Abstract
To develop functional and sustainable products from
future wood biorefineries, birch kraft pulp xylan was
alkali-extracted and modified in aqueous solvent with
hydroxypropylation to enhance its processability to
films. For the first time, the roles of internal vs.
external plasticization in the mechanical, thermal, and
barrier performance of xylan films were systematically
evaluated as a function of the degree of substitution
(DS) of hydroxypropyl (HP) groups (internal plasticizer)
and the added sorbitol (external plasticizer). In
addition, the moisture uptake and the degree of
crystallinity of hydroxypropyl xylan (HPX) films were
characterized. Internal plasticization of xylan with HP
groups enabled cohesive film formation, but did not form
barrier materials alone. The addition of sorbitol as
external plasticizer was necessary to obtain gas barrier
films. The combinations of internal and external
plasticization at selected ratios enabled the tailoring
of film properties. Low to medium DS of HP and the
addition of 10% or 20% sorbitol resulted in promising
barrier properties. The tensile strength of the HPX films
was rather high between 27 and 43 MPa, depending on the
level and type of plasticization. The thermal stability
of HPXs increased and the degree of crystallinity of
xylan in the films decreased as the internal
plasticization increased. The glass transition
temperature of HPXs and HPX films decreased more with
external than with internal plasticization. The studied
concept would benefit the sustainable exploitation of
natural resources. The promising material properties,
high degree of biobased raw materials, and non-food
origin make HPX-based films an interesting option for
multilayer paperboard coating for food packaging, for
example.
Original language | English |
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Pages (from-to) | 307-318 |
Journal | European Polymer Journal |
Volume | 66 |
Issue number | May |
DOIs | |
Publication status | Published - 2015 |
MoE publication type | A1 Journal article-refereed |
Keywords
- barrier properties
- films
- hydroxypropyl xylan
- materials
- polysaccharides