Blow molding multilayer

Coextrusion Blow Molding Most of the Above Tips Also Apply to Blow Molding Multilayer Containers. ... 

Blow molded multilayer plastic Polyolefins France 2,132,395 1972 Mitsui Petrochemical... 

Laminar materials are produced by a variety of techniques. Coextrusion blow-molding produces a number of common food containers that consist of multilayers such as layers consisting of PP-adhesive-PVA-adhesive-adhesive-PP. 

Multilayered articles can be made by coinjection blow-molding or coextrusion methods. A three-layer system generally contains a barrier layer sandwiched between two exterior layers. These are actually laminar products. In the coextrusion sequence, several extruders can be used to place the material into the mold. The multilayer container is then produced from blowing air into the preform. 

The multilayer film is formed by injection molding, co-injection blow molding, co-injection stretch-blow molding or co-extrusion blow molding techniques. 

Extrusion. Sheet, film, and profiled articles are made by extrusion (20). The resin is melted and forced through a die plate or head. Variations include multilayer and blown film applications. In multilayer coextrusions, different combinations of plastics are separately but concurrently extruded to form layered sheet or film. In the packaging industry, specialty resins such as high barrier ethylene—vinyl alcohol copolymers are combined with heat- and impact-resistant thermoplastics for food packages. The properties of each resin layer are additive, as opposed to the "averaging of property" in blends. Multilayers are also used for blow-molded containers, films, and sheet products (see also Film AND sheeting materials). 

As we will see in Chapter 9, multilayer blow molding is sometimes used as a way to incorporate recycled polymer in food-grade bottles. For safety reasons the use of recycled plastics in packaging that comes in direct contact... 

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... 

Keener, C. et al., Optimizing Extrusion Blow Molding for Multilayer Container Production, Graham Machinery Group, York, PA, Aug. 15, 2001. 

BLOW-MOLDED CONTAINERS. Initial evaluation of SELAR OH Plus in extruded blow molding containers was disappointing. Barrier improvements of only 30 to 401 were measured compared to the expected 300%.. The resolution of this discrepancy provided some valuable insights into the role of platelet orientation in barrier improvement and the effects of die swell in multilayer extrusion blow molding. 

The best way for the reader to learn is to study actual examples of parts made by the blow molding of fluoropolymers. A majority of such parts have a multilayer construction to combine the properties of other plastics in a composite structure. The most common technique for producing multilayer sheet/film is coextrusion. The chemical resistance of fluoropolymers makes them attractive materials for inner layers of containers that come in contact with aggressive chemicals that can swell or degrade thermoplastics. 

Technology to successfully produce multilayer injection blow molded bottles is much newer than that to produce multilayer extrusion blow molded bottles. Heinz Inc. s ketchup bottle was the first U.S. example (Fig. 12.22). The use of PET bottles made by coinjection blow molding has grown rapidly. As is the case for coextrusion blow molding, the key is production of the parison. Once the multilayer parison is produced, the remainder of the process is essentially the same as for single layer materials. Even stretch blow molding can be used. 

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