Low Density Polyethylene (LDPE) By Kyle Hanley

LDPE Physical qualities Maximum Temperature: 176 °F (80 °C) Minimum Temperature: −58 °F (−50 °C) Melting Point: 248 °F (120 °C) Tensile Strength: 1700 psi (11.7 MPa) Hardness: Shore durometer (SD)55, (hard hat=75, chewing gum=25) UV Resistance: Poor Translucent Excellent flexibility Density: 0.92 g/cm³

LDPE It has more branching (on about 2% of the carbon atoms) than HDPE, so its intermolecular forces (instantaneous- dipole induced-dipole attraction) are weaker, its tensile strength is lower, and its resilience is higher.

LDPE Production The first of the polyolefins, Low Density Polyethylene (LDPE) was originally prepared about fifty years ago by the high pressure polymerization of ethylene. Typical operating pressures of 30,000 to 45,000 psi Typical Operating Temperatures to 600°F (316°C)

LPDE Production Pressure Vessel for LPDE production

LDPE Chemically LDPE is unreactive at room temperature, great choice for containers. Although it is slowly attacked by strong oxidizing agents and some solvents will cause softening or swelling. (Hydrocarbons, Mineral Oils and Oxidizing Agents )

LDPE LDPE Fabrication: Weldable and machinable Good for parts that require flexibility Trays & containers Food storage and laboratory use acceptable Very soft and pliable

Bottles made from LDPE LDPE is a good choice for the aseptic packaging of pharmaceutical products such as ophthalmic medications. The Blow Fill Seal (BFS) process is a popular packaging operation for these products, and LDPE makes an excellent choice for a container material.

LDPE LDPE granules come into the production facility in the form of little pellets.

The Extrusion Process The Raw LDPE granules are feed into a hopper which supplies the extruder screw.

The Extrusion Process The friction between the feed screw flights and the barrel generate up to 85% of the heat needed to keep the polymer in melt during the extrusion process. The extruder barrel which houses the extruder screw has heating bands around the outside of it which help keep the polymer in melt during process startup.

The BFS process After the polymer melt is pushed through the feed screw, the melt then turns downward and flow through a die to form a parison that the container dies will then clamp onto.

The BFS Process Thermoplastic resin is extruded into a tubular shape called a parison.

The BFS Process When the parison reaches the proper length, the mold is closed and the parison is cut. The bottom of the parison is pinched closed and the top is held in place. The mold is then conveyed to a position under the blowing and filling nozzle.

The BFS Process The blow-fill nozzle is lowered into the parison until it forms a seal with the neck of the mold. The container is formed by blowing sterile filtered compressed air into the parison and expanding it against the walls of the integrally cooled mold cavity. Next, the sterile air is vented from the container and the sterile product is metered into the container through the fill nozzle, which then retracts.

The BFS Process Separate sealing molds close to form the top and hermetically seal the container.

The BFS Process The mold opens, and the formed, filled and sealed container is conveyed out of the machine.

Blow Fill Seal Animation of the BFS process

LDPE containers Translucent Soft and pliable so that the contents are easily emptied. Lower strength (compared to HDPE) makes for easier cap removal.

Container Integrity If any leak is present, the discharge current will flow through the pinhole into the container and the detection of this current will automatically cause the container to be rejected.

Recycling The cut out pieces of the containers are then collected and put through a regrinder. Those pieces of regrind can be put back into the feed hopper and the process can start over again.

Conclusion LDPE has certain properties which make this polymer very favorable for single unit dose packaging of medications. LDPE can easily be recycled so that the waste is minimal. LDPE is relatively easy to work with for the BFS molding process when compared to other possible packaging materials.

End of Show Have a good day!!!