Kaustubh Joshi

Kaustubh was awarded his Masters by Research thesis on the 21st of June 2007.

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Chapter 2 reviews the literature and the studies carried out so far in the pursuit of measuring shear bond strength. It also discusses the difficulties in measuring shear bond strength and the various pros and cons of the previously devised methods.

Chapter 3 presents the new experimental methods designed in the studies for this thesis and explains the idea behind the design. It also describes the various steps in designing the new experiments and the equipment used. Isotropic handsheets with proper grammages and thickness control were prepared and acid (HCl) exposed to weaken the fibres in the sheet of paper to such an extent that the fibre strength equaled the bond strength of a single fibre-fibre bond. Uniform acid exposure and an arrangement to rapidly remove the acid vapours from the vicinity of the sheet were needed to stop the reaction between the acid and the paper. A new rig was designed for this purpose. Optimum exposure was determined by observing the tensile test fracture line with the help of confocal laser scanning microscopy after different levels of acid exposure. Zero span tensile strengths were used to determine the fibre strength. Fibre width has been measured using the confocal microscopy and image analysis software.

Chapter 4 presents the results generated in the course of the experiments and goes on to discuss the relevance of the results and what how they are used to measure the shear bond strength. The calculated values of the shear bond strength are presented in this chapter: Never dried (29.6 ± 3.3 MPa), once dried (24.7 ± 2.8 MPa) and high temperature dried (19.7 ± 2.2 MPa) Radiata pine pulp, 60% yield.

Chapter 5 presents the conclusions of the studies and recommendations for future work. Bond strength values show that fibres tend to lose shear bond strength after drying and the loss of shear bond strength is much more if the fibres are undergoing a heat treatment for drying. This may be due to the Hornification. Further investigations are needed to determine the cause of shear bond strength  loss and the mechanisms by which it would be possible to reverse the strength loss. A new method to measure the shear bond strength of paper has been established. The bond strength accounts for paper as a network instead of single fibre measurements. The new measurement procedure is also much quicker than previously published procedures.

This thesis is a part of the ongoing studies in the field of paper science and could be used as an input in developing the complete model describing paper mechanical properties.