Coaxial cellulose-based aerogel fibers
The present disclosure provides a coaxial fiber comprising a cellulose fiber exterior, and a hollow interior, wherein the aerogel occupies the hollow interior of the cellulose fiber. The present disclosure also provides a method of making the coaxial fiber, and a method of maintain a temperature differential in two zones using the coaxial fibers described herein.
1 . A coaxial fiber comprising
an exterior and an interior, wherein
the coaxial fiber exterior is a cellulose fiber sheath comprising cellulose and polyacrylic acid; and
the coaxial fiber interior is a core surrounded by the cellulose fiber sheath, wherein the core comprises an aerogel.
2 . The coaxial fiber of claim 1 , wherein the cellulose fiber sheath comprises a ratio of about 90:10 to 99:1 of cellulose to polyacrylic acid.
3 . The coaxial fiber of claim 1 , wherein the cellulose fiber sheath comprises a ratio of about 92:8 of cellulose to polyacrylic acid.
4 . The coaxial fiber of claim 1 , wherein the cellulose fiber sheath comprises pores.
5 . The coaxial fiber of claim 4 , wherein the pores have a size of about 20 nm to about 40 μm.
6 . The coaxial fiber of claim 1 , wherein the aerogel comprises a cellulose nanofibril (CNF) aerogel.
7 . The coaxial fiber of claim 1 , wherein the coaxial fiber has an outer diameter of about 500 μm to about 1500 μm.
8 . The coaxial fiber of claim 1 , wherein the coaxial fiber has a porosity of at least about 85%.
9 . The coaxial fiber of claim 1 , wherein the coaxial fiber has a density of about 0.2 g/cm 3 .
10 . The coaxial fiber of claim 1 , wherein the coaxial fiber has a specific tensile strength of about 20 MPa·g/cm 3 to about 30 MPa·g/cm 3 .
11 . The coaxial fiber of claim 1 , wherein:
the cellulose fiber sheath comprises pores having a size of about 20 nm to about 40 μm;
the aerogel comprises a cellulose nanofibril (CNF) aerogel; and
the coaxial fiber has an outer diameter of about 500 μm to about 1500 μm, porosity of about 85%, a density of about 0.2 g/cm 3 , and a specific tensile strength of about 21 MPa g/cm 3 to about 26 MPa g/cm 3 .
12 . A method for preparing the coaxial fiber of claim 1 , the method comprising:
(a) wet-spinning an organic solution comprising cellulose acetate and polyacrylic acid on the exterior of a water core to form a coaxial fiber comprising an exterior and an interior, wherein the coaxial fiber exterior is a cellulose fiber sheath and the coaxial fiber interior is a core filled with water;
(b) removing the water from the core of the coaxial fiber resulting from step (a) to form a hollow core;
(c) injecting an aqueous cellulose nanofibril suspension into the hollow core of the coaxial fiber resulting from step (b); and
(d) freeze-drying the coaxial fiber resulting from step (c) to form a coaxial fiber comprising an exterior and an interior, wherein the coaxial fiber exterior is a cellulose fiber sheath and the coaxial fiber interior is a core comprising a nanofibril aerogel, thereby forming the coaxial fiber of claim 1 .
13 . The method of claim 12 , wherein the organic solution comprises dimethylacetamide.
14 . The method of claim 12 , wherein the organic solution comprises about 30:1 to about 20:5 w/w of cellulose acetate to polyacrylic acid.
15 . The method of claim 12 , wherein the organic solution comprises about 23:2 w/w of cellulose acetate to polyacrylic acid.
16 . The method of claim 15 , wherein the organic solution comprises about 16% by weight of 23:2 w/w of cellulose acetate to polyacrylic acid.
17 . The method of claim 12 , further comprising after step (a), the step of (a1) soaking the coaxial fiber resulting from step (a) in a water bath for about 15 hours.
18 . The method of claim 12 , wherein removing the water in step (b) comprises freeze-drying the coaxial fiber, thereby forming the hollow core.
19 . The method of claim 12 , wherein the aqueous cellulose nanofibril suspension comprises about 0.7% by weight of cellulose.
20 . The method of claim 12 , wherein the method comprises:
(a) wet-spinning an organic solution comprising dimethylacetamide, cellulose acetate, and polyacrylic acid, on the exterior of a water core to form a coaxial fiber comprising an exterior and an interior, wherein the coaxial fiber exterior is a cellulose fiber sheath and the coaxial fiber interior is a core filled with water, and wherein the organic solution comprises about 16% by weight of 23:2 w/w of cellulose acetate to polyacrylic acid;
(a1) soaking the coaxial fiber resulting from step (a) in a water bath for about 15 hours;
(b) removing the water from the core, wherein removing the water comprises freeze-drying the coaxial fiber resulting from step (a1);
(c) injecting an aqueous cellulose nanofibril suspension comprising about 0.7% by weight of cellulose into the hollow core of the coaxial fiber resulting from step (b); and
(d) freeze-drying the coaxial fiber resulting from step (c) to form a coaxial fiber comprising an exterior and an interior, wherein the coaxial fiber exterior is a cellulose fiber sheath and the interior is a core comprising a nanofibril aerogel, thereby forming the coaxial fiber of claim 1 .
21 . A method of maintaining a temperature differential between a first zone having a first temperature, and a second zone having a second temperature, comprising:
separating the first zone and the second zone using a plurality of coaxial fibers of claim 1 ; and
applying thermal energy to the first zone such that the first temperature increases while the second temperature of the second zone increases by a lesser amount.
22 . The method of claim 21 , wherein the second zone is a container, a wearable object, clothing, gloves, heat-protective gear, house, building, airplane, trailer, or aircraft.
23 . The method of claim 21 , wherein the method can be performed from a temperature range of about −20° C. to 150° C.