The shrinkage characteristics of plastics are one of the inherent properties of plastics, which play an important role in dimensional stability and precision of plastic parts. The shrinkage characteristics of plastics include the thermal shrinkage of plastics, elastic recovery, plastic deformation, post-shrinkage and aging shrinkage. It is expressed as a change in linear shrinkage and volume shrinkage that occurs during the molding process and during use, and is usually expressed as a shrinkage characteristic value.
There are currently four materials commonly used for precision injection molding:
(1) POM and carbon fiber reinforced (CF) or glass reinforced (GF). This material is characterized by good creep resistance, fatigue resistance, weather resistance, dielectric properties, flame retardancy, and easy release of the lubricant.
(2) PA and glass fiber reinforced PA66, its characteristics: strong impact resistance and wear resistance, good flow performance, can form 0.4mm wall thickness products. Glass fiber reinforced PA66 has heat resistance (melting point of 250 °C), which has the disadvantage of being hygroscopic, and is generally subjected to humidity control after molding.
(3) PBT reinforced polyester with short molding time. The molding time is compared as follows: PBT ≤ POM ≈ PA66 ≤ PA6.
(4) PC and GFPC. Features: good wear resistance, enhanced rigidity, improved dimensional stability, weather resistance, flame retardancy and good formability.