US20140212598A1

US20140212598A1 - Protection and performance improvements of fabrics through nanotechnology

Info

Publication number: US20140212598A1
Application number: US14/161,316
Authority: US
Inventors: Reed F. Curry
Original assignee: Uvr Defense Tech Ltd
Current assignee: UVR DEFENSE Technology Ltd; Uvr Defense Tech Ltd
Priority date: 2013-01-26
Filing date: 2014-01-22
Publication date: 2014-07-31

Abstract

A system and method for treating fabrics to increase tear strength and to decrease UV exposure of the fabrics to help mitigate degradation in strength, color, or other significant attributes of the fabric. Nanoparticles are embedded within thin films and applied to the fabrics to increase the tear strength of such fabrics and minimize UV exposure.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 61/757,123, filed Jan. 26, 2013, the contents of which are incorporated by reference herein in their entirety.

FIELD OF THE INVENTION

The invention relates to fabrics, and more particularly to fabrics that degrade in strength, color, or other significant attributes, due to exposure to ultra-violet wavelengths of light, wherein the use of nanoparticles embedded within thin films mitigates degradation of the fabrics and increases the tear strength of such fabrics.

BACKGROUND OF THE INVENTION

Various fabrics are significantly adversely affected by exposure to ultraviolet light (“UV”). UV, as used herein, refers to wavelengths of light between about 280 nm and about 400 nm. Fabrics, which are woven of yarns known as aramids, or “aromatic” “polyamides,” are especially susceptible to UV exposure. Some exemplary product names for these fabrics are KEVLAR, PBI, and NOMEX. Aramid fabrics include, but are not limited to, meta-aramids and para-aramids. Aramid fabrics are typically used as “ballistic fabric” due to great tensile and great tear strength. Ballistic fabrics are used in the textile industry for making cables, ropes, pre-forms for composites, bulletproof vests, cut-resistant articles, firefighters' turnout gear, airbags for passenger cars, tendons for giant scientific balloons, and the like. However, exposure to solar UV light can greatly reduce the tear strength of these fabrics quite rapidly.
It is recognized that there is a need for a solution to this degradation of ballistic fabrics caused by UV light. Such a solution could extend the life of the fabric significantly. Currently, due to the deleterious effects of UV exposure, firefighters' turnout gear—jackets, pants, etc.—are often replaced every five years at a cost in excess of five thousand dollars per suit. The military, as well, spends large sums of money on premature replacement of body armor and many other items made in whole or in part of ballistic fabric. It is considered prudent to proactively scrap some gear prior to signs of failure rather than expose a soldier to the dangers resulting from gear failure.
Currently, one solution to shield fabric from UV wavelengths is to coat the fabric in a solid, highly-reflective film, such as thin aluminum. This is a flawed solution because it is necessary for many applications of aramid fabric that the fabrics pass vapor from the user to the external air, otherwise the wearer would suffer hyperthermic stress from excessive heat buildup. Thus, solid films are unsuitable for such applications. Similarly, covering the ballistic fabric with a lightweight, porous, UV-reflective fabric is insufficient, because it is the ballistic fabric that provides great strength and flame-resistance to the object and covering that fabric with another layer of fabric would defeat these benefits.

