Performance of UV weathered HDPE composites containing hull fiber from DDGS and corn grain

The availability of distiller's dried grain with solubles (DDGS), the main co-product of corn ethanol production, exceeds its demand as feedstuff. A physical separation process named elusieve can separate the hull fiber from DDGS or corn flour to obtain DDGS with enhanced protein and oil content, or corn flour with higher starch content. This study was performed to investigate the potential of using the hull fiber separated with elusieve process on DDGS or corn flour as fillers in high density polyethylene (HDPE) composites at the commercial scale. Additionally, the degradation effects of UV accelerated weathering on this material were investigated. Commercial scale composite samples were made with six combinations of oak fiber, corn hull fiber and DDGS fiber, with the fiber loading maintained at 50%, and then the samples were subjected to UV accelerated weathering for 2000 h. The unexposed DDGS samples showed better resistance to moisture absorption (less than 5%) than the corn filler samples (18%). The specific gravity for all the filler composites was more than one for both unexposed and UV weathered composites. The DDGS fiber also showed higher flexural properties in oak25/DDGS25 than other filler composites. For all samples, the accelerated weathering resulted in a lightening during the first 1000 h of exposure, followed by a darkening at 2000 h of UV exposure. Overall, UV weathering resulted in a chain scission of the HDPE polymer increasing the crystallinity of the polymer in the weathered filler composites.