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8.1. At least one of three substances must be removed.
8.1. At least one of three substances must be removed. We have repeatedly explained, that three ingredients must exist for the "osmosis" to proceed: Water, styrene and uncured polyester. At least one of them must be permanently removed in order to prevent the "osmosis". 8.1.1. Moisture drying and acid wash out are not sufficient. Until now most repair systems have relied on moisture removal and even professionally treated hulls are very often only dried in the open air. This is not effective enough! Due to the moisture in the air a hull can not be dried to 100%. Besides it is not possible to water shield a hull totally. Thorough washing or even high pressure wet sand blasting does not always remove all of the aggressive acid "osmosis" residues. 8.1.2. Acid residues and styrene must be removed. To permanently cure "osmosis", all acid residues formed in the process must be eliminated as well as all remaining styrene enclosures in the underwater part of the laminate. Moisture removal is not too important as it will always return. Eventually remaining uncured polyester can not be hydrolysed without the presence of styrene.
8.2. Controlled thermal treatment the only solution. Extensive research has proven, that the only way to remove all "osmosis" causing factors is by the use of an adequately controlled thermal technology in combination with thorough fresh water washing. The fatal components will burst out or evaporate at temperatures low enough not to affect the remaining FRP other than in a positive way. A treatment of this type will also remove moisture and bring the uncured polyester to cure. The two possible treatments so far known are the infrared heater (IR) and the HYAB OsmoLance. Note! It is extremely difficult to obtain the 70 - 80°C laminate temperature needed without deformation of the hull, when IR is used. The HYAB OsmoLance, used by a certified operator, causes no such problems. 8.2.1. Many negative "specialist" opinions scare operators from the use of IR. Specialists on FRP often warn against the use of IR-heating. They claim a destructive effect on the strength of the material and that so much heat accumulates, that deformations may occur. The destructive effect is sheer nonsense and opposite to reality.
The deformation risk is, however, very relevant. As soon as no
styrene and moisture remain in the hull, the temperature within
minutes will rise to dangerous levels. Unfortunately some manufacturers, to be on the safe side, claim 50ºC to be the maximum. This has caused a widespread rumour among boatyard people, that higher temperatures destroy the laminate. Most of them do not dare to let the IR equipment heat an "osmosis" hull to the 70-80ºC necessary for the styrene enclosures to break up the skin of uncured resin around them. Then, at this temperature, the enclosures will cure, using part of the styrene. The remaining styrene evaporates and if one succeeds in removing also the acids, the "osmosis" process can not start again, even if water should enter. Just heating of the surface normally causes moisture to move inward against the cooler inside instead of leaving the material. By proper IR heating instead the evaporating styrene causes an alternating cooling / heating cycle, which makes also moisture and at least part of the acid to evaporate. The rumors about laminate damages and about forcing moisture inwards have caused many operators to abstain from the use of IR-heating or other types of heating equipment. 8.2.2. English yards report less recurrences. It is observed, that yards in England have less repair failures than others or less than 10% instead of sometimes more than 50%. The only apparent difference is, that due to the climate most
English yards tend to use IR-heaters for the drying. Beside the small average size of the hulls and the cold climate, the reason for the positive results most likely is the use of the IR heating. 8.2.3. IR heating is unsuitable only for sound FRP. The warnings about IR-heat originate from laboratory tests of sound FRP, where the loss of strength during extended IR-heating is caused by the coefficient of expansion differences between the fibreglass and the polyester. This loosens the bond between the two materials. 8.2.4. 120ºC heat only causes max. 5% loss of strength. Tests commissioned by HYAB at the Delft Rubber and Plastic Research Institute show that there is no loss of strength in sound FRP after heating to 80ºC and only 5% after heating to 120ºC. However a boat hull should never be heated over 70ºC other than spot wise during efficient cooling of the surrounding areas in order to avoid deformations. 8.2.5. Early "osmosis" stage causes 30% loss of strength. In "osmosis" affected FRP a major loss of bonding is already caused by the alkalis. Moderate heating does not make it worse Our tests show instead an increased strength when the IR-heating is used on "osmosis" affected FRP. 8.2.6. Tests prove that heat restores the strength The tests performed at the Delft test institute prove, that the bonding is restored to original strength in the HYAB treated test samples. Other HYAB tests shows that the controlled heat makes the alkaline residues act as a cement. Properly used IR-heating probably has a similar effect. 8.2.7. IR heating different on "osmosis" and sound FRP. When used on sound laminates IR equipment causes heat to accumulate in the material which is very difficult to control and deformations are apt to occur. An "osmosis" affected laminate has a substantial content of free styrene, which at about 60ºC
