Knowledge Base

Cure times

The time taken for StarFix adhesives, coatings and sealers to cure

Every product in the StarFix range has been formulated to provide the ideal balance between working time and rapid strength development, helping installers work efficiently without compromising long-term performance. Depending on the product, cure characteristics such as liquid working time, skin formation, tack-free time, through-cure and full cure have been carefully engineered to suit their intended application.

The guide below provides typical cure times for each StarFix product under standard laboratory conditions of 20°C and 40–60% relative humidity. These values should be used as a general reference, as actual cure rates will vary depending on substrate temperature, ambient temperature, humidity, film thickness and ventilation.

Our technical team is always available to provide advice where installation conditions fall outside normal operating environments, ensuring you achieve the optimum performance from every StarFix product.

StarFix adhesives - Temperature & Humidity

StarFix pedestal adhesives are single-component, moisture-curing polyurethane adhesives. Their cure is dependent upon the availability of moisture and is therefore influenced by a combination of ambient temperature, substrate temperature, relative humidity, ventilation and the depth of adhesive applied.

Under normal conditions, increasing temperature and available moisture will generally accelerate the polyurethane curing reaction. However, extreme or rapidly changing site conditions can produce less predictable results, particularly where high substrate temperatures are combined with low available moisture or where the adhesive is applied in a relatively deep section.

Recommended Conditions

For consistent application and curing, StarFix pedestal adhesives should ideally be applied at ambient and substrate temperatures between 5°C and 25°C, with adequate ventilation and a relative humidity of approximately 40–70%.

Conditions outside this range do not mean that the adhesive will fail to cure, but additional time may be required and cure development should be confirmed before testing or placing the installation into service.

High Temperatures

At elevated ambient or substrate temperatures, the viscosity of the adhesive will reduce and surface reaction can occur more rapidly.

In some circumstances this can result in the adhesive becoming surface dry or developing a skin before the material beneath has achieved full through-cure. The appearance of a dry or firm surface should therefore not be taken as confirmation that the complete adhesive layer has reached its final mechanical properties.

High substrate temperatures can also significantly affect the local conditions immediately surrounding the adhesive. As air temperature increases, its relative humidity can fall unless additional moisture is present, potentially reducing the moisture available to sustain the through-cure reaction.

For this reason, particular care should be taken where substrate or ambient temperatures approach or exceed 30°C.

Low Temperatures

Low temperatures generally slow the polyurethane curing reaction and increase adhesive viscosity.

Where installations are undertaken towards the lower end of the recommended application-temperature range, installers should expect cure and strength development to take longer than under standard laboratory conditions.

Cold substrates should also be checked for condensation before adhesive application.

Humidity & Moisture

Moisture is required for StarFix pedestal adhesives to cure.

Very dry conditions can therefore significantly extend cure time, particularly where the adhesive is applied between relatively impermeable materials or in a deep layer.

Conversely, high humidity can promote rapid surface reaction. The relationship between temperature and humidity is therefore more important than considering either measurement in isolation.

Testing After Installation

A pedestal adhesive becoming skin-dry or tack-free does not necessarily mean that it has achieved full cure or final mechanical strength.

Where pedestal installations are to be subjected to a T42 swing-bag test, sufficient time should always be allowed for the adhesive to develop the required mechanical properties. Under normal installation conditions, testing should not be undertaken prematurely. Where conditions have been unusually cold, hot, dry or humid, additional curing time should be allowed.

If there is any doubt regarding cure, the adhesive should be physically examined before testing.

Assisting Cure in Difficult Conditions

Where a moisture-curing StarFix pedestal adhesive has remained insufficiently cured because of unusually dry or adverse environmental conditions, the availability of additional moisture can assist the curing reaction.

Where appropriate, a fine mist of clean water may be applied to the exposed adhesive surface. The adhesive should not be flooded or saturated.

This measure should only be used where the adhesive has already been installed and insufficient available moisture is considered to be contributing to delayed cure.

Important

The cure times shown on this page are typical values rather than guaranteed site cure times.

Actual curing will depend upon the product, quantity applied, adhesive depth, temperature, relative humidity, substrate conditions and ventilation.

Where installation conditions fall significantly outside the recommended range, please contact Star Uretech for technical advice before testing or placing the installation into service.