Specialized Solutions for Polyurethane Injection Molding
Injection molding is a common process for many polyurethane products. Examples of the various markets that use polyurethane injection molding are: integral skin, rigid, back foam, shoe soles, office furniture and automotive interiors from arm rests to sound insulation. In many applications the mold release agent is applied to the mold, and then a paint coating is applied over the mold release agent. The mold will then be closed and the injection will take place. The final product will be removed fully painted.
A closed mold usually contains some form of channels after the mixer gate† designed to improve the laminar flow of injected polyurethane at the entrance to the mold. The closed molding process offers advantages in the shape and complexity of the molded product. Chem-Trend’s involvement with many different polyurethane applications, as well as with injection molding systems in other industries, provides it with release agent development expertise unmatched within the polyurethane injection molding industry.
Injection molding differs from the open pour in contact angle and mixing motion, which leads to different stresses on the mold release agents. Injection molding is very common in the application of pre-painted polyurethane parts, which again creates more variables to the production equation, such as utilizing different paint suppliers while achieving the correct gloss and feel.
RIM stands for Reaction Injection Molding and is the process of injecting material by using a high-pressure impingement-mixed stream into a mold or cavity†. Other acronyms related to RIM are RRIM and SRIM. (RRIM – Reinforced Reaction Injection Molding, has reinforcement particles suspended in the chemical stream. SRIM – Structural Reaction Injection Molding, uses continuous fiber structures that will be pre-located in the injection mold.)
Release agents used in RIM processes need to be able to resist movement and disruption during injection and still be mobile enough to produce a slippery surface, once the PU has been cured. Additionally, the material composition of the polyurethanes can interact differently with the mold release agents, creating additional challenges. Other considerations come into play with respect to the amount of material that is left behind by the mold release agent. A low amount of residual material left in the mold is highly desirable to reduce the cleaning frequency of the mold. Mold release application is very critical to meet the needs of the customer’s application. Often the application window determines the balance between good release properties and excessive material building up in the mold.
At Chem-Trend we understand that your parts need to be perfect the first time out of the mold. Reaction injection molding (RIM) presents a set of unique challenges that require a mold release agent with excellent release properties, optimal surface finish – whether high or low gloss – no surface defects and low build-up on the mold. All of our products have excellent release performance that reduces sticking in the injection ports and vent† holes of the molds. Some of our mold release agents are specifically designed to be easily washed off, which makes them an excellent choice to work with post-molding applications such as painting or gluing. With over 50 years of experience in developing and manufacturing mold release agents and related products for the polyurethane industry, Chem-Trend knows how to develop the right release products for your application. At Chem-Trend we can custom formulate mold release agents, mold cleaners, mold preparation pastes, anti-squeak products and flushing solvents to add productivity, quality and overall value to your bottom line. Our products work together as a total solution to improve your performance.