TITLE:
Use of Poly-Lactic Acid (PLA) to Enhance Properties of Paper Based on Recycled Pulp
AUTHORS:
Klaus Doelle, Anh T. Le, Thomas E. Amidon, Biljana M. Bujanovic
KEYWORDS:
Poly-Lactic Acid (PLA), Recycled Pulp (OCC), Starch, Paper Properties, Paper Handsheets
JOURNAL NAME:
Advances in Chemical Engineering and Science,
Vol.4 No.3,
July
14,
2014
ABSTRACT:
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.