J.S. Hsieh’s scientific contributions

This study involves an investigation of the impact of the various levels of atmospheric dielectricbarrier discharge (DBD) treatment on the surface of eucalyptus fibers at different levels of beating with the objective of enhancing paper strength properties. The DBD treatment led to significant improvements in wet-strength tensile properties, increasing them by 2%-112%, as a function of the dosage of atmospheric plasma applied. Also, using controlled dosages of the DBD treatment, dry-strength tensile could be improved, reaching a 58% increase. In addition, non-beaten samples showed greater increases in strength properties than the beaten samples. Moreover, the acid surface content was unaltered by the DBD treatment, perhaps due to over-oxidation and generation of low molecular weight species that are easily removed by washing with water. Furthermore, increases in wettability could be observed for specific DBD dosage of treatments. Atomic force microscopy images of the treated handsheets showed that DBD treatment results in surface smoothing of the fibers. In conclusion, DBD treatment was shown to be an effective approach for eucalyptus fiber modification, especially in terms of enhancement of wet-strength properties.

The objective of this study was to evaluate different pretreatment methods prior to oxygen delignification on the extractive removal and selectivity improvement. Four different pretreatment methods were examined: applying ultrasonic energy, hot water soaking, soda addition with preheating, and applying mechanical shear. Acacia mangium and mixed hardwood (MHW) kraft pulps were used in this study. MHW kraft pulp did not show a significant extractive removal in all pretreatment methods during oxygen delignification. This was probably due to a low extractive content of pre-O2 MHW kraft pulp to begin with. A dramatic extractive removal occurred on the Acacia mangium pulp that was pretreated. The ultrasonic pretreatment followed by filtering induced extractive removal. Mechanical pretreatment prior to oxygen delignification promoted a better selectivity for both Acacia mangium and MHW pulps. Ultrasonic and mechanical pretreatments did not create fines formation.

The effect of mechanical pretreatment prior to oxygen delignification was investigated in this study. An Acacia mangium brownstock kraft pulp was used to evaluate the effect of oxygen delignification and mechanical pretreatment with regard to wet zero-span tensile strength (WZSTS), dry zero-span tensile strength (DZSTS) and tensile index of the pulps. A laboratory Quantum mixer was employed to perform mechanical pretreatment at 10 % consistency prior to oxygen delignification. Mechanical pretreatment followed by oxygen delignification was not found, to some extent, to affect pulp DZSTS and tensile index losses. The effect of mechanical pretreated pulp on oxygen delignification process parameters was also studied. The result was analyzed with the Yates' algorithm analysis and this showed that NaOH addition and temperature were the most detrimental to pulp WZSTS, DZSTS and tensile index losses. Kappa number was affected only by reaction temperature of oxygen delignification. This suggested that the use of NaOH addition could be reduced to compensate the mechanical pretreatment to retain the strength at certain reaction temperature of oxygen delignification. NaOH addition could be reduced as much as 51 % by applying mechanical pretreatment to obtain the same level of selectivity at the oxygen delignification conditions as described in this experiment.