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Polyurethane and Its Use in Injection Molding

October 27, 2017

When it comes to choosing a material for manufacturing parts, there is a veritable world of options. Steel, aluminum, wood, a vast array of plastics – not to mention more modern substances such as vinyl, polyester and sheet moulding compound (SMC). However, in recent years, one material has come to stand head and shoulders above the rest: polyurethane.

Polyurethane is an organic polymer which exists in both thermoplastic and thermoset varieties. Typically, polyurethane is formed using two components: di- or poly-isocyanate and polyol. It was first created in by Otto Bayer of IG Farben in 1937 in Leverkusen, Germany, where its initial use was as a coating for World War II military aircrafts.

Today, polyurethane sees use in a wide range of industries, from automobiles to heavy machinery to roller coasters to shopping carts. While polyurethane first gained popularity for its lightweight and flexible nature, it also possesses a variety of additional benefits which make it among the highest quality of manufacturing materials.

Here at Romeo RIM, we use polyurethane, polyurethane composites and polyurethane resin developed by our partner, Covestro LLC, in many of our reaction injection molding (RIM) and long fiber injection (LFI) production processes. We strongly believe that, whatever you may need manufactured, polyurethane just might be the solution for you.

Benefits of Polyurethane

Polyurethane first made waves due to its unprecedented light weight when compared with metal, wood, and even other plastics in polymers. Some of our LFI-molded polyurethane products are up to 60-80% lighter when compared with traditional metals such as steel and aluminum. Its light nature also makes polyurethane shapeable and flexible, perfect for use in the manufacture of foam products such as chairs and insulation panels as well as elastomeric wheels and tires.

However, polyurethane is more than light: it’s strong. Tough, durable, load bearing and impact resistant, it performs extremely well in crash tests even when compared with more “solid” materials such as metal. At Romeo RIM, all of our polyurethane-molded vehicle and machinery parts are impact tested according to established standards.

Our injection-molded polyurethane roofs, for example, are tested via dropping a 100lb ball from a height of 3 meters. The roofs experienced no headliner deflection greater than 9”, and in every test the ball failed to penetrate into the cab area.

Polyurethane also comes with a number of aesthetic advantages. It flows into the mold far better than any alternative material, allowing for the easy creation of parts with complex geometric shapes.

It can also be painted in the mold, which creates a high or low gloss Class A finish without necessitating an expensive, time-consuming post mold painting process. Painted polyurethane can easily mimic the finest and most detailed of textures, such as stone and wood grain. The in-mold painting process also creates a superior adhesion between the paint and the surface; the result is a long-lasting paint job that resists cracking, flaking and chipping even if exposed to extreme temperatures and elements.

In addition, polyurethane itself is extremely resistant to abrasion and wear. Wood rots, plastic warps, metal rusts, but polyurethane stands the test of time. It retains its shape at high and low temperatures – even continuing to function when approaching its melting point. This makes polyurethane ideal for machinery and other products that will be used in extreme climates.

If that wasn’t enough, polyurethane is also dielectric, making it a perfect choice for insulation. It resists water, oil, grease, chemicals, and radiation, which has led to its use in manufacturing spas, personal watercraft, and medical equipment such as MRI and CAT scan machines.

Finally, polyurethane is highly cost-, labor- and time-efficient. It produces no harmful styrene fumes, lowering the health risk for those who work with the material during the molding process. It also has a shorter in-mold curing time than any other product, allowing our customers to quickly and efficiently product large amounts of the products they need.

Polyurethane Injection Molding

At Romeo RIM, we use a reaction injection molding (RIM) process to create our high-quality polyurethane products. The two components, isocyanate and polyol, are stored in tanks which are pumped in and out of a closed aluminum mold in an endless circuit. Our choice of a closed mold improves the flow of the polyurethane, allowing for the creation of far more complex shapes than traditional processes such as compression molding or polyurethane casting.

The components are then mixed at a high velocity in an impinging mixer. Pressure is added to cause the chemical reactions which result in the creation of the polyurethane. The mold itself heats to a temperature of 325 while a small amount of pressure (approximately 100 psi) is applied, allowing the polyurethane to cure quickly. Cycle times for polyurethane products using reaction injection molding can be as low as one minute; even the largest and most complex of parts take only a few minutes to reach completion.

We also offer several alternative processes which allow the finished product to be even more strong and durable while retaining polyurethane’s low weight and flexibility. Reinforced reaction injection molding (RRIM) adds glass fibers, while structural reaction injection molding strengthens the polyurethane via the addition of a fiber mesh.

Romeo RIM’s signature technology, long fiber injection molding (LFI), adds long chopped glass fibers (traditionally between 0.5 inches and 4 inches in length) to the polyurethane resin to create products with unprecedented strength and toughness and a lower-than-ever cycle time.

Our polyurethane injection molding is the fastest, best, most cost-efficient solution for creating high-quality products in a wide variety of industries. Call us today to learn more about how polyurethane could be the solution for your next manufacturing project.

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