Processing
Plexar resins should be processed under similar conditions as the unmodified resin. A minimum temperature of 400° F is recommended to obtain good adhesion. EVA-based materials should have a melt temperature of 450° F or less, as EVA resins are more sensitive to degradation than other polyolefins. Typical process temperatures are 400-450° F. It is important to have adequate ventilation to prevent fumes from collecting. Plexar resins should not be allowed to remain in the extruder during shutdown. Purging with LDPE is generally recommended. Plexar PX 909 can be used for purging EVOH or nylon followed by LDPE.
Processing conditions can have a significant impact on adhesion.
In most cases, adhesion reaches a plateau value at which point a further increase does not cause a change in adhesion. Also, in most cases, the relationship is not linear. Therefore, adhesion can change significantly with a small change in process conditions. It is important to test adhesion under the most severe conditions.
Handling
Plexar resins are supplied as free-flowing pellets or specialty powder grades and should be handled within accepted industry practices for polyolefins. When not being used, the container and liner should be closed. A Material Safety Data Sheet for Plexar resins should be consulted for other handling guidelines.
Storage
Plexar resins should be stored in a cool, dry place. When stored properly, Plexar resins have a shelf life of at least 18 months. If exposed to significant levels of moisture, some loss in adhesion may occur. Plexar resins should be stored in closed bags and not subjected to high levels of moisture. Drying of Plexar resins is generally not required. Your Equistar technical representative should be consulted for specific recommendations if the resin becomes wet, or it is believed the resin may have been exposed to high moisture levels for an extended time.
Purging
An improper shutdown while purging can lead to significant gel issues. A shutdown should be done using a resin other than Plexar, such as LDPE. Typically, an extruder should not be allowed to idle more than 30 minutes when containing Plexar resin and even then a small amount of throughput is recommended. Plexar PX 909 is an effective purge for EVOH and nylon but should not be left in an extruder that is idle or will be shut down.
Regulatory Information
Most Plexar resins meet the requirements for the Food and Drug Administration regulation 21CFR 175.105 for adhesives. This regulation describes adhesives which may be safely used as components of articles intended for use in packaging, transporting or holding food in accordance with conditions outlined in that section. For an adhesive formulation to be used in compliance with Section 175.105, the formulation must be used under conditions that prevent its becoming a component of food in more than insignificant, de minimis, amounts. Please contact Equistar’s Product Safety Representative for more information.