Everywhere you look, you see flat surfaces. Some of those surfaces are floors. Some of those floors have functional problems. Some of the problems have been plaguing you for some time. You want answers, you have questions.
Those are the major premises behind this question and answer session. Imagine yourself, if you will, sitting in a technical session about flooring at a conference. There is a panel of experts seated at the table in front of the room. Imagine them fielding questions from the audience.
We contacted three well known and respected suppliers to the flooring industry for the technical session. Let me introduce you to our panel for this 1997 edition of the flooring Q&A. They are Mark Moran, Director of Rock-Tred, Gary Hall, Eastern Regional Manager of Sauereisen Specialty Cements, Hank A. Bruflodt, Director of Technical Services of Floor Seal Technology, Inc., and Charlie Bloss, Southeast Regional Manager of Floor Seal Technology, Inc. So, let's get on with the purpose of the session.
Q1: We frequently hear the term 100% solids used to describe industrial flooring products. What percentage of industrial products are actually installed as 100% solids? What are these products?
Hall: Probably less than half are 100% solids. Solvents and reactive diluents improve working characteristics, flowability, working time, and reduces cost. However, the 100% solids materials are less permeable, more environmentally friendly, and meet EPA VOC limits. Many times contractors add diluents so systems designed to be 100% solids end up being something else.
Bruflodt/Bloss: With the VOC requirements that are in place, the percentage of this material that is installed is increasing. The term '100% solids' refers to the exclusion of volatile organics from a product. The 100% solids material do not release VOCs into the atmosphere. The current laws dictate that each State formulate their own VOC requirements. However, this could, at some time, become a national requirement that impacts the entire flooring industry.
Q2: When an industrial flooring product is said to cure, what does that really mean? When does the curing process actually stop or reach its completely cured state?
Bruflodt/Bloss: A product is cured when the chemical reaction is complete. This is not to be confused with drying which is generally much quicker. A polymer flooring material may dry in a matter of hours and not completely cure for weeks.
Hall: Cure refers to the chemical reaction that takes place when the components are mixed. The reaction rate determines working time and cure time. There are two stages to curing. The first—called hardening—involves reactions between resin and hardener. Once the mix is no longer fluid or plastic, cross-linking becomes the dominant reaction. Novolac resins harden and cure at exponentially faster rates than bisphenol formulations. Complete curing may require a month or longer. In general, cure rates are directly proportional to temperatures. The cure rates for different formulations for low or high temperatures vary accordingly.
Q3: Why do different products have different cure times?
Hall: Reaction rates determine cure times. More reactive molecules speed up the reaction rate and reduce the cure time. Solvents and diluents slow the reaction rate. Even though there are thousands of combinations of resins, hardeners, solvents, and diluents, correct stoichiometric ratios are absolutely critical in achieving the desired results.
Bruflodt/Bloss: Products have different cure times because of different chemical compositions. Product literature from any manufacturer specifies the drying and curing times and those parameters must be budgeted into the course of installation.
Q4: Do all products cure by the same chemical process?
Bruflodt/Bloss: No. There are several different curing processes: exothermic, endothermic, atmospheric reaction, and curing by evaporation, to name a few. Again, it is important to understand the necessary curing process the product manufacturer requires and build that time into the total project installation time.
Hall: No. Some reactions are simple addition reactions, others are condensation reactions, some are influenced by ultraviolet light. Even within a generic class of resin there are different reaction routes possible.
Q5: Why are different products able to cure in cold temperatures and others cannot?
Moran: Certain products cure in cold because they are inherently more reactive than products that require heat to cure them. Heat is a form of energy and some products do not cure at low temperatures because there is insufficient energy available to complete the reaction. In general, a given product cures less rapidly at lower temperatures.
Hall: The choice of hardener and resin determines whether a material cures at low temperatures. Highly reactive resins and hardeners cure at lower temperatures. Faster curing systems have lower chemical resistance. The problem is one of balancing cure temperature with pot life, chemical resistance, viscosity, and workability.
Bruflodt/Bloss: The nature of the polymer used dictates how the product is to be properly cured. Therefore, polymer coating product manufacturers have various chemistries for particular climatic conditions.
Q6: Why do certain coatings, when used outdoors, eventually chalk and turn brittle? Are there any products that can be used outdoors that will not chalk and turn brittle?
Hall: Ultraviolet light in sunlight degrades the resin and breaks the chemical bonds. This leaves a chalky film of fillers and exposed pigments on the surface. The film weathers and exposes more resin to degradation. Acrylics and aliphatic urethanes have the best UV resistance but may not be suitable for the expected chemical service. Adding UV blockers and inhibitors improves UV resistance.