DRYING CONDITIONS

Most Nylon manufacturers ship NYLON 66 resins at or below 0.25% moisture content. When drying is required due to hopper residence times in excess of one hour, exposure to air, or when adding regrind, desiccant air dehumidifying hopper dryers are necessary. Hot air dryers without desiccant should not be used as they can actually increase the moisture content of the resin. The temperature of the drying air should not exceed 165°F for natural colored resins and 180°F drying temperature allowable for black materials in order to prevent excessive oxidation and discoloration. The required drying time is dependent on the length of time the resin is exposed to the atmosphere and the level of humidity. The following drying times are commonly recommended.

Optimum moisture levels range from 0.08% to 0.18%. Moisture levels less than 0.06% can result in reduced flow characteristics and/or poor surface aesthetics. Moisture should be measured via the Karl-Fischer Titrator method. Weight Loss or Desiccating weight loss units can be acceptable for the manufacturing environment, but they should be correlated via the Karl-Fischer Titrator method. The dew point of circulating air should be less than -20°F (-28°C). Air throughput minimum of 1 CFM/pound of resin/hour.

INJECTION MOLDING CONDITIONS

In order to obtain high quality molded parts, the processing setup must be aligned with the specific material, molding machine, throughput rate, and part-runner configurations. Screw designs and heat transfer characteristics vary between machines of different manufacturers, making it difficult to specify cylinder temperature profiles that can be universally applied to all injection units without some modifications. The following molding conditions are recommended starting points.

*Pressures given are in the hydraulic circuit