There are a few important considerations to make within any plastic injection molding process, and one of the key such elements is the resin that will be used. There are a wide range of plastic resins out there that have varying qualities depending on your final desired part, and these plastics can be heated, melted and otherwise used to form the parts you need.

At EnviroTech Custom Injection Molders, we’re happy to offer a wide range of polymer resins for use within our injection molding solutions, which cover a variety of industrial molding needs and related areas. What are some important factors to consider when selecting the ideal resin for your part and project needs? Here are several to keep in mind.

Intended Part Purpose

First and foremost, the specific purposes and uses of the final desired part will play a major role in dictating the ideal resin for your use. For example, some plastics are specifically designed to endure high temperatures and extended usage periods, which may be necessary depending on your final part’s place in an assembly or other application.

Furthermore, certain resins are more suited to selected applications than others – whether it is medical-compatibility with food or pharma applications, resistance to low temperatures or chemical exposure, or other requirements.

Here are some of the factors that should be evaluated in this area:

  • Potential stressors: What kind of wear and tear will the part see? What temperature extremes will it be exposed to?
  • Environmental conditions: What kind of atmospheres will the part be used in? Will it be exposed to solvents or other chemicals?
  • Manufacturing processes: What production steps will the part go through before use? Will it experience heat treatment or post-processing steps?
  • Material and Product Design: Will any elements of the final part need to be embedded within another material, such as a metal component within plastic or other materials used in bas relief on a surface?
  • Weight: Will the part need to be able to withstand its own weight, or the weight of other objects it will be in contact with?
  • Appearance: How important is the appearance of the finished part to the overall project? Some resins can produce a glossy finish, while others have a matte appearance.

All of these details will help to paint a more specific picture of the needs of the final part, and what type of resin would be best suited to meeting them.

Specific Aesthetic Needs

Within the final bullet point we went over above, there may be a few specific themes that come up depending on your product desires. Here are a few of these:

  • Part transparency or color: In many cases, a very specific color or translucency may be ideal for the part you are creating. This particular aesthetic need may require a specific resin that allows for either of these qualities, or even one that is colored or translucent on its own.
  • Part texture or finish: The surface finish of a part can be just as important as its color, and can add to or detract from the overall look. There are a range of textures that can be achieved with different resins, some of which may be more desirable for your needs than others.
  • Existing color match: As with color, the existing color of a part may be more important than its final texture. In some cases, it may be important to match an existing exterior finish on the part you are building with your resin choice.
  • Embossing considerations: Should you be considering elements of 3D bas relief in your final part, there are certain resins which will work better for this application than others.

Regulatory Requirements

Another vital area within the realm of plastic injection rosin selection is any regulatory requirements that may be specific to the type of part you are creating. Certain plastics – particularly those that are used for food or pharmaceutical purposes – may require certifications or other regulatory procedures in order to meet these needs.

You will want to make sure that your chosen resin is up to any needed specifications, and can be manufactured within a factory that also meets these regulatory guidelines. There are various regulatory requirements your part may need to meet, from FDA guidelines to LME standards, and you will want to make sure that your resin choice is appropriate for your needs.

In addition, there are many cases where the product in question needs to be safe for use by children. In these particular cases, there are a number of different resins that may need to be eliminated from the running because they contain known toxins. Similar themes go for part food safety.

Resin Morphology

Finally, we wanted to go over what’s known as the morphology of a plastic resin, or the arrangement of molecules in the resin. Generally speaking, there are two categories for resins here:

  • Amorphous: Amorphous resins are known to shrink less than other types when cooled, plus have ideal transparency. They’re perfect for tight-tolerance applications. On the flip side, they tend to be more brittle than their counterparts, plus have low chemical resistance.
  • Semi-crystalline: Semi-crystalline resins, on the other hand, are typically opaque in nature, plus have fantastic abrasion and chemical resistances. They are less brittle than amorphous options. However, they are known to come with higher shrinkage rates than amorphous resins, which can be an important consideration in some settings.

For more on how to choose the ideal plastic resin for your injection molded part, or to learn about any of our plastic injection molding services, speak to the staff at EnviroTech Custom Injection Molders today.