Plastic material selection for injection molding is critical for plastic part design for a product. Selection of the type of plastic material affects plastic part design, performance, and tool & manufacturing cost.
This article covers the plastic material selection process and common thermoplastic materials. This guide will help mechanical design engineers in the best thermoplastic plastic material selection for their products.
Types of Plastics Grades
Thousands of types of plastic material grades are available in the market. But only a few commercial-grade plastic materials are widely used to manufacture plastic parts using injection molding. Following are some of the widely used plastic materials in injection molding.
- Acrylonitrile butadiene styrene (ABS)
- Polycarbonate (PC)
- ABS + PC blend
- HDPE (High-density polyethylene)
- Polypropylene (PP)
- Nylon (PA 6, PA 66, PA 11)
- PEEK
- Polystyrene (PS)
- Delrin (POM)
All of the above materials are available in various grades. Different grades have different properties and characteristics.
Factors affecting Selection of Plastic Material For Injection Molding
You should consider the following points during plastic material selection for a given application.
- Product working temperature.
- Structural strength requirements: mechanical properties requirement
- Cost constraints.
- Weight constraints.
- Plastic part design.
- Product aesthetic requirements.
- Assembly process.
- Type of application: indoor or outdoor.
To fulfill the above plastic part design requirements. The following properties of plastic material are analyzed.
1. Material Thermal Properties
Following thermal requirements of a product has impact on material selection.
- Product maximum and minimum working temperature.
- Heat dissipation during product operation
- HDT temperature (Heat deflection temperature)
- Melting temperature
For example, if the product’s working temperature is 50°C and it is dissipating heat. PC or glass-filled PC is a good choice instead of ABS.
2. Material Physical Properties
We should consider the following physical properties of plastic materials during the plastic material selection process.
- Impact resistance
- Tensile strength
- Wear resistance
- Material strength and stiffness etc.
- Creep resistance
You need to analyze the above physical properties of plastic material on the following parameters.
- Static and dynamic loads acting on the part.
- Wear resistance.
- Continuous loading or creep.
For example, Engineers recommend nylon or POM materials for moving parts such as gears and screws because of their self-lubrication properties.
3. Injection Molding Capability
Thermoplastic material following processing or mold-ability properties also impacts plastic material selection.
- Material melting temperature
- Melt flow rate
- Shrinkage
- Dimensional stability.
4. Injection Molded Part Aesthetics and Dimensional Accuracy
Plastic material selection also has an impact on part aesthetics and dimensional accuracy. For example, ABS material gives good dimensional accuracy and Finish. Therefore engineers recommend ABS material for manufacturing indoor consumer electronics products.
Click this Link to know plastic material recommendations for the required SPI surface finish.
5. Exposure to Chemicals
You should also consider the exposure of the product to different chemicals. For example, Nylon and acetal are generally suitable for industrial environments.
6. Exposure to outside Weather (Weather Resistance Properties)
Outside Temperature, moisture, and UV exposure affect plastic part properties and appearance. Therefore you should select a material that can withstand outside weather conditions for outdoor products.
For example, UV Radiation causes yellowish color on plastic parts or can degrade plastics. Therefore use UV additives or UV-stabilized plastic material if the product can expose to UV radiation.
7. Assembly Process
The part assembly process also has an impact on plastic material selection. For example, adhesive manufacturers recommend ABS and PC materials for plastic part assembly using adhesives.
Whereas for Nylon and HDPE special adhesives are required. PP and ABS are easy to ultrasonic weld compared to Nylon and PC.
Injection Molding Materials
| Material | Properties |
|---|---|
| ABS |
|
| PC (Polycarbonate) |
|
| ABS+PC |
|
| PP (Polypropylene) |
|
| Nylon (PA 6, PA 66, PA 11) |
|
| Delrin (POM) |
|
| HDPE (High Density polyethylene) |
|
| PEEK |
|
| PS (Polystyrene) |
|
To sum up, the Plastic material selection process for injection molding is a critical part of product design. The type of material used ensures product quality, performance, and cost. Consider product all functional and certification requirements before the selection of material.
We will keep updating more information on plastic material selection for injection molding. Add your suggestions, comments, or questions in the comment box.
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