Coextruded multilayer

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. 

Coextruding Multilayer Blown Film, Dow Chemical Co., 1970s. 

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). 

Other applications include sterilizable nylon moldings in medicine and pharmacy, nylon hair combs, and nylon film for packaging foodstuffs (a typical example being milk pouches made of coextruded multilayered films of LDPE/LLDP/nylon-6, with nylon-6 as the barrier layer) and pharmaceutical products. The value of nylon in these latter applications is due to its low odor transmission and the boil-in-the-bag feature. Nylons have reasonable heat resistance. Spatula blades and spoons of nylon-6,6 withstand highest cooking temperatures. 

Bee02] Beeaff DR, Hilmas GE (2002) Rheological behavior of coextruded multilayer architectures. J Mater Sci vol 37 No 6 pp 1259-1264... 

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

The die shown in Figure 11.11 can be used to coextrude multilayer films with oriented LCP layers. 

Uniform and thin LCP layers are produced, resulting in cost-effective use of high-performance LCP resins. Coextruded multilayers may contain small fractions of high barrier LCP with impressive barrier properties at competitive cost compared to EVOH and PVDC multilayers. 

Multilayer coextrusion of thermoplastic film and sheet has developed into an important plastic fabrication process, providing large growth opportunities for the plastics industry. Coextruded multilayer plastics are challenging such traditional materials as metals, glass, paper, and textiles. 

Fig. 3. The principle of the feedblock for coextruding multilayer film or sheet. Number of layers is equal to number of feedports.

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

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... 

Coextruded multilayer PC/PMMA (50%/50%) sheet, eight layers [5, 6] ... 

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