Injection molding is a manufacturing process involving injecting molten plastic into a mold to create various products. Different injection molding materials include Peek, Carbon Peek, Nylon 4,6, and Nylon 6,6. Continue reading for more.
Injection molding is one of the most optimized and fastest methods of producing an incredibly high volume of identical and intricate plastic components at a go. This production process is the most common plastic manufacturing method used in almost all consumer plastic products while reducing the cost per unit.
This makes it easy to create custom plastic components. However, it becomes easier to determine whether or not a particular plastic injection molding will be suitable for your application if you understand the varying surface finishes and materials available.
This article focuses on the different injection molding materials, plastic types, and applications. These materials have numerous melting points according to the requirements of different applications.
The Different Plastic Types and Applications
Here are the different plastic types you should know:
PEEK
PEEK (polyether ether ketone) is a high-performance thermoplastic with excellent or highly impressive ductility and strength. It is an FDA-compliant material for food contact and can easily be sterilized for medical purposes or applications.
PEEK is an inert substance, making it one of the few materials that can be used in several applications, especially those requiring chemical resistance. For example, the oil and gas, as well as medical industries, make use of PEEK for plastic components.
This is why PEEK is often used for making the following components:
- Gears
- Bearings
- Manifolds
- Medical implants
- Surgical instrumentation
PEEK has several benefits that make it ideal for use. Some of these benefits include:
- Resistance to chemical
- Food safe
- High ductility
- Excellent strength and stiffness
The drying temperature of PEEK components is 150 degrees Celsius /3 hours or 120 degrees Celsius/ 5 hours.
Carbon PEEK
Carbon PEEK is a composite material with a PEEK matrix for components with extremely high structural characteristics. In other words, this material is reinforced with carbon fiber, and its extraordinary characteristics cover chemical, mechanical, and thermal resistance.
Reinforcing this composite material with carbon fiber further enhances its resistance from a mechanical perspective. This makes it possible for users to adopt its use during metal replacement processes in extreme industrial sectors.
Some characteristics of Carbon PEEK include:
- Mechanical resistance (boosts its structural functionality by up to 280 degrees Celsius)
- Chemical resistance, thanks to the PEEK polymer matrix makes printed parts resistant to most acids, organic solvents, and bases at high temperatures.
- Heat resistance, thanks to the thermal conductivity of carbon fiber favors homogenous heat distribution
Carbon PEEK finds several applications in a wide variety of industrial sectors. In addition, it is used in certain areas where an additional increase in mechanical performance is a key requirement.
Nylon 4,6
The applications of Nylon 4,6 covers engine components such as cooling systems, brakes, and transmissions. This is because Nylon 4,6 was primarily developed in order to have a much higher operating temperature than other well-known nylon grades.
This makes Nylon 4,6 have several advantages over other grades, including:
- Higher heat distortion temperature than Nylon 6,6 or Nylon 6
- Short cycle times
- Higher crystallinity results in better resistance to chemicals, especially acidic salts
However, Nylon 4,6 is not without a few disadvantages, the most notable of which is its similar moisture absorption characteristic to Nylon 6,6. But even in this regard, Nylon 4,6 has a minor dimensional increase and a high processing temperature. This makes it one of the best grades of nylon today.
Nylon 6,6
Nylon 6,6 is actually the more crystalline form of Nylon 6. Also written as Nylon 6/6, Nylon 66, or Nylon 6-6, this nylon grade has enhanced mechanical properties thanks to its more orderly molecular structure.
Nylon 6,6 – which a few refer to as PA 66 or polyamide 66 – has lower water absorption rates and significantly improved temperature resistance for machining. The standard Nylon 6 cannot be compared to PA 66. Some of the applications in which Nylon 6,6 is utilized include:
- Slide bearings
- Wear pads
- Guide wheels
Nylon 6,6 also has several advantages, the most notable of which is that its yield strength is much higher than the standard Nylon 6 as well as Nylon 610.
Nylon 6-6 also has the following beneficial characteristics:
- Rigidity
- High strength
- Low coefficient of friction across a wide range of temperatures
- Toughness
Nylon 6,6 is also resistant to chemical reagents, oil, and solvents.
Nevertheless, Nylon 6,6 has a few disadvantages, which include:
- Minimized impact strength within a dry environment
- High hygroscopicity
- Controlling the molding process is quite challenging.
Surface Finishes You Need to Know for Plastic Injection Molding
At times, there’s a need for custom injection molded plastic components with several surface finish options that will accommodate the roughness a particular part needs.
The Society of the Plastics Industry has set the standards for the United States plastic industry. Here are the 12 grades of surface finishes within the following four categories:
- Grade A – Glossy Injection Molding Surface Finish
Creating a shiny and super-smooth finish on compatible custom plastic injection molded components requires the use of a diamond buff polisher.
- Grade B – Semi-Glossy Injection Molding Surface Finish
Emery cloth or ultra-fine grit sandpaper always leaves some sheen to the polymer product for plastic components that require glossiness. This ensures the thermoplastic components won’t show machining marks or tools.
- Grade C – Matte Injection Molding Surface Finish
Grit sanding stones remove every machining mark while creating a matte-to-dull finish on injection-molded plastic components.
- Grade D – Textured Injection Molding Surface Finish
Plastic components generally undergo sandblasting processes when a textured or rough finish is required. In addition, mechanical applications that guarantee increased friction usually require materials with this finish.
The Benefits of Custom Plastic Injection Molding
Plastic injection molding has maintained its top spot as one of the most prominent versatile methods for producing plastic components. Custom plastic injection molding is a more reliable and straightforward process than others but offers these remarkable benefits you need to know:
- Improved strength
- Minimized waste
- Incredibly high efficiency with super-fast production
- Flexibility of color and material options
- Reduced labor costs over other types of plastic molding
- Complex component design with an ultra-high level of consistency
Choosing the Right Injection Molding Material for Your Own Project
As you may already know, injection molding is a broad field with vast material options. This can be somewhat overwhelming, and even professional product developers are not left out.
Here’s a brief selection guide that should point you in the right direction, especially when it comes to choosing the material for your own plastic injection molding project.
You can choose your plastic injection molding materials based on the following:
- Material hardness: Thermoplastic Polyurethane and Nylon grades perform exceptionally well for high-performance and hardness-related applications.
- Cost: The best options are Polypropylene and Polycarbonate
- Flexibility: Polypropylene is the most suitable candidate for applications requiring incredibly high flexibility needs.
- Temperature resistance: Acrylonitrile Butadiene Styrene and Nylon are perfect options that maintain their material properties and shape at high temperatures.
- Applications: The intended applications will determine the type of material you select for your own plastic injection molding project.
Conclusion
It is believed that this brief overview has opened your mind to some of the popular – and not-so-popular – kinds of materials used for plastic injection molding processes, including their properties as well as applications. In addition, you can modify any of these materials using glass fibers, lubricants, and even U stabilizers if you want custom materials for your own unique project needs.