What is a thermoplastic compound?
A thermoplastic compound is a thermoplastic polymer that has been customized by blending in additives and/or colors so that the material (typically in pellet form) is ready to be processed—injection-molded, blow-molded, or extruded—and made into a final part for a specific use. Polypropylene (PP), for example, can be enhanced with reinforcing and strengthening additives to enable it to perform at a higher level. Polyvinyl chloride (PVC) polymers can be enhanced by adding raw materials that provide flexibility and ease of processing and that can provide features such as flame retardancy and UV stability. Nearly every type of thermoplastic is available as a specialized compound, and there are as many different types of compounds as there are different plastic products for different markets.
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What markets use polymer compounds?
Plastic parts for many markets can be made with fully formulated, ready-to-use compounds. The following are a few examples of markets and some of their common requirements.
Vehicles use plastic compounds designed precisely for interior or exterior parts. Color and style, impact resistance, amount of shrinkage, and resistance to warping, for example, are properties that are can be tailored by formulating a compound to meet specifications. Casy Study: An automotive customer had been using ThermoPlastic Vulcanisate (TPV) in a specific seat belt retention boot applications
Building and construction
Due to inherent weatherability, plastics have many advantages over traditional building materials, such as wood. Compounds for building and construction are used to make pipes, window profiles, fencing, siding, decking, and many other parts. Parts that will be outdoors or exposed to UV light can be made from compounds designed to resist these conditions.
Plastics are the material of choice for many consumer goods, including items that are approved for food-contact, such as food storage containers and baby bottles. Compounds can be designed to be free from raw materials that consumers may be concerned about, such as bisphenol A and certain restricted plasticizers. Thermoplastic Elastomer (TPE) compounds offer an alternative to PVC. TPEs are often used in consumer goods to add a “soft touch” surface. Different colors can be added to compounds to help differentiate a plastic part so that it has shelf-appeal.
Compounds for industrial uses have different requirements from those for consumer uses. Designed for tough environments, compounds are made to be oil and fluid resistant, heat shock resistant, flexible in extremely cold temperatures, and UV stabilized to resist weathering.
Healthcare today depends on plastics used to make safe and sterile surgical tools, medical devices, tubing, and bags to hold intravenous fluids essential for patients, to name just a few. To make parts for patients who are allergic to latex rubber, alternative materials such as TPE compounds can be used. For medical devices that must be sterilized before use, gamma-stable plastic compounds are designed to resist degradation caused by gamma or ebeam sterilization. Medical devices must comply with strict regulations, so manufacturers are careful about which compounds are used. Case Study: PVC Compound 'Animal By-product Free' solutions for Medical and Dental products
Wire & Cable
Compounds designed for voice and data communication, power, coaxial and a myriad of other electrical and electronic cables must comply with strict fire safety standards. Materials are formulated to provide protection from the environment while performing to a hierarchy of flame and smoke testing. Compounds for wire and cable have special additives to enhance flame retardancy, UV stabilizers to resist weathering, and are designed to work in combination to promote high-speed data exchange. “Low smoke halogen free” (LSHF) compounds are designed to be free of any halogenated materials and to produce low amounts of smoke in case of fire. Case Study: Plenum PVC compound replaces data cable insulation and jacket materials
What does a Plastic compounder do?
Companies that make polymers may sell different “grades” of a polymer that have a range of melt flow rates, contain some basic additives needed to keep the polymer from degrading during processing, and sometimes have other additives designed for specific uses. But there are many other types of additives needed to create desired properties—such as flame retardants, UV stabilizers, processing aids, or colorants, among many others. A specialty compounding company’s experts know just which additives can be combined to produce the desired properties in a cost-effective way. The polymer compounder also has special compounding equipment designed to precisely feed materials at the right ratios and to mix the materials well so that the compounds can function as they should. The compounder has the know-how to run this equipment optimally to obtain consistent, high quality compounds.
In some cases, a company making an extruded or molded part can add a color or additive masterbatch or concentrate to their machine along with the polymer. If the masterbatch can mix well enough in the short time it is in the processing equipment—depending on the processing equipment, the processing conditions, and the material types—a masterbatch could be a good option. However, if the color or additive in the masterbatch does not disperse well, problems such as streaks, gels, or inconsistent properties can result. A fully formulated compound has the advantage of optimal dispersion to avoid these problems.
What should I consider when choosing a plastic compounder?
There are many different plastic compound companies to choose from. A specialty compounder should be able to provide a plastic compound to meet the needs of your product, either off-the-shelf or one designed specifically for you. A compounder should have technical experts that can partner with you to bring you solutions and service support to deliver what you need. Here are some questions to ask when considering a compounder.
1. Does the compounder have expertise in the regulatory and environmental standards of your industry so that they understand your needs?
2. Does the compounder have local support in the region where you operate?
3. Does the compounder have the manufacturing tools and the expertise needed to produce consistent quality products?
4. How does the compounder test the quality of its compounds?
5. Is the compounder willing to develop a compound that meets your specifications? Are they responsive to your needs?
6. What is the compounder’s reputation for customer service?
Finding the right polymer compound that gives you the properties you need may be a challenge, but finding a compounder who can understand your needs makes the selection process easier.
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