Polymer & Plastics Extrusion Equipment
Diamond America has over 20 years of experience in custom extruder design for polymers and plastics, including expert 3D modeling and Finite Element Analysis (FEA) software systems to optimize die and extruder performance and quality.
Plastics extrusion equipment is used for continuous, high-volume manufacture of a wide range of final products that have constant cross section, such as plastic pipes, frames, sheeting and films.
Critical Factors Design Of Polymer Extrusion Equipment
Compression Ratio
The compression ratio is the ratio of the screw depth at the feed zone by the hopper, to its depth at the metering zone by the die. Compression ratio varies greatly according to the polymer that is being processed. For example, where rigid PVC requires a compression ratio of around 2.3:1, polypropylene or a more slippery material requires a ratio of nearer 4:1. The compression ratio is also impacted by the relationship of cross sectional areas at the screw feed and metering points. Finally, barrier designs, mixers, and variable lead screws affect not only the compression ratio, but the final screw output as well. The design of polymer extrusion equipment is indeed a very specialized process.
Die Design
Due to the wide variety of products, ranging from plastic pipes to films, polymer extrusion die design is very diverse and complex and includes dies for:
- Blown Film extrusion
- Sheet and Film extrusion
- Tubing extrusion
- Over Jacketing extrusion
- Co-extrusion
- Extrusion Coating
Prevention of die swell must be built into the die design by:
- Blown Film extrusion
- Sheet and Film extrusion
- Tubing extrusion
- Over Jacketing extrusion
- Co-extrusion
- Extrusion Coating
Dies have to be carefully designed to handle the specific behavior of plastic extrusion melts. Polymers consist of long chains of molecules which become aligned and oriented in a single direction when forced through a die. On release, they tend to diverge randomly when no longer constrained, causing a phenomenon known as ‘die swell’.
Examples of Polymer and Plastic Extrusion Applications, Materials and Selection Criteria
Building & Construction
Rainwater Pipes, Gutters
Soffits, Fascias
Windows, Doors
Door Seals
Garden Fencing
Rigid PVC
Compact/foamed PVC
Rigid PVC
Co-extrusion
Polystyrene/polyethylene
Strong, UV resistant, color fast
UV resistant, color fast
Appearance, can be cut and welded
Dual properties in one molded profile
Recycled material, does not require painting
Electrical
Light Diffusers
Conduit and Cable Protectors
Cable Harnesses
Acrylic
Rigid PVC
PTFE Filled PVC
Optical properties
Tough, good insulator, chemically stable
Flexible, resistant to chaffing
Household Goods
Curtain Tracks
Fridge Seals
Rigid PVC
Rubber, PVC and metal
UV resistant, tough material, can be colored
Can be magnetized
Medical
Drip Tubes, Catheter Tubes
Plastic composites
High integrity, reinforced, can be sterilized
Packaging
Aerosol and Spray Dip Tubes
Polyethylene
Transparent, stable, chemically resistant
Utilities
Gas Pipes, Water Pipes
Soil Pipes
Polyethylene
Rigid PVC
Corrosion resistant, good integrity
Strong, can be joined using solvent cements
Diamond America Extrusion Test Facility
Diamond America provides a fully equipped test facility for new product process and formulation testing for all applications. The test laboratory boasts several table top extruders for small batch scaled production, as well as full scale twin feed and bulk extruders. Experienced engineers are on hand to assist with extruder customization, die design, system controls and the selection of associated extrusion equipment.
