Abstract
The beneficial effects of the addition of polylactic acid (PLA) to the strength properties of different pulps have recently been reported. In the present study, we used PLA, as a projected biorefinery product, to enhance the strength of paper test sheets made from bleached and unbleached kraft pulp produced from hot-water extracted and unextracted sugar maple. PLA surface treatment (2% addition based on OD fibers) was efficient in reinforcing paper made from all types of investigated pulps. However, the increase in tensile strength was higher for unbleached than for bleached pulps. This is probably an effect of the higher attraction between fibers rich in lignin and the relatively hydrophobic PLA. In an attempt to increase the reinforcing effect of PLA, curing of PLA-treated paper test sheets was performed at 60 degrees C. The effect of curing appeared to depend on the chemical composition of the pulp. Nevertheless, these results showed that paper made from hot-water extracted sugar maple after reinforcement with 2% PLA could be equivalent to or even greater in strength than paper made from kraft pulp produced from unextracted sugar maple, while retaining its higher bulk.