Fabrication processes film blowing

EVOH have superior gas barrier properties.80 89 They are often used as the internal layer in multilayer food packaging films, blow molded rigid containers, gasoline tanks for automobiles for a variety of purposes, etc. EVOH can be fabricated by the usual melt processing methods. The barrier properties of films decrease in the presence of moisture, so multilayer with protective polypropylene (especially biaxially oriented material), low-density polyethylene, nylons, or other moisture barrier films provides films or products that are useful even with liquids. The... 

Polymer scientists and engineers have developed a wide variety of processes by which to convert polypropylene into useable articles. These processes include fiber-spinning, production of melt blown and spun bond non-woven fabrics, film production, blow molding, and injection molding. The following sections describe these processes and the resulting properties of the product as a function of the process. 

Polyethylene is readily fabricated by all methods of thermoplastic processing. The principal methods used are film and sheet extrusion, extrusion coating, injection molding, blow molding, pipe extrusion, wire and cable extrusion coating, rotomolding, and hot melt and powder coatings. 

The final product may take any one of a vast multitude of final forms. These include, but are not limited to, construction materials, toys, automotive parts, kitchen aids, industrial parts, sports and recreational equipment, containers of all sizes and description, and an unlimited variety of packaging products for foods, drugs, cosmetics, and other consumer products. The processes that are used to produce or mold or fabricate the final products are also varied and depend on the design and purpose of the product. Some of these processes include extrusion, compression molding, roto-molding, blow molding, sheeting, and films. 

Polyethylene is the least costly of the major synthetic polymers. It has excellent chemical resistance and can be processed in a variety of ways (blown film, pipe extrusion, blow molding, injection molding, etc.) into myriad shapes and devices. Fabrication methods will be briefly discussed in Chapter 8. 

The easy processability of the polyolefins permits ready fabrication by nearly all conventional processes. This versatility, plus their low cost, low density, and excellent balance of physical properties, gives them wide applicability in many different end-use fields. We now encounter polyolefins in our daily lives in the form of fibers (e.g., indoor-outdoor carpeting, underwear, and upholstery), film (packaging), blow-molded containers (squeeze bottles, detergent bottles), injection molded articles (housewares, appliance housings, auto parts), and extrusions (wire insulation, pipe). Statistics on major applications and accounts of new developments are published regularly (22). 

Film Processing Methods Extrusion, extrusion blow-molding, thermoforming, injection molding, fabrication, andheat-seahng.l ... 

Polyvinyl Chloride Thermoplastic polymer of vinyl chloride, available in rigid and flexible forms. Has good dimensional stability, fire resistance, and weatherability, but decreased heat and solvent resistance and high density. Processed by injection and blow-molding, calendering, extrusion, and powder coating. Used in films, fabric coatings, wire insulation, toys, bottles, and pipes. Also called PVC. 

Polymer extrusion-based processes Some of the most significant contributions to the nonwoven industry came from the development of the direct polymer-to-fabric converting processes. These processes include spun-bonding, melting-blowing, and porous film. Nonwovens made by these processes are known as spunbond (SB) nonwovens, melting blown (MB) nonwovens, and apertured-fllm nonwovens. 

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