Nanocrystals from recycled wood waste make carbon-fiber composites
tougher

Date:
August 11, 2020
Source:
Texas A&M University
Summary:
Researchers have used a natural plant product, called cellulose
nanocrystals, to pin and coat carbon nanotubes uniformly onto the
carbon- fiber composites. The researchers said their prescribed
method is quicker than conventional methods and also allows the
designing of carbon-fiber composites from the nanoscale.



FULL STORY ========================================================================== Polymers reinforced with ultra-fine strands of carbon fibers epitomize composite materials that are "light as a feather and strong as steel,"
earning them versatile applications across several industries. Adding
materials called carbon nanotubes can further enhance the composites' functionality. But the chemical processes used for incorporating carbon nanotube end up spreading them unevenly on the composites, limiting the strength and other useful qualities that can be ultimately achieved.


==========================================================================
In a new study, Texas A&M University researchers have used a natural
plant product, called cellulose nanocrystals, to pin and coat carbon
nanotubes uniformly onto the carbon-fiber composites. The researchers
said their prescribed method is quicker than conventional methods and
also allows the designing of carbon-fiber composites from the nanoscale.

The results of the study are published online in the journal American
Chemical Society (ACS) Applied Nano Materials.

Composites are built in layers. For example, polymer composites
are made of layers of fiber, like carbon fibers or Kevlar, and a
polymer matrix. This layered structure is the source of the composites' weakness. Any damage to the layers causes fractures, a process technically known as delamination.

To increase strength and give carbon-fiber composites other desirable qualities, such as electrical and thermal conductivity, carbon nanotubes
are often added. However, the chemical processes used for incorporating
the carbon nanotubes into these composites often cause the nanoparticles
to clump up, reducing the overall benefit of adding these particles.

"The problem with nanoparticles is similar to what happens when you add
coarse coffee powder to milk -- the powder agglomerates or sticks to
each other," said Dr. Amir Asadi, assistant professor in the Department
of Engineering Technology and Industrial Distribution. "To fully take
advantage of the carbon nanotubes, they need to be separated from each
other first, and then somehow designed to go to a particular location
within the carbon-fiber composite." To facilitate the even distribution
of carbon nanotubes, Asadi and his team turned to cellulose nanocrystals,
a compound easily obtained from recycled wood pulp. These nanocrystals
have segments on their molecules that attract water and other segments
that get repelled by water. This unique molecular structure offers the
ideal solution to construct composites at the nanoscale, said Asadi.

The hydrophobic part of the cellulose nanocrystals binds to the carbon
fibers and anchors them onto the polymer matrix. On the other hand,
the water- attractive portions of the nanocrystals help in dispersing
the carbon fibers evenly, much like how sugar, which is hydrophilic,
dissolves in water uniformly rather than clumping and settling to the
bottom of a cup.

For their experiments, the researchers used a commercially available
carbon- fiber cloth. To this cloth, they added an aqueous solution of
cellulose nanocrystals and carbon nanotubes and then applied strong
vibration to mix all of the items together. Finally, they left the
material to dry and spread resin on it to gradually form the carbon
nanotube coated polymer composite.

Upon examining a sample of the composite using electron microscopy,
Asadi and his team observed that the cellulose nanocrystals attached to
the tips of the carbon nanotubes, orienting the nanotubes in the same direction. They also found that cellulose nanocrystals increased the composite's resistance to bending by 33% and its inter-laminar strength
by 40% based on measuring the mechanical properties of the material
under extreme loading.

"In this study, we have taken the approach of designing the composites
from the nanoscale using cellulose nanocrystals. This method has allowed
us to have more control over the polymer composites' properties that
emerge at the macroscale," said Asadi. "We think that our technique
is a path forward in scaling up the processing of hybrid composites,
which will be useful for a variety of industries, including airline and automobile manufacturing."

========================================================================== Story Source: Materials provided by Texas_A&M_University. Original
written by Vandana Suresh.

Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Shadi Shariatnia, Annuatha V. Kumar, Ozge Kaynan, Amir Asadi. Hybrid
Cellulose Nanocrystal-Bonded Carbon Nanotubes/Carbon Fiber Polymer
Composites for Structural Applications. ACS Applied Nano Materials,
2020; 3 (6): 5421 DOI: 10.1021/acsanm.0c00785 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/08/200811204530.htm

--- up 3 weeks, 6 days, 1 hour, 55 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1337:3/111)