MACHINERY | FLAT DIES
As previously mentioned, stretch film is also an
important application. Research has shown that mechanical properties of a co-extrusion can be enhanced with micro-layered film structures. One such example is the work of Mueller et al., who showed the improvement of toughness as the number of layers increased for a breathable film structure, made of CaCO3
-filled PP and PEO co-extrusion [7]
Figure 2: Enhanced Specular Reflection (ESR) films rely on nano-layering for their properties
interesting optical properties can be obtained for multilayer structures with a high number of thin layers, when controlling the thickness and the refractive index of the two alternating polymers. For instance, it is possible to tune the refractive spectrum of the film. Some films can therefore have iridescent
properties just like nacre. One large commercial application of these films is the Enhanced Specular Reflector (ESR) films used in display applications (as shown in Figure 2).
. Figure 3 (next page) shows the relatively
ordinary tensile properties for the polymers used. Just as for nacre, mechanical properties are improved when coextruding this recipe into nano-layered structures. In this case, the ultimate film made in the lab, with 4,096 layers, has an elongation at break that is better than either of the constituent polymers and equivalent ultimate strength as the filled polypropylene. While this was a lab-scale demonstration, cast
stretch film is an industrial application for commod- ity film. Here, nano-layer co-extrusion has shown benefits for film mechanical properties and been quite commercially successful. Compared to similar recipes produced as traditional 5 or 7-layer co-extrusion structures, nanolayer films have shown
PVC CLING FILM LINES
BG PLAST IMPIANTI s.r.l. Via Venezia 232 21050 Marnate - Italy Phone: +39 0331 365 865 -
info@bgplast.it
ROBEL do Brasil Ind. e Com de Máq. Ltda Rua Sisa, 11 - Cid. Ind. Sat. de SP 07221-030 GUARULHOS, SP, Brazil Phone: +55 11 2487-6900 -
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