Extrusion
“Extrusion is a process used to create objects of a fixed cross-sectional profile. A material is pushed or drawn through a die of the desired cross-section..” Wikipedia, Extrusion, 7/23/2010
“In the extrusion of plastics, raw thermoplastic material in the form of small beads or pellets is gravity fed from a top mounted hopper into the barrel of the extruder. Additives such as colorants and UV inhibitors (in either liquid or pellet form) are often used and can be mixed into the resin prior to arriving at the hopper.” ”The material enters through the feed throat (an opening near the rear of the barrel) and comes into contact with the screw. The rotating screw (normally turning at up to 120 rpm) forces the plastic beads forward into the barrel which is heated to the desired melt temperature of the molten plastic (which can range from 200 °C/400 °F to 275 °C/530 °F depending on the polymer). In most processes, a heating profile is set for the barrel in which three or more independent PID controlled heater zones gradually increase the temperature of the barrel from the rear (where the plastic enters) to the front. This allows the plastic beads to melt gradually as they are pushed through the barrel and lowers the risk of overheating which may cause degradation in the polymer.” Wikipedia, Extrusion, 7/23/2010
“Extra heat is contributed by the intense pressure and friction taking place inside the barrel. In fact, if an extrusion line is running a certain material fast enough, the heaters can be shut off and the melt temperature maintained by pressure and friction alone inside the barrel. In most extruders, cooling fans are present to keep the temperature below a set value if too much heat is generated. If forced air cooling proves insufficient then cast-in heater jackets are employed, and they generally use a closed loop of distilled water in heat exchange with tower or city water. Wikipedia, Extrusion, 7/23/2010
”After passing through the breaker plate molten plastic enters the die. The die is what gives the final product its profile and must be designed so that the molten plastic evenly flows from a cylindrical profile, to the product's profile shape. Uneven flow at this stage would produce a product with unwanted stresses at certain points in the profile. These stresses can cause warping upon cooling. Almost any shape imaginable can be created so long as it is a continuous profile.” Wikipedia, Extrusion, 7/23/2010
Applications
Coextrusion
Composites Extrusion
Extruders
Extrusion Blow Molding
Extrusion Casting Film
Extrusion Coating
Extrusion Dies
Extrusion Manufacturing
Extrusion Mixing
Extrusion Modeling
Gear Pumps
Kneaders
Processing
Profile Extrusion
Pultrusion
Reactive Extrusion
Rubber Extrusion
Single Screw Extrusion
Solid-State Extrusion
Twin Screw Extrusion
Ultrasonic Assisted Extrusion
Vibration Assisted Extrusion
Water Assisted Extrusion
Recent US Patents
10/19/2010
7,815,386
Device for storing and extrusion of a flowable substance
Sogaro of Dentaco Dentalindustrie-und Marketing, Germany has developed a device for the storage and extrusion of a flowable substance including a loading unit for an application tool. (RDC 1/18/2011)
9/28/2010
7,803,303
Methods and apparatus for plugging honeycomb structures
Hagg of Corning Incorporated has developed a method for plugging honeycomb structures by extrusion through an extrusion plate with holes matching the honeycomb channels for plugging. (RDC 12/8/2010)
Review Articles
Review: Single Screw Extruder in Particulate Filler Composite
(395 – 403) Polymer - Plastics Technology and Engineering 50 #4 (2011)
Ariffin and Ahmad of the Universiti Sains Malaysia, Malaysia, reviews single screw extruder research of particulate filled composite. This review includes factors effecting processing of particulate filled composite using a single screw extruder. The mixing requirements for a particulate filled composite is analyzed and discussed in terms of single screw extrusion. The factors for achieving effective mixing of this type of composite are also discussed. (RDC 3/25/2011)