The most serious danger is probably the risk of fire from the incorrect handling of resins and catalyst. It has already been stated that catalyst and accelerator when mixed directly form an explosive mixture but as all resins are coal and oil base.
THEY ARE HIGHLY FLAMMABLE. SMOKING IN THE MOULDING SHOP IS TOTALLY FORBIDDEN.
Great care must be taken to mix the correct amount of catalyst to the resin to avoid a “HOT MIX” which could produce so much exotherm (heat) that it self-ignites. Any bucket of resin producing smoke should be immediately taken outside the moulding shop and filled with water, likewise any spillage should be diluted with water. Other fire hazards are solvent cleaners, styrene monomer and rags contaminated with flammable liquids. Small fires may be dealt with by Carbon Dioxide or Dry Powder extinguishers or by water spray.
Exotherm with time
All these materials are toxic if swallowed. Special care should be taken with catalyst as it is an organic peroxide and will cause burns to skin and possibly blindness if in contact with the eye. Readily available fire extinguishers of the correct type and patent eyewash should be at hand in the mould shop as well as a First Aid Kit in the yard office. The local hospital should be briefed at the beginning of operations about the nature of the chemicals being used in case of extreme emergencies as should Fire Services.
Occasionally some individuals show a skin reaction to handling glass reinforcements and more rarely to resins. Use of a patent barrier cream may allow the worker to continue but if the problem persists then transfer to another department should be considered. Rubber gloves can be worn but these tend to restrict manual dexterity and cause other skin problems if worn for long periods. Workshop ventilation should allow a complete air change 1–1.5 times per hour and an upper limit of 100 ppm (parts per million) of atmospheric styrene which evaporates during the gelation of resin. Face masks may offer some relief when laminating in confined areas and when grinding or sanding cured laminates.
It has been explained that heat is the agent which cures resin from the liquid to the solid state. Resins are designed and manufactured primarily for use in northern countries, and as tropical temperatures are higher, some effort will be needed to maintain a reasonable shelf life (storage life) of the raw material.
The source of resin for use in a developing country may be many thousands of kilometres away and delivery may involve a long sea voyage. This may expose the drums of resin to weeks of lying in direct sunlight on the deck of a cargo ship as such flammable cargoes are usually carried in well ventilated areas. It is essential therefore that the supplier despatches new stock to ensure that the exported resin arrives in the best possible condition. The duration between manufacture and use is termed shelf life. Often 6–12 months are quoted as the normal shelf life but resin can be considered useable as long as it is liquid. Three months for rotation of stock is a prudent period to aim for. Time spent in ports while the resin is being transhipped or awaiting customs clearance should not be overlooked.
Storage temperatures should not exceed 20°C as higher temperatures even for a few days will reduce shelf life. Resin specifically ordered for tropical use should contain a higher level of inhibitor in which case a higher storage temperature may be acceptable. Flashpoint is about 31°C.
On delivery the resin drums should be opened and checked for quality and contact made with the supplier and shipper if it is not up to expected standard. Following acceptance it will be the responsibility of the user and should be stored in as cool, shaded and ventilated place as possible.
All raw materials for FRP can be airfreighted. However, for reinforcements airfreight costs may soon outweigh the purchase price and for combustibles such as resin, accelerator and catalyst special airline approved containers will have to be used. This will require transfer from the manufacturer's container which will again add substantially to costs. The airfreight option is best avoided.
Reinforcement materials are supplied in rolls sealed in heavy duty polythene bags inside strong cardboard boxes. During handling these are prone to damage and on delivery the glass reinforcement should be checked for contamination by dirt, oil or water. If spoiled, the material is unusable. Once rolls have been checked they should be resealed to prevent contamination by high humidity.
The consequence of using damp reinforcement is that the bonding properties of the resin to the mat are reduced introducing the possibility of a weak interlaminar bond. It is for this reason that Classification Societies are reluctant to survey and classify new vessels built by yards in tropical climates except for those which have fully air conditioned moulding workshops or can show proof of moulding in a controlled environment.
The difficulties of arranging insurance for a vessel built without Classification Society approval has influenced the continued import of large FRP vessels by developing countries and partly explains why the advantage of low overheads has not been used to promote exports. Nevertheless boats are being produced and used successfully in the developing world.