starts to vaporise and move to the surface. There it evaporates
and cools the surface. The IR-heat forms a steady warm air stream which rises along the hull and absorbs the evaporating fluids. During this phase the surface is shielded from the heat by the evaporation. As a result the laminate cools down and vaporisation of the styrene ceases, allowing the heat to reach the hull again. When a suitable number of heaters are used, this reciprocal action will continue without raising the temperature over 80ºC, as long as any styrene exists. The styrene smell is very obvious, and therefore it is easy to determine when styrene is gone and to disconnect the heaters. It is essential that the heaters are not kept on for too long after the completed styrene evaporation to avoid deformation of the hull. If it is not a type 3 or a severe type 2 "osmosis", the moisture and hopefully the acids will evaporate together with the styrene. With no styrene left there can be no more "osmosis" process, even if water should re-enter, but still there is a risk, that the FRP contains contaminants of the acid residues. If such residues attack cured polyester, new styrene is released and the "osmosis" can start again. 8.2.8. Repeated washing needed during the IR treatment. The upward air stream caused by the heaters is not strong enough to absorb all of the evaporating fluids. Some of them, especially the acids, dry instead on the hull surface and block further evaporation. Therefore the hull must be washed every 2 - 3 days during the IR-drying phase. The best result is achieved when cold water with a dash of caustic soda is applied with a sponge. High pressure steam cleaning once a week is also recommended, if equipment is available, in order to wash glycol out of the outer layers. The glycol has too high a boiling point to evaporate together with other fluids. Even if it has no influence on the "osmosis" process, such glycol near the surface may affect the moisture meter enough for a surveyor not to approve the repair. It may also affect the binding of the epoxy coats to the polyester. 8.2.9. IR is often avoided due to the high current cost. IR-heating is very expensive! A 30´ hull needs at least 6 kW for
2 - 3 weeks for optimal performance. This is another reason why
IR-heating is not used in warm climat Most yard operators lack the necessary knowledge about the nature of the "osmosis" process and are not aware, that more than the moisture must be removed out of the hull. Their customers are therefore offered the cheaper open air drying Since no complete "osmosis" know-how and no practical means have been available, frequent errors due to insufficient treatment are claimed to be inexplicable. 8.2.10. The HYAB OsmoLance is faster and safer than IR. The HYAB research has made it possible to create a special heat treatment tool, the OsmoLance, exactly designed and balanced for "osmosis" repair. The OsmoLance works along the same physical laws as the IR on "osmosis" FRP, but it does not create accumulating heat and it does not affect sound FRP. The OsmoLance works in minutes where the IR needs weeks and the operator always can control that all harmful substances are removed.
8.3. Voids in treated laminate must be restored. Most popular "osmosis" repair methods do not consider the substantial amount of dry and open capillaries and dry fibreglass cavities left inside the repaired laminate. The epoxy water shield is merely expected to prevent any further moisture from entering into the cavities. 8.3.1. Only water shield and filler are not sufficient. The water shielding epoxies shield only the outside of the underwater hull. If the laminate has not been heated over 75ºC, the loss of binding between fibreglass and polyester, caused by the "osmosis", will provide wide capillaries right through the material. Water from condensation on the inside and water seeping down from uncovered but often wet areas above the waterline will easily accumulate in the cavities. Even if styrene and acids are properly removed and therefore no new "osmosis" process can start, the water will cause further loss of binding and strength. In a cold climate it will freeze and cause de-laminations. Nor can the loss of strength caused by the cavities be restored by the shielding epoxy. 8.3.2. An epoxy with low surface tension must be applied. Before filling or water shielding, a penetrating epoxy resin must be applied for re-lamination purpose. Should a special penetrator without solvents not be available, at least a normal solvent free laminating epoxy with a slow hardener must be used. Then preferably applied late in the afternoon, to avoid high temperatures. Penetrating epoxy resin is to be applied in two layers with a mohair roller and constantly treated with a wide rubber scraper, until the trickle stops. The second layer is applied as soon as the first has soaked into the laminate and the surface looks dry. Check for sure that the epoxy has no solvent content.
