Gelcoat

Machining damages the surface, destroys coatings and gelcoats if they exist and, to avoid the risks of later attack, it is sometimes necessary to (gel)coat after machining. 

Ammonium polyphosphate AP420 series Clariant (Germany) Intumescent gelcoats (epoxy, UP, or PUR based)... 

General Industrial, Coil Wood Products Colorants Gelcoats Furniture Protection Plans... 

Physical changes that can be expected to occur at the accelerated condition but would not be considered significant include failure to meet acceptance criteria for dissolution for 12 units of a gelatin capsule or gelcoated tablet if the failure can be unequivocally attributed to cross-linking. 

A range of antibacterial products recently developed, are announced and described. The first is a polyester gelcoat incorporating Microban antibacterial agent, called Maxguard AB the second is a masteibatch called Neutrabac, which is particularly suited to PP and PE compounds and the third is a new antimicrobial sheet based on an antimicrobial masteibatch, called Actifresh. NESTE POLYESTER VICTOR INTERNATIONAL PLASTICS LTD. ROYALITE PLASTICS LTD. 

Sterpon. [Convert SA] Unsaturated polyester resins and gelcoats. 

Crystic . [Scott Bader] Thermoset polyester resins for aircraft industry moldings, in elec, industry for switchgear, generator insulation, in chemical ii us-tty for chimneys, ducting, pipes, for building, land transport, boat hulls, GRP, filament winding, extrusion, gelcoat applies. 

Spray guns are available for gelcoat, chopper, saturator and flow coater, at outputs of 3.6-9 kg (8-20 lb)/min resin, 1.8 kg (41b)/min glass two-strand chopper, or 1.1 kg (2.61b)/min one-strand chopper, giving a total laminate deposition of 5.4 kg (12 lb)/min with two strands. Air consumption is 9-10 ft /min. For higher volumes, four- and six-strand choppers are also available, dispensing 17-19 kg/min resin and 33% glass content. 

Resin lamination should not be carried out at a temperature of less than 20C (68F). A catalyzed/promoted resin is heat-sensitive and catalyst levels should be adjusted to varying temperature as recommended by the manufacturer. With resin laminating, where space is limited, mold preparation such as releasing and gelcoating can be done in a tent made of polyethylene film (which can also be used as a warm area for curing resins in cold weather). 

Present day developments include Lotus for production of car bodies, the female mold half is first coated with a gelcoat and dry reinforcement (mainly continuous filament mat and some woven roving) and PUR foam formers are placed on it. The foam inserts have previously been wrapped in continuous filament mat to create a stiff torsion box on each side. The inner male mold, with an airtight peripheral seal, is then placed over the loaded mold and bolted in place and resin is then drawn evenly into the mold by vacuum. 

A gelcoat can be incorporated as necessary, applied 100 pm thick to the carrier film. Thin gauge film (19 pm) is used once thicker gauge (38 pm) is reused (some manufacturers are known to reuse 5-6 times). The line speed at an average product weight of 1 kg/m x 0.5 mm thick is up to 24 m/min for 4 kg/m x 3.0 mm the speed is 5-10 m/min. 

Pinholing Small bubbles of air trapped in the gelcoat before gelling also when resin is too viscous or too-high filler content or when gelcoat wets release agent imperfectly... 

Spotting Small spots all over gelcoat surface Usually due to inaccurate dispensing of one ingredient of the resin formulation. 

Fiber pattern Pattern of fiber reinforcement is visible through gelcoat or prominent on surface Usually when gelcoat is too thin or reinforcement is laid up and rolled before gelcoat has hardened sufficiently or molding demolded too early. Does not usually affect performance but can be unsightly. 

Star cracking Over-thick gelcoat occurs when laminate receives reverse impact gelcoat should never be more than 0.4 mm (0.016 in) thick. 

With RTSs, any loose resin and reinforcement should be removed and the affected area cleaned and dried. It may be useful to roughen surrounding areas, to obtain better adhesion. For superficial damage (to gelcoat only), apply catalyzed/activated resin to the damaged area and allow to set/solidify. Film, such as transparent ceUulose, tape or TP polyester, may be used to keep the resin in position and impart a smooth surface finish. Apply a thicker film of resin than usual, to allow for shrinkage. When the repair patch has fully hardened, dress the resin back to the correct contour of the molding. 

Powdered mineral fillers tend to increase compressive strength, hardness and modulus of the compound. However, when used in large amounts, there is a considerable reduction in bending strength. Fibrous fillers are used to increase tensile and impact strength. Surface properties of moldings can be improved by use of a suitable powdered mineral in the gelcoat only. Powdered quartz or zircon in the gel coat can improve hardness and abrasion resistance. Properties, which may be selectively altered by use of fillers, include ... 

---