Injection molding is a technique to manufacture flexible, strong molded parts at high volume from solid silicone rubber. Silicone rubber is an extremely useful industrial lubricant and thermosetting thermoplastic. It has excellent mechanical properties, including creep resistance, dielectric strength, flexibility, and thermal conductivity. The best silicone oils possess these characteristics and are used to create the various parts that make up a variety of appliances. This article briefly covers the techniques that are commonly used in injection molding of silicone rubber.
Most people are familiar with the process of pouring liquid silicone rubber into a mold and then molding the part directly out of the mold. That's just the simplest form of how molding silicone rubber works. While there are a variety of ways to create molded parts this way, they are typically done in large commercial equipment. However, you can also create molded parts this way with a variety of tools available to the home craft enthusiast.
You have a few choices for molding silicone rubber when creating items with liquid silicone overmolding. The most common and inexpensive way to create molded items out of the liquid material is to use silicone overmolding thermoplastics. You can choose between two different types of overmolded silicone overmold: polyethylene (PE) and ethylene (EO). Each of these varieties produces a unique appearance, which you will also notice depending on what you are making.
Another type of molding silicone rubber that you might encounter in your silicone rubber molding projects is known as thermoplastics. Thermoplastics are a unique cross between silicone oils and polyurethane (PVC). Because both materials exhibit the property of being rigid, thermoplastics allow for greater degrees of flexion and expansion than their silicone counterpart does. This means that you can mold products using this cross between materials, including rubber gloves, bumpers, and wrist straps among other items. You'll also find that thermoplastics exhibit some unique properties of having a temperature range similar to the temperature range of silicone oils.
A final type of molding silicone rubber that you may encounter in your silicone rubber molding projects is called compression molding. Compression molding is an extremely versatile process that allows you to create a wide range of shapes, such as beads, balls, and light blocks among other objects. In order to complete the molding process, you must allow the silicone material to sit for an extended period of time, typically over one to two weeks. During this time, the temperature of the silicone material will continue to increase and reach its equilibrium point. Once the equilibrium has been achieved, the item will be ready for production.
One of the most popular forms of liquid silicone rubber for molding is called transfer molding. Transfer molding is when a rubber product is melted down and moved from one mood to another. For instance, if you were working on a light ball or bead shape, you would first melt down the rubber molding until it had completely formed into the shape of the object. Then you would then apply pressure onto the formed product until it complied with the molding process and then remove it once the pressure was removed. There are a few differences between transfer molding and compression molding, but they are both very successful at creating unique shaped objects.
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