Reinforced distiller's grains as bio-fillers in environment-friendly poly(ethylene terephthalate) composites.

Incorporating distiller's grains (DG) into poly(ethylene terephthalate) (PET) has not been investigated because DG is not suitable for processing at high temperatures. Hence, in this study, DG was treated with methylenediphenyl diisocyanate (MDI) to prepare reinforced DG (RDG), which was then used as a biological filler that was melt-mixed with a PET resin to produce PET/DG and PET/RDG composites. The composite mechanical properties were investigated. Compared with PET/DG composites, PET/RDG composites exhibited improved mechanical properties. When the RDG content was 12.5%, the elongation at break reached the maximum. Scanning electron microscopy was used to observe the structure of composites filled with MDI-modified DG at the tensile section, and the compatibility between RDG fillers and the PET matrix was analyzed; RDG dispersed and adhered well in the matrix. The FTIR results showed the appearance of new characteristic peaks, indicating the possibility of DG reacting with MDI after the blending with PET, as well as providing clues about the probable reaction mechanism. Through X-ray diffraction, thermogravimetric analysis, differential scanning calorimetry, and water absorption tests, the crystallinity, thermal stability, and water absorption for the composites were analyzed. The results of TGA showed that RDG had a higher thermal stability than DG. Adding DG could significantly increase the crystallinity and rate of crystallization of PET, and at the same time, it could also improve the water absorption performance of the composites. But in the case of DG modification or treatment with MDI, the water absorption was slightly reduced. The results of contact angle analysis showed that the surface of PET/RDG composites had higher hydrophobicity than that of PET/DG composites because of the tighter structure. Relative to DG, RDG also effected improvement in the thermal stability of PET. [ABSTRACT FROM AUTHOR]