THESIS
2021
1 online resource (xx, 136 pages) : illustrations (some color)
Abstract
Polymer material has been recognized to take a vital role in separation processes. With the
advent of commercial interests and activities in membrane separation, a tremendous amount of
studies has been carried out on various polymer materials to investigate the polymeric structure-property
relationship for high-performance separation. However, several limits still exist for
these polymer membranes, especially the trade-off between permeability and selectivity. One
of the specialty polymers receiving great attention in the past decade is Ultrahigh Molecular
Weight Polyethylene (UHMWPE), primarily owing to its high-specific tensile properties, high
toughness and chemical inertness. Nevertheless, current processing methods for manufacturing
UHMWPE membranes remain two major problems, inclu...[
Read more ]
Polymer material has been recognized to take a vital role in separation processes. With the
advent of commercial interests and activities in membrane separation, a tremendous amount of
studies has been carried out on various polymer materials to investigate the polymeric structure-property
relationship for high-performance separation. However, several limits still exist for
these polymer membranes, especially the trade-off between permeability and selectivity. One
of the specialty polymers receiving great attention in the past decade is Ultrahigh Molecular
Weight Polyethylene (UHMWPE), primarily owing to its high-specific tensile properties, high
toughness and chemical inertness. Nevertheless, current processing methods for manufacturing
UHMWPE membranes remain two major problems, including the loss of mechanical strength
and thick membrane thickness. This thesis used the low entanglements UHMWPE gel film and
biaxially stretching method to develop super-strong thin membranes for desalination and air
filtration. These successfully synthesized materials show significant impacts as follows:
1. The UHMWPE membranes fabricated for membrane distillation (MD) desalination
exhibited an extraordinary high freshwater flux that was 2 times higher than the state-of-the-art
MD membranes in research and an excellent salt rejection of higher than 99.95 %. In addition,
the UHMWPE membrane had the capability to tackle high concentration brine water (> 15
wt.%), which was 3 times higher than the traditional reverse osmosis membrane.
2. The UHMWPE filter fabricated for air filtration is a 20 nm-thick monolayer nanofilm. It was
composed of a highly interconnected triangular pore structure with a pore size of ~ 300 nm.
The thinnest filter ribbon (fiber) only has a diameter of 7 nm, allowing the air molecules to
permeate with minimized resistance called the slip effect. Therefore, the UHMWPE filter can
reusably achieve a HEPA level filtration efficiency (> 99.97 %) with remarkably low airflow
resistance ~ 70 Pa and high transparency. While, in comparison, the opaque single-use glass
fiber HEPA filter had an airflow resistance larger than 250 Pa.
Post a Comment