8.4. Epoxy resins develop an oily "skin" when curing. Most epoxy resins used for "osmosis" repair have an amine type hardener. The amine reacts with carbon dioxide in the air and forms an "oily" skin of amine carbonate on the surface during the curing. After some time this skin hardens and affects the bonding of further epoxy coats. 8.4.1. New coats must be applied within specified time. As long as a coat stays tacky, a roller or brush will break up the skin and let the next coat stick properly. For the types used in "osmosis" repair tacky periods of 18 - 36 hours are normal. Some special penetrators are able to stay tacky for up to 72 hours if the temperature does not exceed 20º C. 8.4.2. Wash with citric acid if tacky period is exceeded. If for any reason the filler or the next coat can not be applied during the tacky period, the surface first must be sanded and / or washed with 5-10% citric acid or vinegar solution. 8.4.3. Spray gun application needs wash between coats. The spray gun is unable to break the amine carbonate. Therefore, if the water shield is to be sprayed, a hardener providing shorter tacky period must be used and the surface washed with citric acid or vinegar solution between each coat.
8.5. Never apply the filler directly to the polyester. The filler must be of epoxy type and preferably of the same brand
as the underneath material to avoid curing faults. Only apply filler between two epoxy coats. Do not apply penetrator or eventually water shield on bigger areas than what can be filled within the tacky period.
8.6. Avoid the use of tar epoxy for the watershielding. There are lots of products specially developed for "osmosis" treatment on the market. Most are more effective and less toxic than the earlier used tar epoxy and may be transparent or non-transparent. Often they are available in two or more colours to provide for a sanding control. Note! Skull marked products contain tar or other poisonous phenol type accelerators and are also less water tight than higher quality epoxies!
8.7. Resin and hardener must be exactly measured. It is essential for all types of epoxy that hardener and resin are mixed exactly as the manufacturer prescribes. Even slight differences may cause the epoxy coat to become too hard or too soft . Surplus resin or hardener always cause uncured spots in the coat. 8.7.1. Never mix by hand bigger quantities than 1 lit.! For bigger amounts a winged shaft and a drilling machine must be used. 8.7.2. Mixed epoxy must be protected against sun heat. Mixed quantities of more than 5 lit. must be protected against the sun and stored in wide pots. Preferably they should be divided into several pots, to avoid an uncontrolled and immediate curing. Chose a high quality epoxy! Epoxies like polyester need an accelerator beside a hardener in order to cure properly. In order to keep the costs down, many marine epoxies use cheap tar-, nonyl- or other phenol based accelerators which count for 25-50% of the total resin volume! The water penetration ratio of such epoxies is double or higher than for an epoxy with a low volume, phenol free accelerator. Further phenol is classified as poisonous. Most epoxy manufacturers us!e the water absorption ratio as a quality proofing This figure is normally 0.4 - 0.6
% for epoxy irrespective of accelerator and up to 5% for polyester
and explains the amount of moisture the material can absorb and
keep. Thus the epoxy manufacturers claim their products to give at least 10 times better protection against water penetration than polyester gel coat. This is false! A low quality phenol type epoxy without special water shielding additives does not give better penetration protection than a good polyester gel coat and a high quality epoxy perhaps twice the protection. The difference depends more upon the faster break down of the gel coat which after some years can loose all protection properties whereas the epoxies stay stable. 8.7.3. Two different types of "high build" epoxy. "High build" means, that solids are added to the resin. One reason for this is to provide the possibility of using it as a "roll on" filler where a few layers are thick enough to be sanded to a perfect surface. Then the solids must be easy to sand and the moisture protection is poor. Another type is the water shield high build which is significantly higher priced. Here the solids consist of materials, mostly overlapping flakes, which make it more difficult for the water to pass through. The flakes commonly consist of high molecular solid epoxy. They
are transparent and not visible in a transparent resin. Chose highest quality irrespective of price. Take a thin expensive latex preservative and a thick cheap one. Blow them up like balloons and leave them for some days. The thin one will keep the air, the thick one will have lost a lot! It is the same with epoxy. Two layers of the high quality will give better protection than 6 layers of the cheap one.
8.8. There are no "osmosis" shortcuts. The complexity of the "osmosis" makes every case different and the price for a proper repair will vary within large limits. No serious operator can tell more than a very approximate figure without a close examination. Even then he must include an extra charge for the repair of eventual de- laminations 8.8.1. Boat owners should be warned about cheap repair. Do not try to slow down the "osmosis"-process by just sanding and applying an epoxy water shield, if a proper treatment cannot be afforded at the moment! The "osmosis" will proceed anyway and a later proper repair will become more expensive due to the necessary removal of the epoxy coat. 8.8.2. The pthtalic acid is aggressive, but the water is not. If a proper treatment can not be afford for the moment, just open the blisters and avoid any filling or water shielding! More water entering into the laminate will dilute the acid and make it less aggressive. The damages will be less severe and a later treatment less expensive than if a water shield is applied.
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