SUMMARY OF THE INVENTION

One aspect of the present invention is a method for treating fabrics to increase tear strength, comprising, forming an aqueous solution, comprising, nanoparticles that prevent more than 50% of UV light in the range of 280 nm to 400 nm from reaching the fabric; applying the aqueous solution to the fabric; and drying the fabric with heat at less than 110° C., thereby forming a coated fabric, wherein the appearance of the coated fabric will not be significantly altered in visible light.
One embodiment of the present invention is wherein the aqueous solution comprises ceramic nanoparticles. One embodiment of the present invention is wherein the aqueous solution comprises cerium oxide nanoparticles. One embodiment of the present invention is wherein the aqueous solution comprises zinc oxide nanoparticles.
One embodiment of the present invention is wherein the aqueous solution comprises cerium oxide and zinc oxide nanoparticles.
One embodiment of the present invention is wherein the nanoparticles have low thermal conductivity.
One embodiment of the present invention is wherein the nanoparticles prevent about 50% of UV light in the range of 320 nm to 400 nm. from reaching the fabric.
One embodiment of the present invention is wherein the tear strength of the coated fabric is increased by more than 10 percent. One embodiment of the present invention is wherein the tear strength of the coated fabric is increased by more than 40 percent.
One embodiment of the present invention is wherein the aqueous solution comprises nanoparticles with hydrophobic properties.
One embodiment of the present invention is wherein the aqueous solution further comprises an additive. One embodiment of the present invention is wherein the additive is a particle binder, a wax softener, a surfactant, a particle agglomeration preventer, a DWR, or a combination thereof.
One embodiment of the present invention is wherein the fabric is aramid-based.
One embodiment of the present invention is wherein the aqueous solution is applied by pad and mangle, knife over roller, or spraying. One embodiment of the present invention is wherein the aqueous solution is applied in solid form, a film, or a powder by transferring the solution to the fabric through the application of heat, pressure, or a combination thereof.
One embodiment f the present invention is further comprising sonicating the aqueous solution.
One embodiment of the present invention is wherein the coated fabric is non-flammable.
One embodiment of the present invention is wherein the nanoparticles absorb UV light in the range of 280 nm to 400 nm. One embodiment of the present invention is wherein the nanoparticles reflect UV light in the range of 280 nm to 400 nm.
One embodiment of the present invention is wherein the fabric comprises a plurality of individual yarns, and the coated fabric comprises a surface coating on the individual yarns, but does not bind the individual yarns to each other.
These aspects of the invention are not meant to be exclusive and other features, aspects, and advantages of the present invention will be readily apparent to those of ordinary skill in the art when read in conjunction with the following description, appended claims, and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features, and advantages of the invention will be apparent from the following description of particular embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention.

FIG. 1 shows a UV-visible diffuse reflectance spectrum of CeO₂particles.

FIG. 2 shows a UV-visible diffuse reflectance spectrum of ZnO particles.

FIG. 3 shows a model of “bridging” between fibers of the warp and the weft yarns of woven fabric.

DETAILED DESCRIPTION OF THE INVENTION

Aramid fibers, or aromatic polyamides, are a class of heat-resistant, flame-resistant, and inherently strong, synthetic fibers. Aramid fibers have many applications including, but not limited to, aerospace and military applications, as firefighter turn-out gear, as ballistic rated body armor fabric, as ballistic composites, and as an element of FRP (fiber-reinforced plastic) in small-boat construction.
The chain molecules in aramid fibers are highly oriented along the fiber axis, so the strength of the chemical bond can be exploited. Some of the more common trade names of aramid fibers, as well as meta-aramids, are readily recognized, KEVLAR, TWARON, NOMEX, PBI/KEVLAR.
When aramids, para-aramids, meta-aramids, and the like are woven into fabric, the strength-to-weight ratios become very high. However, these fabrics readily degrade upon exposure to ultraviolet light, losing seventeen percent or more of their tear strength in a few hours. These fabrics are known to lose more than fifty percent of their tear strength after one hundred and twenty hours. The industry has made many attempts to provide a coating for these fabrics that would act as a shield against ultraviolet-induced degradation. Generally, this has taken the form of sol-gels of Zinc oxide or Titanium dioxide. However, the manner of application of the protective coating has caused a serious degradation in the tear strength of the fabric.
Previous attempts have been made to decrease the photo-degradation of aramids through the application of sol-gels of Titanium Dioxide (TiO₂) to the fabric. In contrast to conventional coating processes such as evaporation and sputtering, sol-gel coating can be done at room temperature and normal atmospheric pressure environment. Sol-gel coating has been used to create a transparent metal oxide film that adheres well to the fiber surface to improve textile properties such as abrasion resistance, electrical conductivity. UV protection, biocompatible properties and the like. However, sol-gel coating has not been successful in preserving the tear strength of aramid fabrics. In the thesis work of Dr. Lidan Song, a sol-gel, which deposited TiO₂on aramid fabrics was studied. The sol-gel added significantly to the weight of the fabric as seen in Table 1 from Song's work:

TABLE 1

Add-on weight of TiO₂on coted NOMEX fabric

Original

Low concentration coating

High concentration coating

mass^a	Masss^a	Increase	Mass^a	Increase
(g/m²)	(g/m²)	(%)	(g/m²)	(%)

A	183.9	196.2	6.7	200.8	9.2
B	196.5	207.9	5.8	212.2	8.0
C	254.8	264.0	3.6	272.4	6.9

As can be seen in Table 1, an 8-9% increase in weight of the fabric occurs with the application of the sol-gel. This is unacceptable, because the users of aramids firefighting, etc.—are looking for ways to save weight, not increase it.
In one embodiment of the present invention, the weight of a typical PBI/KEVLAR fabric was increased by 3.46 g per square meter. This is an increase of only 1.4%. See, Table 2, below.

