When a reaction injection molding (RIM) product needs an excellent color match, the third string color addition from the manufacturer will be the way to go. The third string is the time at which the color is added to the polyisocynate component and resin mixture, and is inserted at the mix head. To fully understand how a RIM manufacturer can color match a product to your specifications is a description of the RIM process itself.
Reaction Injection Molding Process
Injection molding has been around for a long time. The first machine was patented in the US in 1872 by John Wesley Hyatt and was used for Celluloid, an early development of plastic. The machine looked much more premature to the injection molding machines of today, but was the same basic principle of injecting the plastic through a heated cylinder into a mold. The resulting product cooled and the mold was opened and a new product was born. Reaction injection molding put a new spin on the process by combining two reactive materials – polyol and isocyanate. The components are fed from two separate chambers into a common mixing area and at that point, the mix head, is where the RIM color match is accomplished. The mixture is forced under low pressure into the mold cavity, is cooled and then released with this procedure taking within three to five minutes. This process was developed in Germany by Otto Bayer in 1960 when he was looking for a new type of nylon.
After Bayer discovered a way to produce polyurethanes, a whole new set of physical properties for urethanes was available. These products have superior physical properties in that they are extremely durable with high chemical and UV resistance. The variance of the products themselves is wide, with a very soft and pliable item possible and also a very hard end result – from flexible foam to a rigid elastomer. In addition, the capacity to offer an RIM color match makes producing devices such as wheel chocks, cable protectors and auto hoods and consoles an excellent choice. Thousands of formulations of RIM and many more color matches are possible. With the color added at the mix head, the casting crew of some manufacturers can switch colors with each molding pour, an advantage in time and money.
RIM Product Sizes and Weight
RIM manufacturers can develop a wide range of sizes, depending on the size of their production presses. Mold heights can range from 11 ½” to 36′ at a high quality producer, with 65″ in depth and 42″ wide to 84″ in depth and 60″ wide. This allows for huge RIM auto parts to be assembled, as well as monster wheel chocks used in mining and construction and three foot long cable protectors for these same industries as well as commercial and residential applications. In the case of the cable protectors, with much traffic passing over them, it’s appropriate to have a good reaction injection molding color match to improve the aesthetic quality of the organization ordering the product.