Breathable polymer films produced by the microlayer coextrusion process

Abstract

Fabrication of a breathable film by the microlayer coextrusion process is described. Poly(ethylene oxide) (PEO) was microlayered with a filled polyolefin, either CaCO3‐filled polyethylene or CaCO3‐filled polypropylene. The thickness of individual layers was varied by increasing the total number of layers in the microlayered film from 8 to 4096. The water vapor transport rate (WVTR) was measured for microlayer films that varied in composition and number of layers. Especially with the PP(CaCO3)/PEO system, systematic variation in composition and number of layers made it possible to obtain large changes in the WVTR. The results were related to the tortuousity of the pathway through the microlayer. The filled polyolefins acted as a barrier to water vapor transport through the hydrophilic PEO. As the individual layers were made thinner by increasing the total number of layers, the polyolefin layers changed from continuous to discontinuous. Tortuousity concepts were used to correlate the increase in WVTR with an effective aspect ratio of the discontinuous polyolefin layers. In addition to high WVTR values, the breathable films produced by microlayering PEO with a filled polyolefin exhibited excellent mechanical properties. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 816–828, 2000

Probing Nanoscale Polymer Interactions by Forced‐Assembly

“…[11,12] Polycarbonate (PC, M w ¼ 62 kg mol À1 ) and poly(methyl methacrylate) (PMMA, M w ¼ 132 kg mol À1 ) are believed to be immiscible although good adhesion of the pair suggests some level of compatibility. [13,14] Coextruded films of PC and PMMA with different layer thickness were obtained by increasing the number of alternating PC and PMMA layers from 8 to 4 096.…”

“…[10] Each layer can be less than 10 nm in thickness. [11,12] Although the amount of material in a single interphase between two polymer layers is very small, the layer thickness can be made comparable to the interphase dimension, and the properties of the interphase are multiplied a thousand-fold by the number of identical interphases in the assembly. This enables us to use conventional methods of polymer analysis to probe size-scale-dependent properties as nanolayers became thinner and more interphase-like.…”

Rheology of poly(n‐butyl methacrylate) and its composites with calcium carbonate

“…6,7 Also, LLDPE/CaCO 3 or PP/CaCO 3 breathable film can be prepared, in which CaCO 3 particles create pathways for water or vapor transport through the polyolefin layers. 8,9 On the other hand, to obtain correct mechanical properties, it is necessary to have high interfacial ad-hesion. To improve the adhesion, treatment of the filler with coupling agents or reactive surface modifiers is generally employed.…”

Bio-inspired polymer optics

“…This technique produces a film with thousands of alternating layers of the two polymers; 7 the individual layer thickness can be less than 10 nm. 8,9 Because the layers are sufficiently thin, the material behaves as an effective medium. It is transparent and the refractive index can be varied smoothly between those of the constituent materials 10 by controlling the relative thickness of the layers.…”