TABLE 2

Add-on weight of an solution of die
present invention on PBI/KEVLAR

Original Mass	After coating
(g/m²)	Mass(g/m²)	Increase (%)

242.79	246.25	1.4

The slight increase in weight by application of an embodiment of the present invention is more than compensated by the increase in tear strength. In independent tests, one embodiment of the present invention produced an increase in the tear strength of a PBI/KEVLAR fabric from 115 N to 223 N. In contrast, the use of sol-gel decreases the tear strength as seen in Table 3, below (from Dr. Song's work):

TABLE 3

Breaking strength (n = 5) of original uncoated, low concentration
and high concentration sol-gel coated fabric C vs. light exposure.

	Original	Low concen-	High concen-
Light	uncoated	tration	tration
exposure	Maximum	Maximum	Maximum
(AFU)	Load (N)	Load (N)	Load (N)

	0	565.7	315.5	337.3
	20	480.1	267.3	308.7
	40	390.0	241.3	274.9
	60	340.1	229.0	259.1
	80	297.8	202.1	234.3
	120	240.8	176.9	205.3

Original uncoated fabric C mass = 255 g/m²

Note that the breaking strength drops from 565.7 N to 337.3 N (N=Newtons, a measure of force) just by applying the sol-gel. The fabrics' breaking strengths drop to about half of the original breaking strength after sol-gel coating both in high and low concentration sol solutions. In one example, the fabric had an initial breaking strength of 438.3 N and the breaking strength decreased to 262.2 N when coated with the low concentration sol-gel and 276.8 N after coating with the high concentration sol-gel.
According to Dr. Song, this loss of breaking strength may be explained in a couple of ways. First, the loss of breaking strength may be caused by the structural change of the fabric, because the film not only covers the fiber surface but also bridges the gaps between the individual, fibers. The fibers become stuck together by the inorganic TiO₂thin film after sol-gel coating. The TiO₂thin film decreases the flexibility of individual fibers. At the same time, the TiO₂films increase the friction between single fibers. The inflexibility and the change in the fiber friction restrict the movement of the individual fibers. This reduction of the free movement prevents the readjustment of fibers when stressed, and therefore decreases the chance for fibers to join together to share the load when a load is applied. As a result, fibers of the sol-gel coated fabric tend to break at a lower load in comparison to original uncoated fabric while a load is applied. A second possible contributing factor to the loss of initial breaking strength is the combined effect of the presence of nitric acid HNO₃in the TiO₂sol solution and the heat treatment afterwards.
In one embodiment of the present invention, the coating on the individual fibers does not cover the gaps between individual fibers. In certain embodiments, added friction from the use of Cerium oxide (CeO₂) nanoparticles causes the fibers to work together without causing yarn bundles to bind. In certain embodiments of the present invention, strong acids and/or high heat are not used to bond the nanoparticles to the fabric.
Another aspect of the present invention uses CeO₂, which has better absorbance in the UVA. In certain embodiments, ZnO is also used. In contrast, the sol-gel method applies TiO₂, which has some gap in absorbance in the 380 nm to 400 nm range. Additionally, TiO₂generates free radicals, which in turn increase the speed of photodegradation of the surface. CeO₂, on the other hand, scavenges free radicals, even through the polymer coating, thus interrupting the degradation process. Another benefit of free-radical scavenging, is the inhibition of bacterial growth. In a recent study, coated CeO2 particles were tested against Pseudomonas aeruginosa, a common bacteria seen on infected medical devices. After 24 hours the growth of Pseudomonas aeruginosa was inhibited by over 50% in the presence of the polymer coated CeO₂.
In one embodiment of the present invention a tough, micro-thin coating of nanoparticles is applied to Kevlar®, PBI/Kevlar, or other aramid, meta-aramid, or para-aramid ballistic fabrics to absorb, and/or reflect, greater than about 90% of the incident ultraviolet light in the 280 nm to 400 nm range. By absorbing or reflecting the UV light before it can strike the fabric, the useful life of ballistic fabric is greatly extended.
In one embodiment of the present invention, a highly UV-absorbent suspension of nanoparticles is applied to Kevlar®, PBI/Kevlar, or other aramid, meta-aramid, or para-aramid ballistic fabrics, and confers long-term protection against the degradation caused by ultraviolet light while also increasing the tear strength of the fabric.
