Biomedical Engineering Reference
In-Depth Information
chemistries that allows for the separation of cellulose from lignin without mechani-
cal action; (5) development of systems that simulate the growth of cellulose in trees
or plants that can be accomplished on a industrial scale; (6) dissolution of cellulose
into ionic liquids with precipitation of cellulose into a continuous fiber or incorpo-
ration of threads or honeycomb weaves of cellulose into a variety of different mate-
rial matrixes; (7) reacting wood pulp fibers in a solvent medium that does not fully
penetrate the fibers followed by hot-pressing the partially modified pulp fibers at ele-
vated temperature to form a semi-transparent polymer sheet that is a nanocompos-
ite of cellulose esters and unmodified cellulose; (8) use of cellulose nanocrystals for
reinforcement of other matrix materials; extreme refining of cellulose fiber resulting
in increasing Canadian Standard Freeness (Roman and Winter 2006): and (9) mod-
ification of the side chains of cellulose to further enhance self assembly (Gray and
Roman 2006).
A variety of understanding and characterization techniques would need to be estab-
lished to accomplish the above. These include: (a) understanding cell wall formation
in tree and plants; (b) development of the appropriate inorganic chemistry for linking
cellulose; (c) understanding of cellulose chemistry and the sheet layering of cellulose
to establish pathways by which cellulose could be modified to enhance self assembly;
(d) understanding and modeling the formation of cellulose from glucose or other simple
sugars by bacteria; (e) understanding of the effect of a variety of enzymes on the struc-
ture and tensile strength of cellulose; (f) understanding of the chemistry of cellulose and
manipulation of its precipitation based on its solubility in various liquids and subsequent
processing; and (g) effects of enzymes and extreme refining conditions on cellulose and
cellulose composites.
Use of cellulose in a variety of different matrixes will be dependent on the interactiv-
ity of the matrix material with cellulose and lignocellulose surface chemistry. Wetting
and surface area play key roles in the formation of high-strength interfaces between the
matrix, matrix components and cellulose. Nanomaterials can provide unique levels of
surface area for the formation of chemical bridges between the cellulose, the matrix and
other fillers used. The strength of cellulose composites is influenced by the chemical
interface and cellulose particle geometry. Interfacial interactions are governed by adhe-
sion, water sorption, durability, and processing of the material. Cellulose derivatives
can also be combined with nanomaterials and used in conjunction with cellulose fibers,
or other fibers to form nanocomposites (Choi and Simonsen 2006).
1.12.5
Capturing the Photonic and Piezoelectric Properties of Lignocelluloses
Many grades of paper require using higher grammage (basis weights) than needed, not
because of strength property end use requirement but because of the need to achieve
sufficient opacity. Our target to use nanotechnology to help overcome this technical
barrier and allow lower grammage sheets to be used in printing and writing allocations
will result in paper with lower opacity and the likelihood of it not being fit for use.
While this would allow savings by permitting raw material reductions in both fiber and
coating, we need to avoid the loss of optical performance of the paper by building
'optical band gap' coatings to enhance opacity. Nanotechnology could also provide the
ability to produce high sheet brightness with no fluorescence and could eliminate the
Search WWH ::




Custom Search