PLA showed contact angle values of 72.5±2.5◦
at initial time which is consistent with those found in literature.
In general, both type of composites, PLA with Kraft lignin and PLA
with acetylated Kraft lignin, presented higher contact angle values,
obtaining a slight improvement in hydrophobic character of PLA.
Contact angle measurements demonstrate that most of the composites
containing acetylated Kraft lignin have higher contact angle
than composite with unmodified Kraft lignin. It can be observed
that to the 5% of both lignins the contact angle increased, especially
in composites with acetylated Kraft lignin. However, at more
high concentrations (10–20%) begins to decrease, being in any case
always more hydrophobic composite elaborated by PLA and AKL.
This may be due to increased roughness of the samples.