JEC COMPOSITES MAGAZINE - Issue #38 - January/February 2008 - 45

Gelcoats Tab.1: Mechanical properties of CrysticLS30PA (LDs post-cure) Mechanical data Property Tensile elongation Tensile strength Flexural modulus Barcol hardness Water absorption, 4 weeks at 23°C Heat deflection temperature (1.80MPa) Unit % MPa MPa mg °C LS30PA 2.8 52 3045 47 64.7 62 Fig.6: Panel without 5000PA Fig.7: Panel with 5000PA What is Crystic Crestacoat 5000PA? Crystic Crestacoat 5000PA is based on innovative urethane acrylate technology that is unique to Scott Bader. This unique formulation has outperformed both polyester and vinylester barrier coats in surface finish assessments. It was designed to be applied either by spray or brush. Because it is lightweight, only 600g/m2 is required to meet the recommended 1-mm-thick layer. It can be applied either to the gelcoat of the mould to improve the mould surface, or behind the gelcoat of the part. Either way, it will ultimately improve the surface finish. Crystic Crestacoat 5000PA was also subjected to a rigorous regime of weathering, blistering, mechanical, and liquidproperty tests, although wave-scanning was the main area of interest and testing for this product. Liquid properties and handling It is very important that any product supplied to customers have good handling properties. Therefore, the liquid properties must be optimised. The results in table 2 below show that Crystic LS30PA has typical spray liquid properties. These possess the correct conditions for spray products, and minimise sag and any porosity issues associated with spray gelcoats. Tab.2: Liquid properties of Crystic LS30PA Liquid data Property Viscosity at 4500 s-1 Viscosity at 0.6s-1 Specific gravity Gel time at 25°C, 2% Butanox M50 Flash point Unit poise poise °C LS30PA 2.4 250 1.2 7 26 Weathering and blistering Using Crystic Crestacoat 5000PA in parts has no negative effects on the weathering; because it is used behind the gelcoat, it is not affected by direct sunlight. A 12-month check was nevertheless performed. A 12-month blistering test was also performed, here again, with no negative effects on panel performance. Combined with the liquid properties and the formulation, Crystic LS30PA is easier to use than most superior grade ISO-NPG’s. It can be backed up in one hour and 15 minutes, and the level of tack associated with ISO-NPG’s is quite low. In summary, the gelcoat demonstrated excellent weathering characteristics during extended exposure tests in Florida, with high gloss retention and low colour change. It met all the required criteria and received excellent feedback from various customer trials in leading boat-building areas. Liquid properties Due to the thixotropic nature of Crystic Crestacoat 5000PA, a layer of only 1 mm is needed to achieve all of its surfacefinish advantages (Table 3). This is a major advantage, as less is needed. Another unique result of its liquid properties is that it can easily be applied by brush or spray. Tab. 3: Liquid properties of Crystic Crestacoat 5000PA Liquid properties Property Appearance Viscosity at 25°C Specific gravity at 25°C Stability in the dark at 20°C Gel time at 25°C using 2% Butanox M50 Heat deflection temperature (1.80MPa) Unit Months Minutes °C 5000PA Light blue paste Thixotropic 0.6 3 25 62 Crystic Crestacoat 5000PA Scott Bader has developed Crystic Crestacoat 5000PA, a superior barrier coat that was designed to improve the surface appearance in applications where print-through of fibre glass (orange peel) is apparent. This “defect” is commonly noticed on areas where a dark gelcoat is used, on a complex mould or infused parts. Crystic Crestacoat 5000PA can be applied to reduce, if not eliminate, such “defects” (Figures 6 and 7). No38 January - February 2008 / JEC Composites Magazine

JEC COMPOSITES MAGAZINE - Issue #38 - January/February 2008

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #38 - January/February 2008