Doctoral Dissertations

Date of Award

8-2004

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Materials Science and Engineering

Major Professor

Dong Zhang

Committee Members

Christine (Qin) Sun, Larry C. Wadsworth, Randall R. Bresee, Gajanan S. Bhat, Kevin M. Kit

Abstract

Finer fibers are increasingly desirable in the nonwoven industry in many applications due to increased specific surface area, increased surface adsorption ability, and improved filtration efficiency. Splitting bicomponent (Bico) fibers to produce finer fibrous nonwoven webs has become one of the hot topics in nonwoven industries.

Investigation of Bico fiber splitting mechanism and hence finding proper ways to achieve fiber splitting in S/S Bico MB nonwoven webs are the key issues in this research. Based on the fiber splitting mechanism, incompatible polymer pairs were chosen and appropriate post-treating methods as well as the post-treating agents were selected to facilitate fiber splitting in S/S Bico MB nonwoven webs.

Several post treatments were used to split side-by-side meltblown nonwoven fibers in this research, including hydroentanglement, heat-stretching, NaOH and benzoic acid treatment. In each post treatment method, fiber splitting was examined with SEM and/or laser-source microscope. Fiber diameter, web structure and web properties were examined before and after the fiber splitting inducing treatment.

Hydoentanglement has been applied to S/S Bico MB nonwoven webs with Bico pairs of PA6/PE. PA6/PP and PA6/PET. Fiber diameter, web structure and webproperties were examined based on the corresponding test standards. Fiber splitting phenomenon and web morphology were observed with SEM, and web structure was evaluated using WebPro technology.

Heat-stretching post treatment was applied to S/S Bico MB nonwoven webs with Bico pairs of PA6/PE and PA6/PP. The fiber splitting phenomenon was observed using SEM; fiber diameter and web properties in MD and CD were examined, especially the change in flexural rigidity and elasticity of the heat-stretched webs.

The S/S Bico MB nonwoven webs of 25PE/75PET, and 50PBT/50PP were treated with sodium hydroxide at a bath ratio of 1/20 and temperature of 100C using different concentrations of NaOH at different treating times. The fiber splitting phenomenon was investigated using SEM in this research.

Benzoic acid (BA) has been employed to split S/S Bico MB webs composed of 50PET/50PA6 and 50PP/50PA6. The degree of fiber splitting was evaluated using both fiber splitting ratio and initial dye adsorption ration (initial dyeing ration) in this research. Web properties were examined to characterize the change after benzoic acid treatment. The fiber splitting mechanism during BA treatment was discussed as well, and it was concluded that the BA method could be an efficient way to split S/S Bico MB fibers, compared to the foresaid three methods.

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