Visible and Infrared Scattering from Melt-processed Polyethylene Fibers

摘要

Polyethylene is a commonplace polymer that nevertheless has interesting thermal and mechanical properties. Because of its minimal infrared absorption and its ability to be oriented with a potentially manufacturable stretching process, oriented polyethylene, especially oriented high- or even ultrahigh-molecular weight polyethylene (HDPE and UHMWPE, respectively), has demonstrated unusually interesting thermal properties for a polymer. The interesting properties of polyethylene films include very high thermal conductivity [1] and high broadband long-wave infrared (LWIR) transmission, except at around 14 Dm. Lozano et. al. showed that in UHWMPE films, stretched with draw ratios as much as 100x, crystallinity and homogeneity increase due to ordering of amorphous regions and alignment of crystallites [2]. The increase in homogeneity, as well as the reduction in film thickness, both due to stretching/drawing, reduces LWIR scattering and increases LWIR transmission [2]. We report research on HDPE fibers with diameters in the 20-150 Dm range, including those containing particles that scatter infrared light, in an effort to better control thermal scattering in manufacturable melt-processed fibers. While polyethylene is typically not used in worn textiles, we demonstrate a method to introduce both color and moisture vapor penetration through these thermally-functional fibers, making them potentially more interesting for textile applications. We also introduce bio-optically important materials such as cephalopod pigments enclosed in ~ 500 nm granules, for scattering and controlling visible color in these fibers, of interest for display and colorimetric measurement capabilities. Scattering measurements from individual fibers are analyzed to predict future infrared performance of these thermally-functional fibers.