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Polydur Laminating System

Working Procedure

Laminating

Prior to laminating, the Polydur gel coat SGP/L or KP25/OH25 surface should be "wet out" with the laminating mix, Polydur LG/EM25, to ensure bonding of the gel coat to the laminate. Polydur Emulsion EM25 and Polydur LG are mixed by first adding the powder to the liquid. It is suggested that a typical total mix should be: 1500gm (1000gm LG / 500gm / EM25), and for larger laminates: 3000gm (2000gm LG / 1000gm / EM25).

Mechanical mixing is recommended.


The result is a low viscosity mix, which will wet out fabrics like chopped strand mat or Neomat.

1500gm mix laminates 0.5m² using 300gm Neomat.


A typical laminate of two layers of 300gm Neomat should weigh approximately 8.0kg/m² maximum. Weights higher than this denote excess resin to glass ratio. 300gm Neomat is recommended for most applications and large areas can be covered quite quickly. It can be observed that Neomat has a looped side. When using two layers, it is suggested that the layers should be loop side to loop side. If three layers are used, the third layer should be loop side down in order to have a smooth back surface. Care should be taken as with any resin system not to "over wet" the glass. Any excess should be rolled out, using a lambs wool type roller which can be washed out in water after use. Neomat should be "wet out" off the job.

As Polydur adheres to itself at any time, there is not the usual constraint in timing when laminating the first layer. A uniform laminate thickness is important. Overlapping of laminates should be avoided because thick and thin sections may lead to distortion of the laminate, as with other resin systems. Whilst little or no exotherm occurs with the system using two layers, thick sections may cause local exotherm. Two layers of 300gm Neomat are considered suitable for most laminate requirements.

On laminates where added rigidity is required, local stiffening ribs can be used to achieve this. These can be produced by laminating one strip of Neomat over pre-cut foam strips, to form a box section, again avoiding excess resin. Particular attention must be paid to flanges because these aid subsequent de-moulding, add rigidity and stability to the laminate. Honeycomb foam sheet is ideal for this application.

The Polydur laminating system requires 20oC for optimum results. At this temperature, the laminate will be observed to cure within 2 to 3 hours by turning uniformly white and can be de-moulded at this stage. De-moulding is best achieved by using air pressure through holes or valves in the laminate to relieve the vacuum produced. To avoid damage to the model by drilling such holes, these are best provided during laminating. Suitable size pegs or valves can be placed on the model and laminated around, leaving valves in situ or pegs that can be removed. On de-moulding, it will be observed that the gel coat is no longer white. This requires a further 2 hours to cure, at which time the laminate can be considered cured and ready for use.

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