U polymer

Precautions in molding, Technical support

Injection molding and drying conditions for U polymers, and precautions in molding

(Revision B, July, 2020)

1. If the cylinder temperature indicated above is not high enough to provide the material with desirable flowability, the temperature may be raised up to the limit temperature to improve flowability.
2. Proper setting of the screw back pressure is effective for improving blending efficiency and for removal of gases, and thus make sure to set a suitable back pressure.
3. If a hot-air-circulating tray drier is used, place and dry the pellet in a layer with a thickness of 3 cm or less under the condition above.
4. Use of a dehumidifier, reduced-pressure or vacuum type drier allows more efficient drying.
5. The water content of the resins other than the AX series should be less than 200 ppm, and those of the AX series, less than 2000 ppm.
6. Make sure to heat the hopper immediately above molding machine, for example, by employing a hopper drier, for the purpose of raising the temperature of the pellets therein to the drying temperature and preventing them from absorbing moisture.
7. As the resins are ester resins, presence of excessive water leads to hydrolysis of the resins during heat processing, decrease in the molecular weight of the resins, and consequently decrease in the quality of molded products. Comply strictly with the drying condition indicated above, and take notice of reabsorption of water during molding.
8. Lower mold temperature may result in residual strains at the sharp edge and gate portions of the molded products, which may results in cracks. Make sure to raise the mold temperature (mold surface temperature actually determined) into the range of temperature indicated above as standard.
9. Select a suitable molding machine so that the amount of resin injected per shot is equivalent to 30 to 70% of its cylinder capacity.
10. If a resin remains in the molding machine for 10 minutes or more, remove the resin thoroughly form the molding machine and then restart molding. If not, products in poor appearance such as burns and silver may result.
11. Note that antirusts and other oils remaining adherent to the mold may cause cracks in the products.
12. If there remains hazes on the surface of molded products of AX series resins, raise the temperature of mold and cylinder and make sure to remove gases in the mold thoroughly.

Extrusion molding of U polymers

See the table above for the settings of barrel temperature and the conditions of drying resins.
Contact our sales department for details.

Technical support

1. At our resin technical center, we accept molding trial production by bringing in molds.
   Owned equipment: THE JAPAN STEEL WORKS, LTD., Vacuum degassing system with starve feed "J Melter"
2. We can also propose mold design by CAE resin flow analysis.