Manufacturing: Surface Finishing

Polyurethane Coatings

Polyurethane coatings are protecting many different structures today, such as storage tanks, oil and gas pipeline, water and wastewater, bridges, ships, and other facilities. The products have been effective because of their outstanding life expectancy and performance, resistance to aggressively corrosive environments, high abrasion resistance, fast application, low and cold temperature curing capability, strong adhesion, unlimited film build, and compliance with the most rigorous regulations on volatile organic compound (VOC) emissions.

Properties

The properties of 100% solids polyurethanes vary from very soft, rubbery elastomers (like running shoe soles) to hard, ceramic like systems - a good chemist can formulate the 100% solids polyurethanes to do almost anything. The chemical bonds in the more rigid systems are highly cross-linked to each other to create hard, dense systems that have very good chemical and moisture resistance. The rigid systems usually have excellent adhesion and are the best choice for the corrosion protection of metals. On the other hard, the elastomers have a more linear structure with much less cross linking that allows them to be very stretchy and elastic. These systems normally have great impact strength and flexibility, but relatively poor adhesion and chemical resistance. Elastomers are better suited to protecting substrates that tend to move and flex like concrete but do work as well on metallic substrates. The chemical and corrosion resistance of the elastomers can be improved if the systems are applied relatively thick.

Advantages

100% solids polyurethane coatings offer very unique handling, performance and environmental advantages. To the end users, this means a greater assurance of achieving the desired result on time and on budget. To the applicator, it means high throughput and fewer callbacks. Imagine, for example, coatings that:

• are 100% solids, having zero or near zero VOC's
• set at virtually any temperature - winter and summer
• are non flammable, solvent free and as safe as house paint
• are self-priming
• can be applied in a single multi-pass coat to any dry film thickness
• set in minutes
• can be put into service within hours
• are easily touched up if damaged
• are non-dangerous goods for transportation
• require no post curing, ever.

Accompanying these handling advantages are a number of important performance advantages.

• superior adhesion without using any primer
• resistance to chemical attack
• resistance to gouging and abrasion
• flexibility and resilience
• inertness, freedom from embrittlement
• impermeable
• resistance to disbondment forces
• a number of national and international approvals (UL, NSF, British Gas, etc.)
• a totally monolithic, seamless polymer sheet virtually fused to the substrate.

Application

100% solids polyurethane technology is available in a variety of setting times to allow application techniques including "brush and roller", "hand spray", "automatic line travel" and "casting". Typically, the setting (or cured-to-touch) time for these polyurethane systems ranges from less than one minute to several hours.