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Multiple layers are formed by coextrusion, lamination, or various coating technologies. The material of construction of multilayered packaging ranges from paper to plastics to metals. Most multilayered packages are not readily recyclable. [2] Basf company and Uflex recently developed multilayered food packaging from 100% recyclable materials ...
Before drawing, polymer melt is pushed through a die with a large number of small holes, known as a spinneret. Typically, the fibers are air cooled without any need for curing. If curing is needed, two methods are available: dry and wet spinning. In wet spinning, the polymer is dissolved and extruded through a spinneret into a chemical bath.
Coextrusion is the extrusion of multiple layers of material simultaneously. This type of extrusion utilizes two or more extruders to melt and deliver a steady volumetric throughput of different viscous plastics to a single extrusion head (die) which will extrude the materials in the desired form.
The thickness of the resulting wet coated layer is controlled by tuning the ratio between the applied volumetric pump rate and areal coating rate. Unlike in self-metered coating methods such as blade- and bar coating, the slot-die does not influence the thickness of the wet coated layer via any form of destructive physical contact or scraping.
A variant of wet spinning is dry-jet wet spinning, where the spinning solution passes through an air-gap prior to being submerged into the coagulation bath. This method is used in Lyocell spinning of dissolved cellulose, and can lead to higher polymer orientation due to the higher stretchability of the spinning solution versus the precipitated ...
Diagram of bar drawing; the workpiece is pulled from left (tension) rather than pushed from the right (compression). Drawing is a manufacturing process that uses tensile forces to elongate metal, glass, or plastic. As the material is drawn (pulled), it stretches and becomes thinner, achieving a desired shape and thickness.
For example, juiceboxes are fabricated from liquid packaging board which is usually six layers of paper, polyethylene, and aluminum foil. Paper is used in the lamination to shape the product and give the juicebox an extra source of strength. The base is most often particle- or fiberboards, then some layers of absorbent kraft paper.
Extrusion coating is the coating of a molten web of synthetic resin onto a substrate material. It is a versatile coating technique used for the economic application of various plastics , notably polyethylene , onto paperboard , corrugated fiberboard , paper , aluminium foils , cellulose , non-wovens , or plastic films .