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Resin Bound Knowledge Base

Resin Bound Knowledge Base

Installation - Curing

Catalysts and cure time: StarScape ULTRA is a unique formulation which utilises the very latest technologies. This means that certain ‘common’ practices associated with older technologies do not apply. The StarScape ULTRA ‘A’ and ‘B’ components do not require pre-mixing and there is no need for a separate catalyst addition.

StarScape Ultra is available in two variations which both contain a combination of catalysts pre-blended into the resin. Whilst this may appear to offer less flexibility than systems which require a separate catalyst addition, it actually removes any uncertainty regarding the quantities of catalyst required and prevents the variable curing process from changing the appearance or reducing the performance of the completed installation.

StarScape ULTRA is supplied in two variations:

StarScape ULTRA application temperatures
StarScape ULTRA+ curing temperatures

It is far from simple to formulate a stable system that achieves the desired cure profile, meets high performance standards and retains an acceptable shelf-life. As such, many systems are limited to the levels and type of catalyst they can use in their formulations. Systems that state a level of performance also state that any addition of catalyst is outside of any such standards or approvals.

Practically speaking, the use of too much catalyst will result in the gel time or ‘front end cure time’ being much shorter. This reduces the time in which the resin remains workable or can be trowelled level. Too little catalyst results in a much longer cure time which prevents the surface becoming trafficable and leaves the resin open to undesired side-effects as both the gel time and final cure are delayed.

On a molecular level the polyurethane and polyurea reaction with catalysts are complicated mechanisms with both the resin and isocyanate components forming complexes with the metal content of the catalyst. The level of catalyst and the type of metals it contains, influences how the reaction proceeds and which reaction is preferential, be it resin and isocyanate or the isocyanate and water reaction. The type, order and speed of cure all effect the performance of the final system and altering the cure profile can allow undesirable side reactions to occur such as the reaction of isocyanate (Part B) with water to form a urea rather than reacting with the resin (Part A) to form a urethane. Although a small amount of urea formation is desirable it shouldn’t be to the detriment of the main polyurethane reaction.

Using different levels of catalyst to suit the ambient temperature will initially seem to give the desired results however by doing this the systems cure profile is altered. The 'back-end' urea reaction which increases the overall physical properties is reduced or removed altogether. This can cause a significant reduction in performance. The area in the centre of the image is two year old StarScape ULTRA, pre-catalysed with a carefully calculated level of catalyst.

Resin bound colour change due to catalyst levels

2 Years Old - Same aggregate laid on the same day

StarScape Ultra has been formulated to provide the correct balance between the front end and final cure to optimise both application time and the time before the surface can be trafficked. The two systems ensure all temperature fluctuations in the UK are catered for. The rate at which any resin bound surface cures is affected by several factors with higher temperatures increasing the rate of cure and lower temperatures reducing the rate of cure. All of the following factors can greatly change the rate of cure when combined:

Ambient Temperature

The ideal temperature for the installation of a StarScape ULTRA surface is between 10⁰C and 20⁰C. At temperatures lower than 3⁰C the cure time is reduced to a point that moisture or frost can damage the surface whilst temperatures greater than 30⁰C can reduce the trowelling times to unmanageable levels.

Surface Temperature

In direct sunlight, the temperature of a dark coloured base (such as asphalt) can be over three times greater than the ambient temperature. In such cases the material trowelling times can be reduced to unmanageable levels.

Aggregate & Resin

Both the resin and the aggregate should be stored in a cool, dry and sheltered location. If the bags of aggregate are allowed to heat up in sunlight and are then cooled over-night, condensation can form within the packaging. This can be enough moisture to both speed up the cure time of a mix and reduce its overall matrix strength when fully cured. Under no circumstances should aggregate be used if condensation is present within the packaging.

Mixed Resin

As soon as the resin components begin to mix together the chemical reactions which cure the material has started. The reaction cannot be slowed and it is imperative that the mixed material is trowel applied as soon as possible. As the curing reaction continues the mixed material will become tackier to a point that it is no longer possible to trowel it to a smooth finish.

Temperature: The average daily temperature in the UK is 10.5⁰C and ideal for the installation of a StarScape ULTRA surface. The following table shows the average UK monthly temperatures and their suitability for installing a resin bound surface:

Average UK temperatures

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In the height of summer, the average daily temperature in the UK is 17⁰C. It should be noted that this is the average temperature and on certain days it is not uncommon to expect temperatures that exceed 30⁰C. The following table represents the key curing stages of StarScape ULTRA at 17⁰C:

Resin bound curing stages

The curing process of StarScape ULTRA happens in two stages. The first stage (front-end cure) is where the material achieves 90% of its full strength in a 24-hour period. The second stage (back-end cure) is where the material slowly continues to grow in strength over a period of days.