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A vacuum metallizer process study was performed and the results in terms of optical density uniformity, metal adhesion, and barrier uniformity were evaluated. Gas barrier was found to be a complex function of the process parameters studied while adhesion was determined to be sensitive to testing materials as well as process parameters. Visual uniformity was found to depend primarily on metallization pressure.

Automatic screen changers are used in continuous processes where contamination can clog normal screen packs in a relatively short time compared to the production run time. Generally, if a production run can be completed without requiring a screen pack change, an automatic screen changer is not required.

Pipe and tubing is profile extrusion with dies designed to produce round cross-sections. A pipe and tubing extrusion line is like a profile line except it uses a vacuum sizing cooling unit rather than a cooling or calibration tank.

Significant discussion has centered on shear rates, shear heating, and viscous heat generation in the transition and mixing sections. This chapter demonstrates how to calculate shear rates in the extruder and die, pressure drops in the die, and provides other calculations related to single screw extruders. Derivations of the equations are beyond the scope of this book and can be found elsewhere.

How is an extrusion problem solved? Regardless of whether it is in a production, pilot plant, or research and development environment, there are numerous approaches to take, ranging from the trial and error method to implementing systematic investigative procedures.

The “Five-Step Process” is part of a total Quality Education System developed by Philip Crosby and Associates, Inc. The Five-Step Process is a procedure or process to follow to define, correct, and eliminate problems. It is used as part of a total quality program in many industries to improve product yield and quality performance.

Profile extrusion is one of the most common types of extrusion processes, producing a variety of product shapes in large volume. Any plastic cross-section requiring long lengths can be produced in a profile extrusion process and cut to the desired length.

Scaling up from one size twin screw extruder to another can always create processing issues and problems to be solved. If the preliminary product work is done on a 20- to 30-mm twin screw extruder and the product attributes are very good, the next step is to scale it up to a production machine to develop the process.

To troubleshoot and solve extrusion process problems, it is important to understand both the equipment operation and the polymer being processed. Understanding either the equipment or the polymers alone may not provide enough information to solve a particular extrusion problem. This chapter covers the definition of polymers, how they are formed, different types of polymers, and their structures.

Extrusion coating extrudes a polymer onto a substrate. Combining two inexpensive materials to make a higher performance product adds value and utility. Materials typically coated with plastic include paper, polyester, metal foils, cellophane, paperboard, cloth, and other plastics. The objective is to combine the best properties of each material into a third product that can perform a function neither of the individual products can do on their own.

Testing physical properties on standard test specimens obtained from injection molding or extruded parts is done in accordance with the procedures of either the American Society for Testing Materials or the International Organization for Standardization.

This chapter focuses on the different methods used to combine the melt streams from the various extruders to produce a coextruded structure.

What are the objectives or goals to be accomplished with the extruder in the overall extrusion process? The standard answer is to produce a quality product that meets the customer specifications 100% of the time. Although this is true, the extruder has five distinct goals or objectives to achieve in the extrusion process that will result in a quality product if done correctly.

A few potential problems exist in pipe, tube, and profile extrusion. Pipe and tubing involve a symmetrical profile extrusion. For pipe and tubing, the cooling or calibration tank has sizing rings and one or more vacuum chambers to shape the pipe to the desired outside diameter.

Gear pumps provide consistent polymer flow, which results in more consistent product dimensions. A gear pump is a positive displacement pump consisting of two gears, four bearings, internal heating, shaft seals, and very precise speed control. There are multiple sizes and speed ranges that provide multiple output ranges.

This chapter deals with the cast film process and outlines the advantages of cast film versus blown film.

This chapter discusses extrusion of polymeric materials to produce finished products for industrial or consumer applications, which is an integrated process, with the extruder comprising one component of the entire line. In some applications, the production lines are very long with numerous operators, requiring operators to communicate and work together to produce an acceptable finished product.

This chapter covers how to troubleshoot potential problems encountered with the sheet processes and possible corrective actions.

The optimum screw design depends on the polymer being processed, throughput rate, mixing requirements, venting, and die design. A well-designed screw is critical to optimize productivity, extruder control, and product yields. Improper screw designs can lead to high-frequency instabilities caused by melt temperature or pressure variations in the extruder.

The extrusion of polymeric materials to produce finished products for industrial or consumer applications is an integrated process, with the extruder comprising one component of the entire line. In some applications, the production lines are very long with numerous operations, requiring operators to communicate and work together to produce an acceptable finished product. If the extruder temperature profile is set incorrectly, the product ingredients are not properly formulated, the cooling on the extruder feed throat is not running properly, the melt temperature at the end of the extruder is incorrect, the cooling bath temperature is not set correctly, the puller at the end of the line is running at the wrong speed, or any other incorrect operating condition or combinations of conditions exist, the product may not meet customer specifications. Each step in the process adds value; consequently, the product reaches its maximum value at the end of the line. An improper setting at the beginning of the process may cause the product to be unacceptable at the end of the line after significantly more value has been added. Speeds of the different process steps must be matched to ensure product compliance.

