Extrusion Equipment and Process

In a paste extrusion line for wire insulation, the wire is passed through the paste extmder where it is coated with PTFE while moving through the die. It 

The ram extruder for this process is a special unit and can be either horizontally or vertically oriented, which refers to the direction of the ram movement. The extmder consists of a heated barrel where the preform is loaded, and a hydraulic or screw-driven ram. The conductor is drawn by a power system through a hollow mandrel located at the center of the barrel. The mandrel terminates in a wire guide tube. 

The preform frbrillates in the die under ram pressure and forms an extmdate, which should have the right thickness and smoothness. The preform is pressed through the extmder cylinder (barrel) with little pressure development until it reaches the die, where the cross section area for the passage of the preform decreases by the angular design of the wall (Fig. 5.29). 

The polymer must be heated to above its melting point of 342°C for a brief period of time for melting to occur. The oven temperatures are typically set at 400°C-600°C, based on a number of variables including the speed of the wire and thickness of the coating. Heat transfer to the polymer accelerates at these temperatures, but care must be taken to prevent exposure of PTFE to temperatures above 380°C where degradation begins to speed up. 

The wire is usually allowed to cool by natural convection in the ambient air. Blowers can be installed to move the warm air away from the area. 

---

These families of resin are produced in commercial scale high pressure processes. To produce these types of polymers, additional investment is needed, e.g. in corrosion protection, refrigeration capacity, extrusion equipment and process units to recycle the comonomers after purification back into the process. 

The majority of thermoforming production is by roll fed machines. Sheet fed machines are used for the smaller volume applications. Larger production units have in house sheet extrusion equipment. Because of the complexities in synchronising sheet extrusion equipment and the thermoforming machines, the two processes can be carried out independently of each other, the extruded sheet being produced in advance of production schedules. 

Cheremisinoff N, Polymer Mixing and Extrusion Technology, Marcel Dekker, New York, 1997. Todd DB ed.. Plastics Compounding—Equipment and Processing, Hanser Publishers, Munich, 1998. 

All GRTP can be extruded. Processing parameters will vary with resin system, percent glass filler, extrusion equipment, and part design. The suggested processing parameters for polyacetal are presented in Table 4-7. 

A description of the basic processing and equipment used in ceramic tile manufacture is included below to familiarize the non-ceramist with the basics of this technology. With few exceptions, the equipment and processes used in diy pressing and/or extrusion of ceramic tile are similar to those used in all parts of the ceramic industry and will not be repeated for other areas. 

Much of this work was carried out at the Ameriean Leistritz Extrader Corporation Somerville, NJ process laboratory. The authors would like to thank Leistritz for the use of their PLA extrusion equipment and their expertise in PLA extrusion. 

Acetal resins may be processed without difficulty on conventional injection moulding, blow moulding and extrusion equipment. The main points to be considered are ... 

Polyaryl ether ketones may be processed on conventional injection moulding and extrusion equipment, providing sufficiently high temperatures can be achieved. Melt temperatures required are typically 370°C for unreinforced PEEK, 390°C for reinforced PEEK and both unreinforced and reinforced PEK and unreinforced PEEKK, and 410°C for reinforced PEEKK. For the latter material a temperature profile from feed zone to nozzle would be... 

For uniform and stable extrusion it is important to check periodically the drive system, the take-up device, and other equipment, and compare it to its original performance. If variations are excessive, all kinds of problems will develop in the extruded product. An elaborate process-control system can help, but it is best to improve stability in all facets of the extrusion line. Some examples of instabilities and problem areas include... 

One type of block polymer is known as thermoplastic elastomers. They consist of a number of rubber blocks tied together by hard crystalline or glassy blocks. These materials can be processed in injection molding and extrusion equipment since the crystalline blocks melt or the glassy ones soften at high temperatures. However, at lower temperatures, such as at room temperature, the hard blocks behave very much as cross-links to reduce creep and stress relaxation. Thermoplastic elastomers have creep behavior between that of very lightly cross-linked rubbers and highly cross-... 

A comparison is made between a 3.5 melt flow conventional polypropylene homopolymer (Profax 6523) and a 7.0 melt flow, high-melt-strength, foamable PP homopolymer in extensional flow. The importance of extensional or elongational viscosity in the foam process is demonstrated and the way in which the rheological differences permit the production of low-density foam on tandem extrusion equipment is shown. 6 refs. 

Dow Plastics is to unveil a new resilient polyolefin foam, Strandfoam, which offers packagers of lightweight electronic equipment and components reduced package size, and savings in materials and shipping costs. Strandfoam is made of a special blend of PE and is produced by a proprietary extrusion process that yields fused strands of closed-cell foam with a network of air channels parallel to the foam strands. Strandfoam provides the required levels of protection with substantially smaller volumes of foam compared to urethane. 

Ecovio FS Paper is also a compound of Ecoflex FS and PLA with a very high content of renewable resources. This grade was optimized for extrusion coating of paperboard. It can be processed on standard PE equipment and shows an excellent adhesion to card board and paper. The Ecovio coating forms a barrier for fat vegetable and mineral oil, liquid and aroma. Applications of choice are compostable paper cups for hot and cold drinks, freezer boxes or paper wraps for snacks. 

---