Materials that are compatible with plastic prototype injection molding are known as thermoplastics. Within thermoplastics, there are approximately 70 different types. Commonly known types include polycarbonate, polypropylene, nylon, etc. Each thermoplastic type has a set of unique characteristics and usage scenarios that distinguishes itself from other types. Material selection for a part can be challenging because the engineer must be familiar with the 70 different types and know which type to select for the particular application.For example, polycarbonate would be an ideal type to select if a part requires transparency and high strength. Once the type is selected, the next step would be to select a particular grade of material. Websites such as matweb.com and ulprospector.com are helpful plastic resin databases that make it possible to select a particular grade.Continuing to use the polycarbonate example previously discussed, we find that there are over 6000 grades of polycarbonate available. Selection of a particular grade requires a review of the part design and its product requirements such as mechanical, cost, tolerances, environmental conditions, assembly, sterilization, regulatory, aesthetics, and any special requirements.For example, this polycarbonate part may be a relatively thin wall part requiring a high melt flow grade. It could also be a medical part requiring gamma sterilization, requiring an additive to prevent color shift. These requirements can be searched on matweb.com and ulprospector.com to compile a list of the grades that meet those requirements. The final step would be to contact the distributors of those material grades for pricing and availability, then place an order for the selected grade of polycarbonate.