RESINS, A SYSTEMIC VISION
There is much talk about mortar, self-leveling, spatulate, multilayer coatings and paints, but we must remember that these denominations refer to the executive system, the relationship between resin and loads and not the resin that compose them. It is true that until recently coating was always termed “epoxy coating” in reference to the epoxy resin, base of almost all coatings available in the market. With the increase of commodities, the need for new solutions to epoxy problems and limitations, resins with new characteristics were presented to the national market. In this article, we will evaluate the resins, advantages and disadvantages and their best applications.
Liquid Epoxy Resin = READ
It has been for many years and is still the most widely used resin in the formulation of RADs. The main reasons are low cost, high versatility, easy handling, high gloss, good chemical resistance (mainly to abrasion), low toxicity and, in 100% solids formulations, have low odor or low VOC. It is a resin that can be used to formulate any type of system, from painting to mortar, it can have a fast or slow cure, depending on the curing agent used (hardener). Among its limitations is the fact that epoxy systems are highly impermeable, which makes these systems susceptible to uplifting humidities. However, this same characteristic is an advantage when it is desired environments with high contamination control, as, for example, in the pharmaceutical industry, surgical centers, etc. Another restriction for their use are systems exposed to thermal shocks, temperatures below 5 ° C or above 80 ° C. Epoxy resins exposed to ultra violet (UV) rays yellow and calcine, so they should never be used in external areas. The virtues of the epoxy resin accredit it as excellent for formulating internal systems with high traffic, where it is desired brightness, simple maintenance, low cost and easy handling.
Cement Urethane Resin
This combination of Polyol (compound based on vegetable oils), MDI isocyanate and cement has been the great novelty in recent years as the basis for high performance coatings. Cement Urethane systems have been filling a gap in which epoxy systems were not very efficient and high thickness ceramics are expensive and limit cargo handling. The great advantage of composite systems with cementitious urethane is precisely the disadvantage of epoxy systems. They support large thermal cycles (steam floor washing), have sufficient permeability to withstand rising humidity, can be applied to surfaces with humidity up to 12% and withstand temperatures from -45 ° C to 120 ° C. With an anti-slip surface, it is currently the ideal system for the food industry, slaughtering, refrigeration and drinks. As disadvantages have their rustic aesthetics, the same sensitivity as epoxy resins have when exposed to UV rays, high resin reactivity, color limitation and low storage time.
Methyl Methacrylate or MMA Resins
MMA resins are rarely used in Brazil. In temperate countries they are used in food plants, competing with Cement Urethane resins. Its main feature is its high reactivity, reacting within minutes and is the only resin that reacts at temperatures below freezing. It is commonly used in emergency repairs in cold rooms. It is usually more expensive and requires the purchase of various types of resin to formulate a system, unlike epoxy systems that require only one resin. As a disadvantage is that it exudes a strong odor during the curing process, at temperatures above 25 ° C it is extremely difficult to handle, has a limited range of colors, yellow when exposed to the sun, can not be used on damp surfaces and Do not allow the dissipation of rising humidity.
Polyurethane resins are probably the most versatile and with the greatest number of applications in our daily lives. With Polyurethane it is made from soles of shoes until thermal insulation of spaceships. In the world of high-performance coatings their main application are the varnishes and finishing paints. Because of its high resistance to UV rays, chemical and abrasion (aliphatic PU), the coating companies mainly use it as a top coat = Top Coat. High-solids aromatic PUs can also be used in the composition of systems, but are usually used in commercial and residential systems because they are softer and less resistant to impact, etc.
Polyureas and other hybrid resins
Polyureas are 100% polyurethane blended resins. Its main feature is the application process. Unlike traditional polyurethanes, they require special resin preheating equipment and nozzle mixers, since the application time is only a few seconds. Its application is mainly in containment tanks and waterproofing to have a characteristic of good elongation and superior resistance to acids and bases.