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What is a Polymer? Thermoplastics are just one class of a much larger category of materials polymers. Some familiar examples of the vast variety of products, both natural and man-made, that are composed of polymers are paper cellulose, a natural…
Dry Coloring This technique is the most widely used and is successful for the majority of blow-molded parts. Housewares and toys can be handled entirely in this manner and in the container field only the specialty high pigment items require…
Overcoming Design Limitations The necessity for, and the problems in obtaining, uniform wall thickness in blow molding part causes the molder to consider many special techniques. Some of the concepts to be reviewed in this section are production realities while…
COMPRESSION MOLDING History History has failed to establish definitely the date of origin of the art of molding. It might be said that the art of molding originated with prehistoric man when he learned how to form pottery from clay,…
SELECTION AND DESIGN CRITERIA The selection of the appropriate flow-control arrangement is the first step in the design. Ring reservoirs are then incorporated in the flow path to minimize the effects of any unbalanced flow in the feed region. The…
BLOWN-FILM DIES AND TOOLING The basic die used in making blown film is a tubing die that produces a thin wall tube. After the thin-wall tube is extruded, it is inflated by air pressure to form a large-diameter bubble of…
Fig. 1 illustrates a die equipped with a choke bar assembly used to compensate for flow variations that may exist across the width of the die. The final adjustment for extruded sheet thickness is made with the “die blade adjustment screws，’…
SHEET-DIE DESIGN Sheet plastics are made in thicknesses ranging from 0.010 in. to 1.0 in. or more, and in widths of 120 in. or more. The die orifice is a slit of the appropriate height and width (plastic sheet is…
Analytical relationships for flow rates versus pressure, which apply to the flow of plastics materials, are shown in Table 10.1. However, this table is a strict application to Newtonian fluids, where the resistance to flow is independent of the shear…
GENERAL CONCEPTS OF DIE DESIGN An extrusion die is a shaped orifice made in a block of steel or other suitable structural material that is wear- and corrosion-resistant. The function of the die is to receive the melt stream emerging…
