That being said, the first application I would see would be as a barrier coat on the outside of hulls. This is typically done over gel coat to provide a water proof base for bottom paint, and if your material could be shown to eliminate, or even reduce the incidence of blisters could go a long way to opening the market for other applications.

 

Greg... I need to purchase some very long length timing belts of the type you are describing. However, you have your profile set not to receive PMs or emails from members.

Could you change that setting or advise me where to purchase your product?

Thank you.

 

Impact resistant coatings of kevlar could also be bonded to critical parts of a grp hull, since glass has such poor impact resistance.

You should rethink about what you have written because you sure as hell dont understand glass very well !!! maybe been reading the wrong books !! Have you ever got you hands dirty and actually built anything from resin and Glass ??
I would trust my life on a glass up that i had myself built .
Nothing fancy ,two types of glass !! just plain off the shelf products that can be bought over the counter and only use polyester resin to boot !!!
When you use and understand glass and what it is capable of then you might change you mind about impact and Twist and flex and progresive distructing laminates specaily built for life saving equipment thats used in exstreme conditions .
What a dumb statement !!

 

By you me thinks

Thou it wasn't especially mentioned it's obviously compared to kevlar bcs it's in the same sentence..
BR Teddy

 

gregbond, all of the products and research you have mentioned could have direct application in hovercraft construction (fans, belts, hulls). Since the UK is the historic epicenter of hovercraft technology, you are in a good position to take advantage of it.

I once did something stupid on one of my old cars in the rocker panel. I stuffed a hole with partially shredded fiberglass scrap, and draped the opening with a fiberglass cloth piece. I then brushed some polyester over the top piece. I may have put a thin layer of body filler over it, cannot recall exactly, it was a long time ago. A year later I opened up the rocker panel area to fix it right this time. Much to my surprise the glass was soaked with water. This is how I learned fiberglass soaks up water, I honestly did not know this before hand.

It seems to me that stronger bonds are a good idea, but a base material which does not soak up water would be another good idea. I suggest this not so that unresined areas could go unfinished (or do stupid things like me), but so that moisture cannot migrate within the shell. I don't know if this is an existing problem outside of damaged areas, just tossing an idea out there.

 

The bonding agents I mention are supplied to coaters/dippers that supply belt manufacturers or manufacturers that also dip/coat. The belt used will depend on the environment & properties needed i.e. - av. temp., min. temp., max. temp. (usually most important), oil (or fuel or acid or alkali or chemical) resistance, expected durability, tension, etc. If you need a long belt for an engine, then Gates power transmission or Continental should be able to help. These are constructed from high temp composites to resist fuel and oil. If you need a moderate temp resistance (130'C max) for machinery, then a polyurethane belt may be sufficient. Many manufacturers can make a bespoke belt by using a PU reinforced backing and bonding teeth onto the backing. Hope this helps.

 

Thanks for posting Stumble. These fillings can also be bonded to the outer resins, usually cheaper than using epoxy systems. This would reduce the problem of water ingress. The only issue I can forsee is that the balsa or PU foam could shear under too much movement - and I'm only thinking of small movements.

Re. totaly waterproof - that's not likely given the small molecular size of H2O. Water is likely to permeate through any grp. However, the glass is encapsulated rather than bonded, which leaves an opportunity for water to exploit. Any imperfections will be found and eventually even good quality fabrication will be weakened. Bonding the glass (i.e. chemically bonding the glass to the resin rather than coating/encapsulating the glass), I think would reduce imperfections and increase longevity.

 

Thanks Tunnels for your constructive comments. Glass is a wonderful product - readily available and cheap. When spun thin enough, it is even flexible, but it's still glass and believe me, it does break under impact when held in a composite. Glass is not for example used in hose outer layers due to its' low impact resistance (compared to steel, polyester and other reinforcements). Glass will also shatter in grp under an impact, but the breaks are not that evident as the rigid resin usually still holds it together. Reliant Robin owners will attest to the fact that grp cracks after impacts (hope I've not insulted another group). Every material has its' limitations and I'm not giving glass a bad rep., but I'm exploring if it can be improved.

