A starting point One way to begin is to study similar existing applications to learn which materials, processes, and designs have worked successfully. Next, discuss the application with experienced molders, mold builders, and materials manufacturers and compounders to get their recommendations. Finally, try to select the best plastic for the application by comparing the relevant properties of each material that has been recommended. The brief summaries presented here indicate property highlights and characteristics of the most common families of thermoplastics and thermosets used in industrial and consumer products. Fillers usually decrease cost, increase stiffness, improve dimensional stability and reduce shrinkage.
Plasticizers increase flexibility and reduce most strength properties.
Copolymers can have either higher or lower properties and cost depending on the monomers used and their proportions. A prototype plastic part cannot duplicate exactly the performance of an injection-molded production part unless it is molded in a production environment in a production mold. This is normally impractical, so the best that can be expected is an approximation of a production part. The fastest and most economical way to produce plastic prototypes is to machine them from slab or bar stock. But stock forms of plastics are made by extrusion, not injection molding.