Commom Plastic Injection Material Features

In this section, we will continue to talk about the plastic material features, hopping that will be helpful for you to make good choice of machines and raw material when producing relevant plastic products.

Polyamide (PA)

PA is featured with high fatigue strength and rigidity, good heat resistance, low friction coefficient and good wear resistance. It is generally suitable for wear-resistant force-resistant transmission parts working under medium load, temperature ≤100~120℃, no lubrication or less lubrication conditions.

  • Large hygroscopicity, moisture absorption after the decline in fluidity, prone to bubble, silver wire and other drawbacks. It should be dried before injection, drying temperature 70~80℃, drying 4~6 h..
  • Shrinkage rate range is large, prone to shrinkage hole, dent, deformation and other drawbacks. Forming conditions should be stable.

The melting point of crystalline materials is high, and the melting temperature range is narrow. The thermal stability of melting state is poor. When the material temperature exceeds 300℃, and the retention time exceeds 30 min, it will be easy to decompose.

Polycarbonate (PC)

PC material has outstanding impact toughness and creep resistance. High heat resistance, and cold resistance are also very good. The embrittlement temperature up to 100℃. The bending tensile strength is equivalent to that of nylon. It has high elongation and elastic modulus, as well as outstanding impact strength. Colorless and transparent, good coloring, the heat resistance is better than nylon, or polyformaldehyde. It has good creep resistance, electrical insulation, corrosion resistance, and wear resistance. With low water absorption, small shrinkage and good dimensional stability, it can be used  for various gears, worm gear, rack, cam, bearing, mandrel, pulley, transmission chain, nut, washer, pump impeller, lampshade, container, etc.

It is not good for resistant of Alkali, ketones, amines, aromatic hydrocarbons. Stress cracking may occur, and stress concentration (and internal stress) is easy to occur, which requires high forming conditions. It is easy to hydrolyze at high temperature and has poor melting property with other resins. The fluidity is poor, and the fluidity is sensitive to the temperature change. The cooling rate is also fast.

  • Hopper dryer temperature is very important to control the quality of plastic parts, becuase low temperature will cause lack of material, or surface luster, while high temperature will cause silver wire dark strip.

When polycarbonate contains moisture, it can seriously affect the flow properties of the material. So it must be dried, generally at 110~120℃ temperatures for 6~15 h.

Phenolic resin (PF)

PF is featured with high mechanical properties, high rigidity, low cold fluidity, high heat resistance (more than 100℃) and very low friction coefficient under water lubrication (0.01~0.03). It has good electrical properties and the ability to resist acid-base erosion. It is not easy to deform because of the change of temperature and humidity, and it is easy to form and low cost. It is used to make ashtray in automobile interior parts.

The disadvantages of PF are brittle nature, limited tone, poor light resistance, less arc resistance or resistance to strong oxidizing acids.

Polyformaldehyde (POM)

POM is featured with good overall performance including high tensile strength, impact toughness, rigidity, fatigue strength and creep resistance. WIth good dimensional stability, small water absorption, small friction coefficient, good chemical resistance, its performance is not less than that of nylon. It can be used as bearings, gears, cams, valves, pipe nuts, pump impeller, small parts of body chassis, car dashboard, carburetor, box, container, bar and sprayer of various copper replacement parts.

The disadvantages of POM is poor thermal stability, easy to burn. When prolonged exposure to the atmosphere it will age.

The decomposition temperature is 240 degrees, but when the temperature is over 30 minutes at 200 degrees, the decomposition occurs, resulting in stimulating and corrosive gases.

The mold temperature has great influence on the quality of plastic parts. Increasing the mold temperature can improve the concave surface and facilitate the flow of melt material. See mold temperature controller details.

After learning about the plastic material features, you may have an answer of how to select raw material and auxiliary machines for improving production efficiency. For more information, please feel free to contac with us.