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thermoplastic VS thermoset

Join Date: 2022-06-12

At one time, "thermoplastic" was the hard word for injection molding and parts manufacturing. However, the term has been replaced by one that sounds similar but means something different: thermosetting. Today, thermoset plastics and resins have become attractive alternatives to thermoplastics and other traditional components, such as metals and wood. While thermoplastics continue to be used on certain products, thermosets often offer additional advantages in terms of aesthetics and construction, as well as cost and labor. If you are considering purchasing a thermoformed plastic product or mold for a specific application, then this article may be helpful to you. This article will detail the two types of plastics and the differences between thermoplastics and thermosets to help you make an informed choice.


What are thermoplastics?

A thermoplastic is any plastic material that melts above a certain temperature and cures on cooling and can be remelted and remolded many times. This property also makes thermoplastics recyclable, which is why they are widely used in the toy, furniture, and apparel industries. Thermoplastics have varying temperature tolerances. Some can maintain their properties at temperatures up to 100 degrees Fahrenheit, while others can withstand temperatures up to 600 degrees Fahrenheit. Most thermoplastics also have good electrical and thermal insulation. They can also be electrically conductive if metal or carbon is added.

Common examples of thermoplastics include acrylic, polyester, polypropylene, polystyrene, nylon, and PTFE. The choice of material depends on the manufacturing project and the desired properties of the item being produced.

Some common places you can see thermoplastics include

  • Sports equipment
  • Toys
  • Automotive parts
  • Optical discs
  • Food storage containers
  • Eyeglass lenses
  • Grocery bags
  • Bulletproof undershirts

Thermoplastic Injection Molding

Thermoplastics are commonly used in injection molding because they produce flexible, accurate parts with excellent surface finishes. The process of thermoplastic injection molding begins with the creation of a mold, usually made of a metal such as steel or aluminum. The thermoplastic resin is then heated into molten form, which is then injected into the thermoplastic mold to cool and cure. After that, it is removed from the mold, and the entire thermoplastic molding process is complete. However, thermoplastic injection molding requires high temperatures and pressures to successfully manufacture parts. Therefore, it is not the most cost-effective solution.

What are thermosets?

A thermoset plastic is a material that remains permanently solid after it has been cured once. The polymers within the material cross-link during the curing process, creating an unbreakable, irreversible bond. It can also be described as a class of thermoplastics with enhanced physical and chemical properties. The dimensional stability of thermoset plastic products is greatly enhanced compared to traditional thermoplastics. Other benefits include:

  • Greater resistance to high temperatures than thermoplastics
  • Highly flexible designs
  • Thick-wall to thin-wall capability
  • Excellent aesthetics
  • High level of dimensional stability
  • High cost-effectiveness

Common examples of thermoset plastics and polymers include epoxy resins, melamine-formaldehyde, DAP (diallyl phthalate), urea-formaldehyde, polyurethane, and phenolic resins.

Thermoset Plastics Applications

  • Aerospace: thermoset molded interior components used in the nacelles of civil, commercial, and military aircraft.
  • Electrical: thermoset composites allow the manufacture of lightweight, durable housings for a variety of complex appliances
  • Automotive: thermoset molding provides lightweight materials for automotive manufacturing, and high-end automakers use carbon fiber composites to provide enhanced performance
  • Chemical: Corrosion-resistant thermoset plastic composites are important in chemical processing plants that handle low and high pH environments
  • Civil engineering: Roads, bridges, buildings, piles, and other structures use composite infrastructure applications to ensure durable performance at an economically viable cost
  • Construction: Thermoset composites form doors, window frames, wash basins, and a variety of other bathroom fixtures
  • Marine: Thermoset plastics are corrosion resistant, allowing them to be used for components exposed to salt water in commercial, recreational, and military boating applications

Thermoplastics vs. Thermosets

  • Thermoplastics can be remelted and recycled without changing their chemical properties. Unlike thermoplastics, thermosets cannot be successfully reheated and remolded.
  • Thermoplastics are typically stored in pellet form before the molding process begins. Thermoset plastics exist in liquid form at room temperature.
  • Thermoset plastics are typically stronger, have higher durability and dimensional stability, and are less prone to degradation. In addition, they do not warp or deform in extremely cold temperatures. This makes them ideal for any part of machinery used in extreme climates or environments with frequent temperature changes.
  • Thermoset plastics are also less hazardous to health than thermoplastics because potentially toxic fumes such as styrene are not released during the molding process.
  • Thermoset injection molding can be performed at a much lower cost because their molding process requires less heat and pressure. Another aspect of thermoset injection molding's low-cost advantage is also evident. Because of the excellent "flow" of thermoset plastics, you don't need to produce each small part individually and then assemble them as you would traditionally do with metal forging.
  • Parts made by thermoset molding can have different wall thicknesses in a single part that other materials and processes cannot.
  • Choosing thermosets does not mean sacrificing the high-quality finishes traditionally associated with the well-known thermoplastics. We can provide you with a low gloss or high gloss Class A finish directly from the mold. Painted thermosets such as polyurethane can also mimic fine textures, including stone, wood, and metal.

In summary, the greatest advantage of thermoset plastics is their heat and chemical resistance. Heat resistance is the main function of thermoset materials, while thermoplastic materials can only withstand some heat. mdc usually does compression molding of thermoplastics and compression molding of thermosets.

MDC experts have years of experience in thermoset materials and molding. This is not your everyday molding, and we are proud to be the kind of company that can provide this highly specialized service. At MDC, all of our molding processes are done in-house, ensuring complete control of the molding process from start to finish. We are happy to work with you to create the best part design and tooling for your plastic parts.

MDC operates in the automotive, industrial, bathroom, and electrical and electronic industries, specializing in providing them with high-quality thermoset molds and products. At MDC, we have the ability to produce walls as thin as 0.25 inches and as thick as 1.125 inches on a single part. Contact us today to learn more about how thermoset polymers can be the ideal choice for your next project!

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