Both Kevlar® and PBI/Kevlar® fabrics absorb most of the ultraviolet light (UV) striking them. Energy in UV wavelengths causes a rapid decline in fabric tear strength and ballistic resistance. As much as a seventeen percent loss in tear strength has been seen in only three hours of exposure to normal sunlight. An application of one embodiment of the present invention provides a tough, micro-thin coating of nanoparticles to the fibers of the ballistic fabric.
In certain embodiments, the nanoparticles absorb greater than about 90% of incident ultraviolet light in the 280 nm to 400 nm range. In certain embodiments, the nanoparticles absorb greater than about 10% of incident ultraviolet light in the 280 nm to 400 nm range. In certain embodiments, the nanoparticles absorb greater than about 20% of incident ultraviolet light in the 280 nm to 400 nm range. In certain embodiments, the nanoparticles absorb greater than about 30% of incident ultraviolet light in the 280 nm to 400 nm range. In certain embodiments, the nanoparticles absorb greater than about 40% of incident ultraviolet light in the 280 nm to 400 nm range. In certain embodiments, the nanoparticles absorb greater than about 50% of incident ultraviolet light in the 280 nm to 400 nm range. In certain embodiments, the nanoparticles absorb greater than about 60% of incident ultraviolet light in the 280 nm to 400 nm range. In certain embodiments, the nanoparticles absorb greater than about 70% of incident ultraviolet light in the 280 nm to 400 nm range. In certain embodiments, the nanoparticles absorb greater than about 80% of incident ultraviolet light in the 280 nm to 400 nm range.
In certain embodiments, the nanoparticles reflect greater than about 90% of incident ultraviolet light in the 250 nm to 400 nm range. In certain embodiments, the nanoparticles reflect greater than about 10% of incident ultraviolet light in the 250 nm to 400 nm range. In certain embodiments, the nanoparticles reflect greater than about 20% of incident ultraviolet light in the 250 nm to 400 nm range. In certain embodiments, the nanoparticles reflect greater than about 30% of incident ultraviolet light in the 250 nm to 400 nm range. In certain embodiments, the nanoparticles reflect greater than about 40% of incident ultraviolet light in the 250 nm to 400 nm range. In certain embodiments, the nanoparticles reflect greater than about 50% of incident ultraviolet light in the 250 nm to 400 nm range. In certain embodiments, the nanoparticles reflect greater than about 60% of incident ultraviolet light in the 250 nm to 400 nm range. In certain embodiments, the nanoparticles reflect greater than about 70% of incident ultraviolet light in the 250 nm to 400 nm range. In certain embodiments, the nanoparticles reflect greater than about 80% of incident ultraviolet light in the 250 nm to 400 nm range.
Data on % reflectance was obtained by photographing the treated fabric of the present invention in solar wavelengths filtered with an ultraviolet band pass filter (e.g., the PrecisionU made by UVROptics). Reflectance standards that reflect the same percentage of light in all wavelengths from 250 nm to 1150 nm are placed in the photos, as camera sensors typically only get down to about 320 nm. According to the standards, the CeO₂+ZnO embodiment of the present invention reflects 7% of the ambient solar UV (between 320 nm and 400 nm—the camera sensor used did not record below 320 nm).
In one embodiment of the present invention, ZrO₂nanoparticles are used and results in approximately 90% UV reflectance between 320 nm and 400 nm (the camera sensor used did not record below 320 nm).
The UV-visible diffuse reflectance spectrum of CeO₂particles can be seen in FIG. 1. The CeO₂UV-visible diffuse reflectance spectrum when compared to the UV-visible diffuse reflectance spectrum of ZnO in FIG. 2 shows that the ZnO particles increase in percentage absorption of UV faster than the CeO₂particles do; however, the CeO₂particles absorbance begins sooner. Additionally, CeO₂nanoparticles have other desirable properties, e.g., hardness, electrostatic dissipation, etc., which make them a nice choice for certain embodiments of the present invention.
Firefighter turnout gear treated with one embodiment of the present invention also reflects significantly more of the infrared (“IR”) wavelengths (e.g., from Near IR through Thermal IR) than the base fabric alone. This results in less heat penetration and therefore less stress for the wearer. In certain embodiments, the nanoparticles are ceramic and have low thermal conductivity; thus, they do not contribute to the wearer's heat load.
Friction between individual fibers in the ballistic fabric is beneficial, but friction between overlapping yarn strands is not. In FIG. 3, a representation of “bridging” between the warp and the weft yarn in the fabric is shown. This is an explanation as to why the sol-gel approach decreases the tear strength of these fabrics.
