Tutorial Menu: Polyurethane Resin

Article compiled by Seunta LLC

A resin sculpture is a statue or other piece of three-dimensional art that has been cast using fiberglass resin. Resin is a fairly lightweight, durable material that can be painted and glazed to look like stone, porcelain, bronze or marble. It is used to manufacture a wide variety of products.

Polyurethane resin is our choice material because it is generally easy to manipulate and form into molds. In a liquid form resin can be poured into molds. When used for this purpose, the material is highly impressionable, which means that the slightest detail, such as a small crack, can be seen in the finished product. It is also easily manipulated via sanding and shaping once the resin has set, and it can be painted to effectively create a realistic tone to any piece.

Polyurethane resins are an industrial product, most often used in the manufacture of inks, the formation of molds, in plastics and bonding materials. These resins are malleable, their properties of hardness and elasticity can be altered and, once set into a final form, do not change back to their original form.

Polyurethane resins have a wide variety of uses, both in consumer goods and for industrial purposes. In consumer goods, these resins are found in inks, paints, modeling compounds, bonding compounds, varnishes and other protective coatings. They can be produced in varying forms, including hard, glossy, solvent-resistant coatings or abrasion- and solvent-resistant rubbers, fibers and flexible-to-rigid foams. The wide versatility of polyurethane resin can be seen in the fact that current uses of this resin include flooring, surfboard coatings, paper weights, jewelry and circuit boards. The polyurethane resin UX-5100A is used as the film-forming component of paints used to coat the external primed steel surface of car bodies.

Polyurethane resin is divided into two types, based on the properties of their liquid components: isocyanates and polyols. In North America, the isocyanate type is referred to as "A-side" or "iso." The blend of polyols, which includes hydroxyls and other additives is referred to as "B-side" or "poly." The terms "A-side" and B-side" are reversed in European countries. Most polyurethane resins are sold in kits with pairs of A-side and B-side because the two types must be mixed to produce the desired resin compound. Once mixed, they are fast setting. Choices of casting kits range from rigid to flexible, of varying degrees of hardness and opacity.

Polyurethane chemistry is versatile, allowing the engineering of specifically desired products. Polyurethane resins are noted for their durability and resistance to oil or grease. Besides being excellent at resisting abrasion and not easily torn, these resins can bond composite structures together, forming adhesive bonds that are impact-resistant, solidify rapidly and can adhere to any number of surfaces, including concrete.

Polyurethane resins are susceptible to yellowing when exposed to fluorescent lighting and, in some cases, can be adversely affected by direct sunlight. Unpainted resin castings will yellow over time - more quickly when exposed to ultra-violet light. Resin sculptures are hardy but not indestructible. Cold, freezing conditions can cause resin to crack because the material contracts, then it expands when the temperature rises.