Superior Enhancement of the UHMWPE Fiber/Epoxy ...

Furthermore, by comparing the interfacial shear strength of the fiber before and after the PPy grafting under the same plasma treatment atmosphere, the interfacial shear strength of the fiber was significantly increased by between 109&#;353%. Among them, the PF(N5O5)-PPy had the most significant increase, reaching 353%. In general, both the single experimental method and the method of synergistic treatment can improve the interfacial adhesion performance. It should be noted that the synergistic approach resulted in a noteworthy improvement in the IFSS. The process of the surface treatment using PPy grafting and plasma treatment with the mixture of oxygen and nitrogen achieved the highest increase in the IFSS, which showed a 357% higher enhancement than that of the pristine fibers.

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The debonding test results of the microspheres under the different treatment processes are shown in Figure 4 . It can be seen that the interface shear strength of all the UHMWPE fiber samples subjected to the plasma treatment was higher than that of the untreated fibers. Among them, the interfacial shear strength of the sample PF(N5O5) treated using plasma with the mixed gas was 0.89% higher than that of the untreated fiber, and the sample of PF(N8O2) had the most considerable interface shear strength, which was 32% higher than that of the untreated fiber. The sample PF(N10) treated using pure nitrogen plasma was 1.5% higher than the untreated fiber. This illustrates that the mixed gas plasma treatment process can increase the fiber/matrix interfacial adhesion performance with limited improvement. When the plasma-treated UHMWPE fibers were grafted with PPy, the interfacial shear strength was significantly enhanced. It can be found that the interfacial shear strength of the fibers PF(N5O5)-PPy, PF(N8O2)-PPy, PF(N10)-PPy were increased by 357%, 192%, and 134%, respectively, in which the UHMWPE fiber PF(N5O5)-PPy had an excellent interfacial adhesion performance. This indicated that the UHMWPE fibers surface grafted with PPy could effectively improve the interfacial adhesion performance. Nevertheless, the interfacial shear strength of the untreated fiber was lower than the other fibers grafted with PPy.

The changes in the two microspheres before and after the microsphere debonding test are shown in Figure 3 . It was found that the position of the microsphere moved downward after the test, and the morphology of the microsphere was undamaged. This meant that during the pull-out test, only the shear failure mode was found, making it possible to obtain accurate interfacial shear strength data, as listed in Figure 4

3.2. Tensile Properties

Figure 5 shows the variation of the monofilament tensile strength in the different treatment processes. Among them, the single-filament tensile strength of the untreated fiber sample (UF) was the largest. It indicated that any surface pre-treatment process would decrease the tensile strength of the single filament. Compared to the monofilament tensile strength, it decreased significantly after the plasma treatment. The tensile strength of PF(N5O5), PF(N8O2), and PF(N10) decreased from 7.156 GPa to 3.985 GPa, 3.768 GPa, and 3.298 GPa, respectively. After the PPy grafting, the tensile strength of PF(N5O5), PF(N8O2), and PF(N10) was enhanced to 6.633 GPa, 6.071 GPa, and 5.803 GPa, respectively. It can be seen that the collaborative treatment process appropriately compensated for the excessive fiber strength damage caused by a single treatment method.

The PF(N5O5)-PPy only reduced the tensile strength of the original UF monofilament by 7%. After the plasma was treated, cracks, pits, and grooves appeared on the surface of the UHMWPE fibers. Although these defects reduced the tensile strength of the monofilament, they increased the interface performance between the fiber and matrix [ 24 ]. After the PPy grafting process, the microscopic defects on the monofilament surface could be repaired to a certain extent. Using the combination of the two methods, a significant enhancement of the IFSS of the UHMWPE fiber/epoxy could be achieved without dramatically sacrificing the tensile strength of the fiber.

26,

P σ = 1 &#; 1 &#; F σ N

(3)

F σ = 1 &#; exp &#; σ σ 0 m

(4)

P

(

σ

) illustrates the fracture probability of

N

defects under stress

σ

;

F

(

σ

) represents the tensile stress, which is the cumulative probability distribution function corresponding to σ;

m

is the shape parameter of the fiber, also called the Weibull parameter;

σ

0 indicates the scale parameter under the corresponding test span; and

σ

shows the strength test value of the fiber. The failure probability

F

corresponds to a certain stress level and can be expressed using Equation (5).

F = i N + 1

(5)

N

is the number of samples of the tested single fiber and

i

is the serial number of the strength data obtained from the test sorted from small to large.

The interior and surface of the fiber monofilament introduced certain micro-defects during its production and surface treatment. The distribution of these defects affected the microstructure and tensile strength of the fiber monofilament. On the contrary, the fiber statistical law of the monofilament tensile strength also reflected the law of the influence of the different manufacturing and surface treatment processes on its microstructure. Since the UHMWPE fiber is a fragile material and follows the weakest chain theory, its tensile strength conforms to the two-parameter Weibull distribution function [ 25 27 ]. Therefore, the stress σ can be represented as a one-dimensional Weibull distribution function for the fracture probability, as shown in Equations (3) and (4).where) illustrates the fracture probability ofdefects under stress) represents the tensile stress, which is the cumulative probability distribution function corresponding to σ;is the shape parameter of the fiber, also called the Weibull parameter;indicates the scale parameter under the corresponding test span; andshows the strength test value of the fiber. The failure probabilitycorresponds to a certain stress level and can be expressed using Equation (5).whereis the number of samples of the tested single fiber andis the serial number of the strength data obtained from the test sorted from small to large.

m

and scale parameter

σ

0 of the Weibull distribution function, two logarithms were taken on both sides of Equation (3) to obtain Equation (6).

ln ln 1 1 &#; F = m ln σ &#; m ln σ 0

(6)

In order to obtain the shape parameterand scale parameterof the Weibull distribution function, two logarithms were taken on both sides of Equation (3) to obtain Equation (6).

