Coextruded multilayered polymers

Special processing forms, such as hot compacted polymers, coextruded multilayer polymers, electrospun nanofibers, and polymer foams... 

Michler, G.H., Balt i-Calleja, F.J., Nano- and Micromechanics of Polymers Structure Modification and Improvements of Properties (2012) Carl Hanser Verlag, Munich, Section 11.3, Coextruded Multilayered Polymers, pp. 451-477... 

Viscoelastic flow effects in polymer coextrusion. In this example we will present work done by Dooley [7, 8] on the viscoelastic flow in multilayer polymer extrusion. Dooley performed extensive experimental work where he coextruded multilayer systems through various non-circular dies such as the teardrop channel presented in Fig. 9.39. For the specific example shown, 165 layers were coextruded through a feedblock to form a single multiple-layer structure inside the channel. 

P. G. de Gennes, Physics of Polymer Surfaces and Interfaces, edited by Isaac C. Sanchez (Butterworth-Heinemann, Burlington, MA (1992), Chap. 3, pp. 55-71 J. L. Goveas and G. H. Fredrickson (1992), Apparent slip at a polymer-polymer interface, Eur. Phys. J. B2,79-92 (1998) R. Zhao and C. W. Macosko, Slip at polymer-polymer interfaces Rheological measurements on coextruded multilayers, J. Rheol. 46, 145-67 (2002). 

Zhao, R., Macosko, C. W., Shp at Polymer-Polymer Interfaces Rheological Measurements on Coextruded Multilayers, 7. Rheo. 46, 1, 2002, 145-167. 

Zhao Rui, and Macosko Christopher. Slip at polymer-polymer interfaces Rheological measurements on coextruded multilayers. J. Rheol. 46 no. 1 (2002) 145-167. 

In any polymer blend system, the nature and thickness of the polymer interface ean have a significant influence on the overall performance of the blend. AFM in tapping mode (TMAFM) was employed to establish a systematie methodology to quantitatively measure the relative interface thiekness in coextruded multilayer films. 

Company Technology This is about whether the product utilizes the company s multilayer technology. It has a weighting of 0.15. The optical polymer should have a high score because the coextruded film does not require much knowledge of other technologies such as adhesives, etc. 

Fig. 12.40 Narrow angle scattering measurements of the coextruded films. [Reprinted by permission from H. Mavridis and R. N. Shroff, Multilayer Extrusion Experiments and Computer Simulation, Polym. Eng. Sci., 34, 559 (1994).]...

Modified processing techniques have been useful for thermoplastic starch polymers. Recent work [45, 46] has examined the use of coextruded sheet processing to produce polyester / thermoplastic wheat starch / polyester multilayer films. They found that adhesion strength between the layers and stability of the interface were crucial properties in controlling the final performance properties of the films. Work by Sousa [47] has examined use of the novel shear controlled orientation injection molding (SCORIM) process to control morpholoiges and provide tensile property increases of thermoplastic starch/synthetic blends. 

Multilayer structures are often used in packaging in order to take advantage of the properties of several polymers at once. Multilayer structures are made by lamination, coating, and/or coextrusion. Because of the multiple handling of materials and the thickness of the layers, laminations (see Chapter 8) may be relatively expensive materials. Coextrusion can be used to reduce the cost of multilayer plastic film and sheet. Coextruded packaging materials are multilayer plastic sheet or film constructions produced from more than one plastic resin in a single step, using either the cast or blown film process. In coextrusion, the materials never exist as separate webs. 

Film Applications Kraton polymers blended with polypropylene and coextruded with ethylene vinyl acetate to form multilayer structures are suitable for food-wrap applications and can offer an excellent... 

The orientation in PLLA films depends on the draw rate, temperature, and ratio. High strain rate, low temperature, and high stretch ratio favor strain-induced crystallization during orientation. PLA has excellent optical properties and high modulus. However, it has low elongation, tear, and burst strengths. To overcome these shortcomings, PLA is often coextruded with other polymers to form multilayer structures to enhance its properties [27]. 

In order to tap the commercial applications of LCP in packaging, processing must achieve efficient use of the high-performance polymer. There are many high value polymers and other materials that are used in thin layers. A prime example is ethylene vinyl alcohol (EVOH), a super barrier material used as a thin layer in coextruded film and multilayer containers such as ketchup bottles. Other examples are coatings, such as metal, glass, and polymeric coatings. LCP used in thin multilayer constructions should compete well with these other materials. 

Once the coextruded LCP-thermoplastic multilayer parison is formed, it can be blow molded into bottles and other containers. The orientation in the LCP layer is controlled by the counter-rotating action of the cylinders in the die, and the LCP orientation remains in the finished bottle because of the very long relaxation time of LCP. While other polymers being coextruded with LCP may... 

Formed multilayer barrier packages, eg, trays, bowls, and cans from coextruded PP/PVDC/ PP, are being developed for soups and entrees that can be stored at ambient temperatures and heated to serving temperature in a microwave oven. Coextrusions of high performance, high temperature polymers, such as polyether-imide and polysulfone, for dual-oven containers capable of withstanding conventional bake-oven temperatures of 204-232°C are being tested. 

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