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Consider the Resin for Plastic Injection Mold Design

Plastic injection molding signifies the dreamy process through which plastic is converted into finished products that we use every day. This method is very common in today’s manufacturing industry. It produces everything from a small kitchen tool to car bumpers.

Resins have a vital role in this process. In this article, let’s look at resins, their properties, and all the necessary points that are to be considered.

Learn about the best resins for plastic injection molding. Explore various types and their applications in manufacturing

Role of Resins in Plastic Injection Mold Design

Resins serve the purpose of giving a finishing touch to the product. It works as a crucial unit in determining the product’s shape, durability, and characteristics. 

Along with it, resins have a strong role in determining and understanding the parameters of mold, such as its temperature, cooling rates, and flow properties during the whole injection molding process.

Essential Properties of Resins 

In order to choose the right resin for our mold design, it is important to understand the essential properties of resins. Let’s have a look at those properties.

Mechanical Properties

  • Strength
Tensile strengthIt tells you how much pull a resin can take before it breaks. Crucial for handles.
Compressive strengthSqueezing power a resin can handle. Important for weight-bearing furniture. 
Flexural strengthBending power a resin can take before it breaks. Crucial for beams and levers.
  • Stiffness and elasticity
Modulus of elasticityStiffness rating of resin. The higher the modulus, the lesser the bend.
Yield strengthA point where resins transform into temporary shape change to permanent shape change.

Thermal Properties

  • Glass transition temperature (Tg)

It’s a thermal property that determines your resin’s matter. If the temperature is below the Tg, your resin will be a hard solid, whereas if it’s above the Tg, it will be either liquid or rubbery.

ProcessingMelt temperature during injection molding should be above Tg for a smooth flow of resin.
Dimension stabilityCrucial for hot parts. 
  • Melting point (Tm)

Tm is the melting point at which resins transform from a solid to a liquid state. Melt temperature in injection molding is below tm. Therefore, it is important to know about the points for safety and avoiding thermal degradation. 

  • Thermal conductivity

Thermal conductivity is also known as heat transfer champ. Higher thermal conductivity is suitable for heat sinks, whereas lower thermal conductivity is suitable for insulators.

3) Chemical Properties

  • Chemical resistance

Chemical resistance refers to the resin’s ability to tolerate chemicals without getting destroyed. Different resins have different chemical resistance; some of these are:

Acids and basesResins resistant to acids and bases are ideal for containers and batteries
SolventsSolvent-proof resins should be chosen for exposed parts to cleaning fuels
Oils/GreasesChoose oil grease-resistant resin for machine parts.
Discover the essential chemical properties for effective injection molding processes. Learn how they impact material performance
  • Weatherproof

Resins should be chosen based on their weatherproof quality. Such resins can tolerate sun, rain, UV degradation, color fading, etc. These are very suitable for outdoor furniture, building materials, etc.

  • Biocompatibility

Biocompatibility is a crucial property for resins, which are used for the purpose of making medical devices and applications that have to come in contact with human tissue. They minimize toxicity in the human body. 

4) Electrical Properties

  • Dielectric constant

It measures the ability of the resin to store electrical energy. A high dielectric constant is used by capacitors to store electrical charge, whereas electrical insulators prefer a low dielectric constant.

  • Volume resistivity

Volume resistivity indicates resins’ resistance to the flow of electric current. High-volume resistivity is a good insulator for preventing electrical leakages. 

How to Select Resin?

We studied above about how crucial resins are in plastic mold design. Almost every parameter and the success of plastic finished products largely depends upon resins. Since it has a critical role, it is also important that the resin should be selected carefully. 

Following are a few points that should be considered before choosing resin for your injection mold design

Learn key factors in selecting the perfect resin for injection molding. Enhance product quality and efficiency now

1) Based on Functionality

  • Strength and flexibility: Resins are built differently based on their temperatures and varied degrees of strength and flexibility. 

For instance, if you are choosing resin for a car bumper, you require a strong and stiff resin-like nylon. On the other hand, you can use thermoplastic polyurethane for a phone cover. 

  • Heat resistance: Certain resins have a tolerance to extreme heat, such as Polyetheretherketone (PEEK), which is the best for manufacturing engine parts. 

At the same time, resins like Polystyrene are less heat resistant and are suitable for soft toys.

  • Chemical resistance: When chemicals come into contact with mold parts, there is a high chance that the chemicals will destroy or burn down the mold. Therefore, the resin must be chemical resistant. 

2) Based on Aesthetics

  • Color and finishing: Resins come in a variety of colors, which makes the molded parts much more appealing. Some resins give a natural color, whereas some resins can be pigmented in order to have specific colors. 

Another crucial factor is the surface finish, such as high gloss, matte finish, etc, which brightens up the mold design.

  • Dimension stability: Resins should be dimensionally stable. This is very important because the final shape and size of the mold design depend upon the resin’s dimension stability. Study the resin before choosing the one for your mold.

3) Cost Factor

  • Price of resin: After understanding the key factors of resin, you should also keep in mind your budget. 

For a high volume production, resins are usually affordable, whereas, for an application that requires unique properties, resins should be of the best quality, which is usually way too expensive.

  • Consider processing parameters: Some resins require processing for a long time. This would affect the cycle time and your overall production cost.

For instance, resin with a high melting point requires more time to cool down.

After you figure out the properties and factors based on which you have to buy resins, further you have to select the right one for you. Let’s dig deep into different types of resins that are available to us.

Types of Resins and their Applications

1) Epoxy Resin

Epoxy resins are strong and versatile. They have the properties of excellent adhesion and chemical resistance. They are used in adhesives and coatings.

2) Polyester Resin

Polyester resins are known for their affordability and ease of working. They are used in fiberglass laminates and reinforced plastics.

3) Acrylic Resin

Acrylic resins are known for their clarity, strength, and resistance to various climatic conditions. They are used extensively in clear plastics such as plexiglass.

4) Nylon Resin

Nylon resin is known well for its toughness and wear resistance. They are used in fibers, films, and plastic engineering.

5) Polyvinyl Chloride (PVC) Resin

Polyvinyl chloride resins are used in pipes, tubing, and flooring. They are known for their affordability and ease of working.

6) Polyurethane Resin

Polyurethane resins are known for their durability, flexibility, and resistance to harmful chemicals and water. They are used in sealants, adhesives, and foams.


Resins are the foundation of plastic injection molding. Choosing the right resin for your mold design is critical and necessary for the success and properties of your final product. 

Keep in mind the necessary factors for choosing the right and accurate resin for your mold design, such as aesthetics, cost, and functionality. Remember, the right resin is the pillar of your finished product and will make it more appealing and useful.

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