Research Articles

The wet strength of paper is an important property in its various applications. In this paper, chitosan was employed as an additive to improve the wet strength of paper using a dipping process, and maleic anhydride (MA) was used to improve the retention of chitosan. The underlying mechanism was the bridging effect of MA, via the formation of esters between MA and cellulose and amides between MA and chitosan, both of which were supported by the FT-IR results. The temporary and permanent wet strengths of the paper increased significantly, and the key parameters were 1) the concentration of MA and chitosan, 2) dipping duration, and 3) curing temperature. The temporary and permanent wet strengths reached 31.6% and 29.7%, respectively, at a concentration of treating solution of 1%, dipping time of 12 h, and curing temperature of 90 °C. At a curing temperature of 170 °C under otherwise the same conditions, both the temporary and permanent wet strengths were higher than 50%.

An alkylketene dimer (AKD) emulsion was prepared using a neotype polymeric emulsifier. The water resistance, surface tension, stability, grain diameter, and contact angle of the obtained AKD emulsion were investigated under different conditions, such as emulsification temperature, emulsification time, solids content, and amount of emulsifier. The experimental results demonstrated that the sizing effect of the AKD emulsion was fairly good under the following conditions: emulsification temperature, 75°C; emulsification time, 9 min; solids content, 10%; and the amount of emulsifier, 3%.

Foam technology enables the preparation of new fiber-based materials with reduced density and improved mechanical performances. By utilizing multi-scale structural features of the formed fiber network, it is possible to enhance the elasticity of lightweight cellulose materials under compressive loads. Sufficient strength is achieved by optimally combining fibers and fines of different length-scales. Elasticity is improved by adding polymers that accumulate at fiber joints, which help the network structure to recover after compression. This concept was demonstrated using natural rubber as the polymer additive. For a model network of viscose fibers and wood fines, the immediate elastic recovery after 70% compression varied from 60% to 80% from the initial thickness. This was followed by creep recovery, which reached 86% to 88% recovery within a few seconds in cross-linked samples. After 18 h, the creep recovery in those samples was almost complete at up to 97%. A similar improvement was seen for low-density materials formed with chemi-thermomechanical fibers. The formed structure and elastic properties were sensitive not only to the raw materials, but also to the elastomer stiffness and foam properties. The improved strain recovery makes the developed cellulose materials suitable for various applications, such as padding for furniture, panels, mattresses, and insulation materials.

Thermal decomposition characteristics and kinetics of high-density polyethylene (HDPE), corn stover (CS), and their blended mixture (1:1 w/w ratio) during non-catalytic and catalytic co-pyrolysis were studied via thermogravimetric analysis (TGA). The results indicated synergetic interactions between the biomass and the plastics during co-pyrolysis as measured by weight loss (ΔW); this effect was attributed to radical interactions during co-pyrolysis. The pyrolysis catalysts with higher nickel loadings (5%, 10%, and 15%) appreciably diminished the solid residue. Kinetic studies indicated that the pyrolysis was a first-order reaction based on the fitted thermogravimetric data. The activation energy (E) and pre-exponential factor (A) ranged between 26.13 kJ/mol to 392.67 kJ/mol and between 156.24 min-1 to 9.19 x 1023 min-1, respectively. There was a kinetic compensation effect (KCE) observed among the two kinetic parameters. The activation energy (E) decreased for each pyrolysis stage with the presence of a catalyst. The results indicated that catalytic co-pyrolysis could provide great potential for reducing the pyrolysis energy input.