How to Use PRIMACOR-Extrusion:Technical Information
Feed Zone Temperature
Because of the relatively low melting points of PRIMACOR* copolymers, feed zone temperatures must be lowered (versus LDPE) to prevent bridging in the feed throat and hopper. Feed zone temperatures in the range of 300-400° F (149-204° C) are suggested for polymers 3-12 wt% acrylic acid (AA). Even lower temperatures may be necessary for polymers in the >12 wt% AA range (e.g. 280° F).
Fabrication Temperatures
Specific fabrication temperatures depend on the fabrication technique, melt index, and acrylic acid content of the copolymer.
Polymer
|
Fabrication Method
|
Suggested Melt
Temperature Range
|
 |
|
3-12 wt% Acrylic Acid (AA)
<12 MI
|
Blown Film Extrusion
|
275-425° F
(135-218° C)
|
|
3-12 wt% AA
<12 melt index
|
Cast Film Extrusion
|
350 - 550° F
(176-288° C)
|
|
3-12 wt% AA
5-10MI
|
Extrusion Coating & Laminating
|
500-580° F
(260- 304° C)
|
|
3-12 wt% AA
>10 MI
|
Extrusion Coating & Laminating
|
400-450° F
(204-232° C)
|
>12 wt% AA
>100 MI |
Extrusion Coating & Laminating |
320-350° F
(160 -176° C) |
3-12 wt% AA
<12 MI |
Injection Molding |
350-450° F
(176-232° C) |
3-12 wt% AA
>12 MI |
Injection Molding |
300-425° F
(148-218° C) |
20 wt% AA
100-1300 MI |
Hot Melt Adhesives |
375-400° F
(190-204° C) |
|
Operating Practices
Precautions should be taken during melt processing to prevent undue equipment wear and to minimize the generation of unwanted cross-linked material:
- All metal surfaces that come into contact with the adhesive polymer should be constructed from corrosion-resistant materials, such as chrome or nickel-plating
- Oxidation can cause cross-linking and polymer degradation. Be sure to keep the feed throat full to minimize exposure of the melt to the air.
- Do not shut down equipment when PRIMACOR copolymers are in the extruder. Because of their excellent adhesion to metals, PRIMACOR copolymers may stick to the screw and degrade if left idle at hot temperatures, increasing purge time when the extruder is restarted.
- Because PRIMACOR copolymers do not absorb moisture, conventional packaging and handling practices can be used. There is no need to dry the polymer before use.
- Run a purge resin such as LDPE through the screw while the extruder is heating, and before it is shut down.
Purging
Because PRIMACOR copolymers have excellent adhesion to metals, thorough purging of equipment is necessary.
- Be sure to purge with an LDPE that has a lower melt index (higher molecular weight).
- Do not raise temperatures to the set point of the next resin until all PRIMACOR copolymer is purged.
- Reduce purge time by maximizing screw speed. Keep the extruder "slow-rolling" (10-15 rpm), rather than idled.
Dow Technical Service personnel can help you resolve purging problems. Just call 1-800-888-8DOW (8369) for more information or contact us.
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