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When mixing the GRP resin1, there are a lot of factors that must be considered. Always know roughly what the deck or temperature is, this can be achieved with either a thermometer or most phones now have one built in. the temperature reading is the indication as to how much catalyst will need to be added; once you have the reading get all the matting cut and in place as well as trims fitted, this will add to your ‘working time’ which is generally 10 mins on extreme temperatures to up to 2 hours cold conditions.
If this temperature is not taken into consideration and the wrong amount of catalyst added, then this will greatly impede your progress with the roofing insulation. The mixing buckets should be clean and dry, any old resin should be cleaned this will stop any contaminants leeching into the application and wall result in a imperfect installation as the resin/ matting is the main sealant process within the GRP installation process. A clean stirring stick will be required, and a separate mixing bucket placed to one side.
It is a lot safer to mix smaller amounts this will give you a feel and also curing process for the resin, (never use more than 4% or less than 1%) as the cure time will not be increased by using larger quantities and excess catalyst may damage the integrity of the laminate, commonly referred to as ‘gassing’, the forming of pinholes through the laminate. Below is a basic guide for resin/catalyst mix;
|Warm||<--- Catalyst Required --->||Cold|
|Quantity Resin (Litres)||1% Min||2%||3%||4% Max|
By using the above guide, we can see a typical pattern of the amount from the coldest day to the hottest. Always remember that the resin will cure faster in direct sunlight and keeping the resin ‘out of the sun’ will help the process. On a windy day use more catalyst as the wind will ‘strip out’ the styrene2, one of the components of the resin which will show the curing process.
Once you have all the equipment ready and trims fixed/matting into place, open the resin tin pour the amount required into the mixing bucket (a good way to remember that catalyst is added is to put the lid back on the resin tin once the catalyst has been applied). Stir the resin, use the catalyst dispenser to the right amount, add into the bucket and stir well.
As the curing process takes place a colour change to the resin will take place as it slowly starts to cure. The resin will thicken and start to lump until it quickly cures. If the resin cures the bucket will need to be cleaned and probably a new roller/brush used. Always keep your tools/buckets in a clean working order this will greatly aid you in the process to achieve a great looking finish.
If you would like to learn more about GRP Roofing our blog is full of information.