In certain embodiments of the present invention, the particles are small (e.g., 10 nm to 50 nm in diameter). This is compared to a human hair, which is about 90,000 nm in diameter. In certain embodiments of the present invention, the binder is diluted; allowing a thin film to cover the individual fibers, but the film is too thin to bind the yarn strands to one another or cover gaps between yarn bundles (“bridge”). The friction between the fibers created by the nanoparticles and binder of the present invention is longitudinal, thus causing the fibers to move and work together rather than slipping over one another. This is, in part, what increases the tear strength of the fabrics treated in certain embodiments of the present invention.
For simplicity, the fabric herein is discussed in reference to aramid-based fabrics, but one of skill in the art would appreciate that the embodiments of this invention would be applicable to other fabrics. In one embodiment of the present invention, the fabric comprises a synthetic fiber. In one embodiment of the present invention, the fabric comprises a natural fiber. In one embodiment of the present invention, the fabric comprises an aramid. In one embodiment of the present invention, the fabric comprises a polyester. In one embodiment of the present invention, the fabric comprises a polyamide. In one embodiment of the present invention, the fabric comprises a polypropylene. In one embodiment of the present invention, the fabric comprises rayon. In one embodiment of the present invention, the fabric comprises a composite fiber.
Friction between a projectile and a ballistic fabric has a positive effect on fabric energy absorption by influencing the number of yarn strands that become involved in dispersing the energy. One embodiment of the present invention increases the friction between the projectile and fabric through the millions of nanoparticles adhering to the yarns; reducing slippage and increasing the likelihood of more yarn involvement in absorbing the projectile strike. Additionally, a 2003 U.S. Army sponsored study, found that the hardness of silica particles entrained in a Kevlar fabric contributed to the puncture and ballistic resistance of the fabric. The nanoparticles of present invention are significantly harder than the silica particles used in the study.
In one embodiment of the present invention, a very thin film is applied to the fabric such that it does not bind the yarns together, thus reducing the chance of yarns being torn during pullout. In certain embodiments, the film is on each fiber of the fabric but does not span the pores of the weave, and as such does not alter the breathability of the garment. In certain embodiments, the nanoparticles are electro-static dissipative, slowly bleeding any acquired static electricity rather than producing a dangerous spark.
It is understood that the embodiments of the present invention may be applied by knife-over-roller, pad and mangle, or other common textile treatment techniques. In certain embodiments of the present invention, the solution may be applied in a solid form including, but not limited to, a film, a solid, a powder and the like, where the solution is transferred to the fabric using heat, pressure, or both. In certain embodiments, the solution is applied with a hot iron. In certain embodiments of the present invention, high heat is not required to bond the nanoparticle film to the fabric as is common with sol-gels. In one embodiment of the present invention, the solution is water-based and non-toxic treatment with no volatile organic compounds (VOCs).
In certain embodiments of the present invention, durable water repellent or durable water resistant (“DWR”) compounds may be integrated with the nanoparticles in order to protect ballistic fabric from water absorption. It is understood that wet ballistic fabric loses much of its stopping power through yarn slippage.
It has been shown that fabric with a higher level of friction absorbs larger amounts of energy. In one study, Bazhenov investigated the effect of water on the ballistic performance of a rectangular laminate comprised of 20 layers of ARMOS fabric. The specimens were attached to a plasticine foundation and struck with projectiles possessing spherical tips. The dry laminate stopped the bullet while the wet laminate was perforated. It was observed that the impacted yarns in the wet laminate were not broken indicating that the yarns moved laterally and allowed the bullet to slide through the fabric. Based on this observation, Bazhenov surmised that the water served as a lubricant that decreased friction between the bullet and the yarns.
Experimental:
One embodiment of the present invention uses UV absorbent nanoparticles. The following mixture is an example of one embodiment of the fabric treatment of the present invention. The treatment was tested on KEVLAR and KEVLAR/PBI. The following table presents the relative weights of each of the ingredients and the relative percent of each component used in the fabric treatment.

