TL-0020 — Exotherm of PROCOR® Membranes Technical Letter (US Version)

PROCOR® is a two component, reactive system. One of the reactions that takes place during the cure process is exothermic (generates heat) and if the heat generated is not able to dissipate then rapid temperature rise could be seen. This process can also take place if PROCOR® Part A is contaminated with water. During the exotherm process temperatures as high as 290oF (130oC) could be reached and under these conditions the residual water from the PROCOR® Part B will vaporize creating pressure and resulting in a foamy consistency.

Exotherming is most likely to be seen if mixed PROCOR® is left in the pail after mixing. Once mixed, always install the entire contents of the pail as soon as possible. Do not seal containers once mixed with Part B or contaminated with water. Sealed containers may explode due to pressure from the reaction.

It is also possible that exotherming could occur on the substrate if PROCOR® is applied too thickly in a single application. The thickness at which the exotherm will occur depends upon PROCOR® grade and ambient temperature. The following guide summarizes when exotherm is likely to occur. If it is necessary to apply PROCOR® at thicknesses greater than those given below then the membrane should be applied in more than one layer, leaving a minimum of one hour between applications.

PROCOR® Grade Ambient Temperature    
  40°F (4°C) 70°F (21°C) 100°F (38°C)
PROCOR® 10 and 20 Greater than 3/4 in. (19 mm) Occurs at 3/4 in. (19 mm) Occurs at 1/2 in. (12.5 mm)
PROCOR® 75 (12.5mm) Greater than 1/2 in. (12.5 mm) Occurs at 1/2 in. (12.5 mm) Occurs at 1/4 in. (6.25 mm)

Areas of sponginess due to exotherming should be repaired by cutting away the affected area to solid, fully- adhered, correct thickness membrane. The exposed area should then be patched with PROCOR® to give a minimum overlap of 6 in. (150 mm) onto the existing procor. Where the surrounding area of PROCOR® is contaminated with dirt or is more than seven days old it should be pressure washed or lightly abraded with a wire brush, coarse sanding disc or similar to ensure good adhesion.

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This document is only current as of the last updated date stated below and is valid only for use in the United States. It is important that you always refer to the currently available information at the URL below to provide the most current product information at the time of use. Additional literature such as Contractor Manuals, Technical Bulletins, Detail Drawings and detailing recommendations and other relevant documents are also available on www.gcpat.com. Information found on other websites must not be relied upon, as they may not be up-to-date or applicable to the conditions in your location and we do not accept any responsibility for their content. If there are any conflicts or if you need more information, please contact GCP Customer Service.

Last Updated: 2020-01-16

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