Polymer response or behavior in the extruder, combined with the extruder processing conditions, i.e. barrel temperatures, screw speed, and screw design, allows the extruder to extrude a homogeneous polymer melt at a constant pressure and temperature.

Publisher Summary Extrusion is widely used for the continuous and intermittent manufacture of polymeric products because it permits the preparation of highly uniform polymer melts at high rates. This is necessary because the low thermal conductivity and high viscosity of polymers prevent the easy and high rate melting in bulk containers using external heat sources. There are two broad categories of extruders: single-screw and twin-screw extruders. The single-screw extruder has existed for many years and still today it is the primary form of extruder, due to the ease of production and lower equipment costs, as well as its ability to handle high torques during polymer processing. Twin-screw extruders were primarily used for polymer powder extrusion and compounding, where high-quality dispersive mixing or well-defined residence times for devolatization, temperature-sensitive polymers, and reactive extrusion. In the last step in extrusion, the molten extrudate leaves the extruder and is then shaped into the desired cross-section required in the next step of the polymer process. The three biggest potential safety hazards associated with extruders are burns, electrical shock, and falls. Without proper protective equipment, burns can be common when working around extruders. If insulation is placed around the die make sure it is in good shape and properly installed. Touching exposed areas of a hot die or handling extrudate without gloves normally causes burns. Long sleeves with properly approved thermal gloves and face masks should be worn when working around the die, changing the die, tightening die bolts, or other functions performed on the die. Hot extrudate from the extruder will stick to the skin.

Publisher Summary This chapter focuses on vacuum metallizing used in flexible packages. Metallizing is still the most dominant process in packaging and its four main areas of use are decorative or aesthetic, barrier, functional, and security coatings. Decorative coatings for packaging began with the simple metallization of polymer films and papers, which gave the web a bright metallic appearance. This bright metallic web enabled products to be wrapped, boxed, or labeled by using a material that stood out from their competitors. Various methods are used for getting the metallic look onto packages. The most commonly used method is to metallize the whole substrate, such as paper or polymer, and then print or laminate with the printing selectively over the metal to complete the desired design. Barrier coatings is very broad category and includes coatings that reduce light, oxygen, water vapor, or other gas transmittance. Barrier coatings can be divided into two main groups, opaque and transparent barrier coatings. Opaque barrier materials are primarily aluminum metallized coated polymer films. Transparent barrier coatings provide the same oxygen and moisture barrier but have no opacity, which allows consumers to see the products while they are buying them and thus may have some selling advantages. Holographic security labels are the most widely known security packaging application. Some of the other security applications include tamper evident coatings, a whole range of radiofrequency identification labels (RFID), holographic tear tapes, customs and tax stamps, and various color shifting or optical variable devices.

Troubleshooting relative to coextrusion deals only with coextrusion problems and more specifically with problems associated with feedblocks and dies. Various coextrusion problems are covered individually with potential causes and corrective actions to implement to eliminate the problem.

Coating wires and cables with a polymer is accomplished via a crosshead extrusion process. The wire or cable to be coated is pulled at a constant rate through a crosshead die, where molten plastic covers it. Most wires and cables used in electrical and telecommunication applications and the electronics industry are coated this way.

Auxiliary equipment is defined as peripheral equipment that may be an integral part of the extrusion process to improve or optimize the extrusion process efficiency and ease of operation. It is not necessary to make the extrusion operation functional, but if properly designed and used, it can improve both the accuracy and precision of the operation.

Safety is each employee's responsibility, ranging from the janitorial staff to company president. It is the responsibility of each associate to work safely and assist other employees to operate safely, endeavoring to eliminate all unsafe acts that lead to accidents. Of all accidents, 96% are caused by human error, carelessness, or the attitude, “It won't happen to me.” Consequently, our personal safety plus the safety of those around us is the responsibility of each employee. It is essential to obey all work area rules and be alert for unsafe acts and conditions. Besides working safely, it is important to encourage those around you to work safely. Before a job is started, it needs to be thought through completely and determined if it can be done safely. If it cannot be done safely, do not do the job until you obtain the proper equipment or develop the proper procedure to do it safely. It is important to realize the hazards associated with each job and not take any shortcuts that might put you or your associates in the way of potential danger and serious accidents.