Urethane Bumpers

Urethane Bumpers

Urethane bumpers are protective parts that function to absorb shock or to impede contact. Since they are formed from urethane, which is elastomer containing urethane carbamate links, this type of bumper has many advantages over conventional elastomers and plastic materials. Some examples of these benefits include high abrasion and impact resistance nose abatement properties, high load bearing capacities and a broad hardness range. However, hard urethanes (90A-95A) are best-suited for bumpers as they work best in impact applications. There are two main types of urethanes used to mold bumpers: ester-based urethanes and ether-based urethanes. Ester-based urethanes are characteristically softer, while ether-based urethanes are harder and have a tender, but brittle feel to them. In addition, ester urethanes offer excellent compression recovery, while ether urethanes have better UV resistance. Urethane bumpers are most often utilized in the automotive industry, but are also used in industries such as: electronics and appliance, for non-skid applications; industrial manufacturing, to guard, stop and align both machinery and work pieces; construction, for cabinet doors and additional building fixtures; and commercial, for products such as cutting boards and picture frames.

As a thermosetting elastomer, urethane is cured through heat and once it is cured, there is no way to alter the shape, unlike thermosoftening plastics that can be re-heated and re-shaped. In order to shape urethane, there are several different processes that could be used; however, molding is generally the process most often used. In order to begin the molding process, a mold must first be made in the desired shape. To create the mold, a master mold must be created through coating the pattern in a silicone-based liquid rubber. Once the liquid-coating hardens, the pattern is removed and a void, or empty cavity, is left behind that can be used to shape urethane into the bumper pattern. The most common molding process used to form urethane bumpers is reaction injection molding (RIM). To begin this process, urethane is mixed with a polyisocyanate component and then injected using a low-pressure pneumatic gun into fill holes that were drilled into the mold. Next, the mold is placed into a pressurized pot that serves to compress air bubbles that may have developed and become trapped during the injection process. Finally, after a certain amount of time has passed to allow for curing, the mold is removed from the pot and opened so that the newly formed urethane bumper can be removed.