Blown-Film Extrusion

Although extrusion blow film moulding is an efficient process, the polymer needs to have pretty high melt strength in order to stabilize the bubble and impede its collapse and/or break. For this reason, melt strength additives are often used and moreover these additives help to improve 

Typical bottle of water made of PLA obtained by blow stretch moulding (Courtesy of Acqua Sant Anna SpA). 

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What process variables control the degree of orientation in a film manufactured via cast film extrusion and blown film extrusion ... 

Polypropylene film is found in a variety of applications. Films are thin plastic sheets with thicknesses less than 250 pm. Applications for these films include candy mappers, plastic label material, electrical capacitors (which requires very pure polymer), and fiber glass insulation backing. There are two general categories of polypropylene films unoriented and oriented. Films are manufactured through either a cast or a blown film extrusion process. Oriented films exhibit improved strength relative to unoriented films. This means that they can be... 

Film adhesives, 25 582-583. See also Monolayer blown-film extrusion Multilayer blown-film extrusion Multilayer cast-film extrusion... 

Monolayer blown-film extrusion, VDC copolymers in, 25 725, 728-729 Monolayers, self-assembled, 77 57 Monolayer self-assembled systems, 16 800 Monolignols, 27 10—11, 13, 14 Monolithic drug delivery systems, 9 11 Monomagnesium phosphate, 78 839 Monomer addition, in PVC polymerization, 25 665-666... 

Multilayer blown-film extrusion, VDC copolymers in, 25 725, 729—733 Multilayer bottles, 20 52—53 Multilayer capacitors (MLCs),... 

Figure 5.12 displays a diagram of a blown film extrusion line. 

Grob, C. and Wortberg, J., Optimizing Purging Time at Product Change in Blown Film Extrusion by Selective Modification of Process Parameters, SPE ANTEC Tech. Papers, 50, 261 (2004)... 

S.S. Cherukupalli and A.A. Ogale, Online measurements of crystaUinity using Raman spectroscopy during blown film extrusion of a linear low-density polyethylene, Polym. Eng. Sci, 44, 1484—1490 (2004). 

Flexible film applications are much more demanding regarding the stiffness/ toughness ratio of the Ecoflex /PLA compound. Usually, polypropylene with a stiffness of 1,600 MPa is the stiffest product to be used in blown film extrusion. But,... 

Thermoplasticity. High molecular weight poly(ethylene oxide) can be molded, extruded, or calendered by means of conventional thermoplastic processing equipment (13). Films of poly (ethylene oxide) can be produced by the blown-film extrusion process and, in addition to complete water solubility, have the typical physical properties shown in Table 3. Films of poly(ethylene oxide) tend to orient under stress, resulting in high strength in the draw direction. The physical properties, melting behavior, and crystallinity of drawn films have been studied by several researchers (14—17). 

In blown film extrusion, the molten polymer enters a ring-shaped die either through the bottom or from the side. It is then forced around a mandrel inside llie die, shaped into a sleeve, and extruded through llie die opening in the form of a comparatively thick-walled tube. 

C. D. Han and J. Y. Park, Studies on Blown Film Extrusion, III. Bubble Instability. Analysis of the Deformation and Heat Transfer Process, J. Appl. Polym. Sci., 19, 3291 (1975). 

THV Fluoroplastic can be processed by virtually any method used generally for thermoplastics, including extrusion, coextrusion, tandem extrusion, blown film extrusion, blow molding, injection molding, vacuum forming, and as skived film and solvent casting (only THV-220). 

Plastic Suppliers Inc., a US extruder of blown film for labels and envelopes, has produced the world s first blown film from NatureWorks PLA. It was hitherto thought that PLA was unsuitable for blown film extrusion. Plastic Supplies claims that its EarthFirst film is 100% compostable, has high gloss, optimum clarity and transparency, high moisture vapour transmission rate, flavour retention, odour barrier, is breathable and is US Food and Drug Administration (FDA) compliant. Areas of application for EarthFirst include window carton film for food packaging, label film, floral wrap film, shrink film and envelope film. 

Blown film extrusion is perhaps the most widely used extrusion technique, by production volume. Billions of pounds of polyethylene are processed annually by this method to make products such as grocery sacks and trash can liners. In a blown film system (Figure 14-30), the melt is generally extruded vertically upward through an annular die. The thin tube is filled with air as it travels up to a collapsing frame that flattens it before it enters the nip rollers, which pull the film away from the die. The flattened tube then travels over a series of idle rollers to a slitter,... 

Figure I (a) Blown film extrusion, (b) Linear, two-stage production of biaxially-oritented PP...

With the flexibility of the blown film extrusion process, one-step production of wide multilayer films is possible. Incorporating a built-in adhesive layer, PVDF films can be laminated directly onto various thermo and thermoset plastics or primed metal substrates. PVDF films can protect the esthetics of UV sensitive substrates while also providing a thermal, chemical, and abrasion-resistant barrier. Recently, white PVDF films have been commercialized that are of full opacity in the UV range of 290 00 Most recently,... 

Extrusion is a cost effective manufacturing process. Extrusion is popularly used in large scale production of food, plastics and composite materials. Most widely used thermoplastics are processed by extrusion method. Many biopolymers and their composite materials with petroleum-based polymers can also be extruded. These include pectin/starch/poly(vinyl alcohol) (Fishman et al. 2004), poly(lactic acid)/sugar beet pulp (Liu et al. 2005c), and starch/poly(hydroxyl ester ether) (Otey et al. 1980), etc. In this study, composite films of pectin, soybean flour protein and an edible synthetic hydrocolloid, poly(ethylene oxide), were extruded using a twin-screw extruder, palletized and then processed into films by compression molding process or blown film extrusion. The films were analyzed for mechanical and structural properties, as well as antimicrobial activity. 

LDPE. [Dow] LDPE for blown film extrusion, coatings, inj. molding. 

Nipolon. [Tosoh] Polyethylene resins used for blow molding, blown film, extrusion pipe, extrusion coadng and laminating, inj. molding, filament... 

Primacor. [Dow] Adhesive copolymers for blown film, extrusion coatings, adhesive extrusion laminates for flexible pkg. structures, coatings, inks, adhesives. 

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