TABLE 4

	(g)	%	(g)

Distilled water	90.0	~46.6%		90.0
Acrylic or urethane binder in Aqueous	60.0	~31.1%		60.0
suspension
Zinc Oxide NP in Aqueous Suspension	10.0	~5.2%		10.0
Wax Softener in Aqueous Suspension	3.0	~1.6%		3.0
Cerium Oxide NP in Aqueous Suspension	30.0	~15.5%		30.0
			Total	193

NP = nanoparticles

The components in Table 4 were mixed thoroughly. In certain embodiments, sonication was used to avoid excessive aggregation. Some aggregation will occur, but it should not be visible. No agglomeration or flocculation should be present. The solution was warmed to 100° F before applying to the fabric. The solution was applied to the fabric with padding and mangle. The mangle was heated to 400° F. The ballistic fabric was immersed in warm water, passed through the heated mangle, immersed in the solution, and hung to drip. The coated fabric was then passed through the heated mangle several times. In a production environment, the fabric might be passed through a mangle once and then into a stenter for drying.
One embodiment of the present invention uses UV reflective nanoparticles. The following mixture is an example of one embodiment of the fabric treatment of the present invention. The treatment was tested on KEVLAR and KEVLAR/PBI. The following table presents the relative weights of each of the ingredients and the relative percent of each component used in the fabric treatment.

TABLE 5

	(g)	%	(g)

Distilled water	90.0	~46.6%		90.0
Acrylic or urethane binder in	60.0	~31.1%		60.0
Aqueous suspension (e.g. a DWR
in aqueous suspension, such as
NanoSphere by Schoeller)
Wax Softener in Aqueous Suspension	3.0	~1.6%		3.0
Magnesium Oxide NP in Aqueous	40.0	~20.7%		30.0
Suspension
			Total	193

NP = nanoparticles

The components in Table 5 were mixed thoroughly. In certain embodiments, sonication was used to avoid excessive aggregation. Some aggregation will occur, but it should not be visible. No agglomeration or flocculation should be present. The solution was warmed to 100° F. before applying to the fabric. The solution was applied to the fabric with padding and mangle. The mangle was heated to 400° F. The ballistic fabric was immersed in warm water, passed through the heated mangle, immersed in the solution, and hung to drip. The coated fabric was then passed through the heated mangle several times. In a production environment, the fabric might be passed through a mangle once and then into a sterner for drying.
The nanoparticles of the present invention are from about 10 nm to about 50 nm. In certain embodiments, the nanoparticles are from about 13 nm to about 40 nm. In certain embodiments, the nanoparticles are from about 15 nm to about 30 nm. In certain embodiments, the nanoparticles are about 10 nm, about 12 nm, about 14 nm, about 16 m, about 18 nm, or about 20 nm. In certain embodiments, the nanoparticles are about 22 nm, about 24 nm, about 26 nm, about 28 nm, or about 30 nm. In certain embodiments, the nanoparticles are about 32 nm, about 34 nm, about 36 nm, about 38 m, or about 40 nm. In certain embodiments, the nanoparticles are about 42 nm, about 44 nm, about 46 nm, about 48 m, or about 50 nm.
In certain embodiments of the present invention, aggregates of the nanoparticles are less than about 100 nm.
In certain embodiments of the present invention, the nanoparticles are ceramic. In certain embodiments of the present invention, the nanoparticles are oxides. In certain embodiments of the present invention, the nanoparticles are non-oxides. In certain embodiments of the present invention, the nanoparticles are cerium oxide. In certain embodiments, the nanoparticles are zinc oxide. In certain embodiments of the present invention, the nanoparticles are zirconium oxide. In certain embodiments of the present invention, the nanoparticles are aluminum oxide. In certain embodiments of the present invention, the nanoparticles are magnesium oxide.
In one embodiment of the present invention, the nanoparticles are cerium oxide and are approximately 13 nm in size in an aqueous suspension combined with nanoparticles of zinc oxide that are approximately 20 nm in size in an aqueous suspension.
In certain embodiments, additives can be used with the nanoparticles. Some forms of additives can be an acrylic or urethane used as a particle binder, a stearate such as magnesium stearate to prevent particle agglomeration, a surfactant, a wax for softening, and/or a durable water repellent such as NanoSpheres from Schoeller.
Independent tests of the fabric treatments of the present invention demonstrate improved tear strength, as shown in Table 6, below, where the fabric tested was PBI/Kevlar. The fabrics were tested using the wing-rip method.

