LLDPE-based mono- and multilayer blown films: Property enhancement through coextrusion

In this study we investigated the performance of multi-layer coextruded linear low-density polyethylene (LL-DPE) blown films. Five-layer films were compared with monolayer dry-blended films, and the effects of layer composition and layout on the end-use properties of the coextruded films were highlighted. Three different LL-DPEs were used: a conventional Ziegler-Natta LLDPE gas phase butene copolymer, an advanced Ziegler-Natta LLDPE solution octene copolymer, and a single-site LL-DPE solution octene copolymer. Numerous five-layer coextruded structures comprising the single-site resin and the other two Ziegler-Natta resins were produced. The coextruded structures composed of the LLDPE butene and the single-site resin yielded improved end-use properties relative to the monolayer-blended films. This result was ascribed to the presence of interfacial transcrystalline layers. Also, blends of the single-site LLDPE and the advanced Ziegler-Natta LLDPE octene resins within selected layers of coextruded films showed slightly enhanced tear resistance. Finally, it was found that haze was significantly reduced when the outside layers were composed of the single-site resin.