Nowadays, recycled paper is broadly used due
to environmental reasons. Furthermore, the addition of starch as a dry strength
additive improves the properties of recycled paper. Poly-Lactic Acid (PLA), a
product from bio-refinery process, has recently been shown to act as a
promising strength additive that could be used in combination with starch to further
improve the strength of paper. In this study, the use of PLA of three molecular
weights (MW) in combination with four different starches was investigated.
Three recycled pulps from different origins, with the kappa number of 27.9 to
66 were used. Paper handsheets were made, and selected paper properties were
tested. The results indicate that handsheets properties were influenced by the
MW of PLAs, the type of starch used, and the lignin content of the pulp. The
paper handsheets made from lignin-rich pulp (pulp A, kappa number 66), combined
with 0.1% medium MW PLA (PLA_1) and 0.9% cationic starch containing 0.43% N
gave the highest improvement for tensile strength, wet tensile strength, air
and water resistance. This result verifies that a higher kappa number pulp has
better attraction to the hydrophobic PLA. Moreover, the higher charge cationic
starch led to higher tensile strength due to the increase of affinity to the
anionic fiber surface. Interestingly, results show that amphoteric starch is a
promising substitute for high cationic charge starch when combined with the
medium MW PLA to improve tensile strength of paper. This study demonstrated
that a starch-PLA blend represents a promising approach in improving properties
of recycled paper.
Article by Klaus
Doelle,et al,from State University of New York,USA.
Full access: http://mrw.so/2fZdVg
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| Image by Christine Cavalier,from Flickr-cc. |
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