TABLE 6

	Treated	Untreated

	Warp: 213 N	Warp: 115 N
	Weft: 149 N	Weft: 100 N

As can be seen in Table 6, the tear strength of the ballistic fabric is improved in both the Warp and Weft directions. The tear strength in the Warp direction is nearly doubled, and the tear strength m the Weft direction is increased by nearly 50%.
As used herein “solution” is used for simplicity, but it is understood that solution represents a mixture and that mixture might be an emulsion, a suspension, a solution, a solid, and the like.
As used herein “fabric” means a product comprising fibers including, but not limited to, cloth that is woven, knitted, felted and the like; rope; cable; netting; webbing; and the like.
As used herein, an “aqueous” solution means a mixture comprising more than 10% water. In certain embodiments, the aqueous solution of the present invention will comprise other solvents or carriers including, but not limited to, alcohols.
While the principles of the invention have been described herein, it is to be understood by those skilled in the art that this description is made only by way of example and not as a limitation as to the scope of the invention. Other embodiments are contemplated within the scope of the present invention in addition to the exemplary embodiments shown and described herein. Modifications and substitutions by one of ordinary skill in the art are considered to be within the scope of the present invention.

Claims

What is claimed:

1. A method for treating fabrics to increase tear strength, comprising,

forming an aqueous solution, comprising,

nanoparticles that prevent more than 50% of UV light in the range of 280 nm to 400 nm from reaching the fabric;

applying the aqueous solution to the fabric; and

drying the fabric with heat at less than 110° C., thereby forming a coated fabric, wherein the appearance of the coated fabric will not be significantly altered in visible light.

2. The method of claim 1, wherein the aqueous solution comprises ceramic nanoparticles.

3. The method of claim 1, wherein the aqueous solution comprises cerium oxide nanoparticles.

4. The method of claim 1, wherein the aqueous solution comprises zinc oxide nanoparticles.

5. The method of claim 4, wherein the aqueous solution comprises cerium oxide nanoparticles.

6. The method of claim 1, wherein the nanoparticles have low thermal conductivity.

7. The method of claim 1, wherein the nanoparticles prevent about 50% of UV light in the range of 320 nm to 400 nm from reaching the fabric.

8. The method of claim 1, wherein the tear strength of the coated fabric is increased by more than 10 percent.

9. The method of claim 1, wherein the tear strength of the coated fabric is increased by more than 40 percent.

10. The method of claim 1, wherein the aqueous solution comprises nanoparticles with hydrophobic properties.

11. The method of claim 1, wherein the aqueous solution further comprises an additive.

12. The method of claim 11, wherein the additive is a particle binder, a wax softener, a surfactant, a particle agglomeration preventer, a DWR, or a combination thereof.

13. The method of claim 1, wherein the fabric is aramid-based.

14. The method of claim 1, wherein the aqueous solution is applied by pad and mangle, knife over roller, or spraying.

15. The method of claim 1, wherein the aqueous solution is applied in solid form, a film, or a powder by transferring the solution to the fabric through the application of heat, pressure, or a combination thereof.

16. The method of claim 1, further comprising sonicating the aqueous solution.

17. The method of claim 1, wherein the coated fabric is non-flammable.

18. The method of claim 1, wherein the nanoparticles absorb UV light in the range of 280 nm to 400 nm.

19. The method of claim 1, wherein the nanoparticles reflect UV light in the range of 280 nm to 400 nm.

20. The method of claim 1, wherein the fabric comprises a plurality of individual yarns, and the coated fabric comprises a surface coating on the individual yarns, but does not bind the individual yarns to each other.