Incorporation of nano lignin reverse micelles on the transparency, UV-blocking and rheological properties of high-density polyethylene films

Aiming to improve the poor miscibility between lignin and non-polar materials, alkali lignin (AL) was self-assembled into lignin reverse micelles (LRM) and blended with high-density polyethylene (HDPE) to fabricate composite films. The particle size of AL increased from 3.5 nm to 130 nm after forming LRM, showing a uniform spherical morphology. The water droplet contact angle increased from 54° to 89°. Optimal and rheological analysis revealed that composite films exhibited good transparency, ultraviolet (UV)-blocking performance and low viscoelasticity after adding the nano LRM. Under the optimal dosage of 5 wt% LRM, the composite film can screen 93% UV rays, and the apparent viscosities, complex viscosities, storage and loss modulus of the mixture were the lowest. Atomic force microscopy (AFM) was used to investigate the molecular interactions between lignin and HDPE. The average adhesion force between LRM and HDPE in dry air was 1.07 mN m −1 , while that between AL and HDPE was 0.77 mN m −1 . AFM experiments fundamentally demonstrated better compatibility between LRM and HDPE, which was beneficial for the improvement of UV-blocking, rheological properties, as well as their processability of LRM/HDPE films.