 

Thanks Kach 22i. I've worked on hovercraft skirts before. They need to withstand low tech. standard environmental conditions - 70 to 90'C max (black in sun), -10'C (rubber becomes v. stiff), UV resistance and water resistance. Rubber (usually NR - natural rubber) withstands wear well and gets time to dry out. NR is quite impervious to water, but even NR 'blooms' ingredients to the surface - e.g. sulphur.

The rocker cover is an interesting anecdote. Water will always get to the resin/glass interface.

My supposition was that if this interface was bonded, it would be much more difficult to separate and be stronger. Epoxies are a reasonable product for bonding and give a chemical bond to many surfaces, but not glass. Polyester and vinyl resins also do not bond glass.

Other than our products, I do not know of anything else that bonds to glass other than silane. Silanes (there are many types) sound great in theory and are used to form scratch resistant lenses for example as they are also very tough. However, in practice, they have a very critical application amount and need to be applied to a level of one molecule. You can appreciate that this is quite difficult to achieve even in factory conditions. Too little and a patchy poor bond is seen, too much and the silane layers, producing a friable, weak layer. Silanes also need to be applied, left to react with water, then dried, then bonded soon afterwards. Too many ifs and buts means they are only suitable for mechanised production.

Our product is applied (brush, roller, spray), dried, and left until ready for use. The coaters normally thin the products down and dip, then dry, roll up and send this to the manufacturer. Weeks or months later (stored in a standard warehouse at room temp), it is bonded up.

Up until recently, I thought there was a glass primer for GRP, but due to my recent interest in boats and hearing about the problems, I was surprised to find there isn't anything bonding the glass to resin. I thought, "well, no wonder it blisters". Maybe there isn't enough interest though and perhaps grp users are happy to carry on as is. I'll gauge this from this blog and other contacts.

 

You might be interested in Post #8, the GE blade, an old post of mine back in 2007.

Link:
http://www.physicsforums.com/showthread.php?t=176887

gregbond, I do not see a homepage or website listed for you. What is your company name?

 

Thanks kach22i. Watched the videos of your hovercraft on Youtube - everyone should have one. Vintage Porche as well? - your living my life.

Those blades are a work of art. Glass is mentioned in one rotor design. Some fabrics perform well under stress and glass is one of them. It is used as the 'backbone' in some belts to prevent elongation. Some fabrics perform poorly under compression. I'm not an expert on fabrics, but I believe this is true for aramid. Most Carbon fibre is supplied pre-coated with epoxy I believe. In most cases, this gives excellent performance. However, the epoxy molecule is quite large compared to other reactive groups that can be used. The result is a lower density of bond sites, mostly due to steric hindrance. Epoxies are also more brittle and not as 'tough' as other materials - i.e. they perform poorly on sharp, focused impact and have little 'give'. When I analysed failures of carbon fibre results, the fibres seemed to have pulled out of the resin. The resin had shattered once its' max load was exceeded and the C fibre separated. Part of the bond strength analysis is quantative (peel strength) and part is looking at the mode of failure. Arguably, the latter is more important as it indicates if the composite will fail rapidly and will withstand stress & strain over long periods i.e. catastrophic failure & longevity. I wonder what happens when the engines are reversed - how hot do these blades get I wonder?

I started the thread to see if there was an interest, but wasn't intending to promote my company. Would I be breaking any rules of the blog if I listed it?

I will try to alter my profile later to receive mail.

 

As far as I know, a link in your signature or profile is okay. If you elect to remain a man of mystery, that is okay too.

One of the yacht design forums will not even allow you you hint about products or services, no links allowed even if it is part of the discussion. This forum is not like that, and few have ever abused it. There is a Press Release area in which announcements should be located, some threads get moved there, but not very often.

RE: Videos; I've done my share of floundering in public with each step of my hovercraft experiments. Been a few years since I've posted anything.