Elastomer Molding
The term elastomer, which comes from “elastic polymer,” refers to those polymers that are just that–elastic. In addition to being elastic, elastomers exhibit high levels of viscosity. Putting these two qualities together, it can also be said that elastomers have viscoelasticity. Often, the term elastomer is also used interchangeably with “rubber,” though they are not necessarily the same. Elastomers may be synthetically created or naturally derived. Whether, however, elastomers are synthetic or naturally derived, to convert them into usable products, manufacturers must engage in a process known as elastomer molding. Elastomer molding, or thermoplastic elastomer molding, yields high performance, top quality products, decreased waste and increased cycle times. Molded elastomer products also tend to be durable, corrosion resistant and water resistant. Industries that use them include, among others: sports and recreation, electrical engineering, transportation and automotive manufacturing, footwear and healthcare.
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Elastomer Molding Processes
Elastomer molding may be accomplished using one of a few processes, including compression molding and injection molding. In compression molding, manufacturers place a (usually) preheated piece of raw material in an open, heated mold cavity. Once the material is inside, the mold is closed from the top by a plug, top force or hydraulic arm, which then continues to apply pressure. The combination of pressure and heat cause the raw material to spread evenly, take the shape of the mold and cure. This method is used to create a great many elastomer products, from ultra-large basic shapes to rain boots. More commonly, elastomer molding is performed via the injection molding process, which is the fastest and most economical method. During this process, a collection of elastomers is heated, melted and injected into a preheated metal mold cavity. Inside the cavity, the material conforms to its shape, which represents the desired shape of the finished product, after which it is allowed to cool and harden. Other less frequently employed elastomer molding methods include extrusion and blow molding.
Types of Elastomers
There are two different types of elastomers that may undergo elastomer molding. They are thermoset elastomers and thermoplastic elastomers. Most elastomers are thermoset, which are plastic polymers that require vulcanization, or curing, to become strong and durable. In this case, the process of vulcanization is performed in one of two ways: either, one, through the introduction of high heat or radiation and high pressure, or, two, through the mixing of the polymer with a crosslinking agent/catalyst at an ambient temperature. The density of said crosslink depends on the pre-polymer mix or monomer that is used and the way in which the crosslinking is set up. Typical pre-polymer mixes and monomers that are used in this process include: epoxy, vinyl esters, acrylic resins, polyesters, furan resins, phenolic resins, amino resins and polyurethanes. Thermoset elastomers are soft, rubbery and springy, but, usually, once they are cured, they cannot be melted or reshaped. Products commonly formed fully or in part through thermoset elastomer molding include: fishing lures and jigs, figurines, printed circuit boards, mold runners, car parts, cements, adhesives, coatings, insulating foams, mattresses, flooring, synthetic fibers and more. The other group of elastomers that may be molded, thermoplastic elastomers, or TPE, contain materials that exhibit both elastomer and thermoplastic behaviors. Behaviors of the former include elasticity and viscosity, while behaviors of the latter include pliability and/or moldability above a certain temperature, and hardness once cooled.
Applications of TPE
TPEs are used to fabricate products like snowmobile tracks (which require the abrasion resistance and stiffness they supply), glass-run weatherstripping car profiles, dynamic weatherstripping car profiles, suspension bushings, the soles of shoes, catheters of varying hardnesses and a variety of medical devices. They may also be used for electrical wire insulation, for HVAC applications, as electrical cable jackets and adhesives.
Things to Consider When Choosing Elastomer Molding
The possibilities that elastomer molding holds for manufacturers and end-users are nearly endless. With both the properties of plastic and rubber, elastomer products are superior to the vast majority of their peers. They are strong, elastic, water resistant, corrosion resistant and recyclable. In addition, the processes used to create them create very little waste, consume little energy and are economical and easy to carry out. To find out what exactly elastomer molding services can do to increase the quality and lifespan of your applications, we recommend contacting one or more of the highly qualified manufacturers listed on our website.