No abstract

Lignin is a promising candidate for blends with thermoplastic polymers. Still, this endeavour is a challenge due to poor compatibility between both components. In this article, the effect of lignin esterification on the improvement of the compatibility between hardwood Kraft lignin and high‐density polyethylene (PE‐HD) is investigated. For this purpose, lignin was esterified with acetic, propionic, and butyric anhydride; its amount in the blends varied from 10 to 40%. Light microscopic images of blends show a reduction in particle size and a more homogeneous distribution with increasing length of the ester carbon chains (C2 to C4). Modification of lignin enhances the moduli and strength characteristics of the blends. Butyrated lignin performs best, as tensile strength of blends can be retained near that of pure PE‐HD with up to 40% lignin content. An additional investigation of unmodified lignin with reduced particle size confirms that modification is the decisive factor to enhance blend properties; a sole reduction of particle size is insufficient. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44582.

Steam refi ning of non-debarked poplar wood with SO 2 impregnation prior to steaming was investigated as pretreatment for enzymatic hydrolysis. Pretreatment conditions were varied in the range of 170 ° C -220 ° C, 3 -30 min and 0.7 -2.5 % SO 2 according to a factorial design. Predicted steaming conditions for highest carbohydrate yields after enzymatic hydrolysis were at 200 ° C, 15 min, and 2.5 % SO 2 . The yield of glucose and xylose from control tests under these conditions was 43 % representing an increase of 9 % compared to results of former experiments without SO 2 impregnation. Investigations on lignin extracted from the fi bers revealed no distinct differences between pretreatment with and without SO 2 . No sulfonation occurred by the impregnation with SO 2 . Topochemical analyses of the fi bers by cellular UV microspectrophotometry (UMSP) showed an inhomogeneous lignin distribution within the S2 of fi bers after pretreatment without SO 2 and local depositions of high UV-absorbing substances in the lumina of fi bers and parenchyma cells. The lignin distribution of fi ber cell walls after pretreatment with SO 2 was more homogeneous with a preserved fi ber network and only little amounts of deposited phenolic compounds in the lumina. Therefore, it might be concluded that the expulsion of lignin hinders the enzymes in accessing the cellulose.