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lnσ

and lnln(1/(1 &#;

F

)) have a linear relationship. Here, a scatter plot of

lnσ

and lnln(1/(1 &#;

F

)), a one-variable linear regression equation and a Weibull distribution double logarithmic graph, were drawn and analyzed. Among them, the shape parameters of the Weibull equation were obtained by calculating the slope of the straight line equation, and the scale parameters of the Weibull equation were obtained using the intercept. The relevant result is shown in

It can be seen from Equation (6) thatand lnln(1/(1 &#;)) have a linear relationship. Here, a scatter plot ofand lnln(1/(1 &#;)), a one-variable linear regression equation and a Weibull distribution double logarithmic graph, were drawn and analyzed. Among them, the shape parameters of the Weibull equation were obtained by calculating the slope of the straight line equation, and the scale parameters of the Weibull equation were obtained using the intercept. The relevant result is shown in Figure 6 and the parameter calculation result is shown in Table 2

0 was the size of the tensile strength. With the larger values of

σ

0, the values of the strength of the fiber increased. A more intuitive view of the data can be obtained from

The shape parameter m is a characterization of the dispersion of the strength of the fiber monofilament. The larger the m value, the smaller the dispersion of the strength. The scale parameter σwas the size of the tensile strength. With the larger values of, the values of the strength of the fiber increased. A more intuitive view of the data can be obtained from Figure 7 , which shows that the scale parameters of PF(N5O5) and PF(N5O5)-PPy samples were significantly larger. This indicates that the tensile strength of the fiber monofilaments was higher, which was consistent with the findings presented in Figure 5 from a previous study. After the plasma&#;PPy synergistic treatment of the fiber monofilament, the fiber defects were repaired, improving the tensile strength of the monofilament.

In the traditional sense, the strength distribution of the UHMWPE fibers can be described by the standard Weibull distribution function and as a normal Gaussian distribution as well [ 28 ]. The Gaussian distribution probability of the fiber strength density is shown in Figure 6 . Overall, the distribution probability density function image curve peaks of the PF(N10), PF(N10)-PPy, and PF(N8O2)-PPy samples were lower, and the curve width was relatively wide, while the curve peaks in the images of the other three fiber samples were higher and the curve width was narrower. This shows that the dispersion of the former three samples was relatively large, while the dispersion of the latter three samples was relatively small. Moreover, the PF(N505)-PPy, PF(N8O2)-PPy, and PF(N10)-PPy images were shifted to the right compared to the other three fiber strength density distributions that only underwent the plasma treatment, indicating that the fiber strength after the PPy grafting was increased. Compared to Figure 8 , the results were consistent. The image of the PF(N10) fiber sample was to the right of the PF(N5O5) and PF(N8O2) images, which also showed that the tensile strength was higher than the other two fiber samples.

UHMWPE fiber has many features:
l. High specific strength and high specific modulus. The specific strength of the UHMWPE fiber is 1.5 times of the good quality steel wire&#;s and nearly 10 times of the ordinary chemical fiber&#;s.
2. The density of the UHMWPE fiber which is 0.97g/cm3 is less. The fiber can float on the surface of the water.
3. Less breaking elongation but bigger rupture work. The UHMWPE fiber has strong ability to absorb energy so it has excellent impact resistance and cut resistance.
4. Ultraviolet radiation resistance, high specific energy absorption, low dielectric constant and high electromagnetic wave transmission rate.
5. Wear resistance, chemical erosion resistance, longer flex life.

Fishing line

Features of the UHMWPE fiber fishing lines:
Low elongation -- more quick and more accurate casting
Low elongation can offer very tiny and right sense to the fishermen and at the same time fishermen can make the accurate and timely reaction to the moving of the fishing lines.

More secretive in the water:
UHMWPE fiber fishing lines can easily slip all kinds of obstacles to avoid being stuck. The resistance of moving in the water can be less for the less diameter of the fishing lines. The fishing lines can be more secretive and hardly to be found.

Good strength and good sensitivity

Wear resistance and ultraviolet radiation resistance -- more durable
UHMWPE fiber fishing lines have good wear resistance and high durability such as the sunshine and salty water.

Fishing net

UHMWPE fiber fishing nets have lighter and thinner net lines and ropes than nylon and polyester fiber fishing nets, but the UHMWPE fiber lines promise the stability of their properties.

&#; Lighter: The lighter weight can reduce the tension of the system and improve the stability of the net structure and increase the flow.

&#; Stronger: the UHMWPE fiber fishing net can resistant the bites and destructions of the seals and sea wolves effectively.

&#; Little diameter: The UHMWPE fiber fishing net can reduce the drag resistance during in the water which can effectively save the fuel.

&#; Super low weight-strength ratio: It can reduce the tension of the mooring ropes can make it easily to operate the fishing net.

&#; Wear resistance and ultraviolet radiation resistance: longer working life.

&#; Lower water absorption: The UHMWPE fiber fishing nets are easily to be cleaned up and maintained.

Feeding nets

&#; Lighter: The UHMWPE fiber feeding nets need antifouling composition 40% less than the nylon feeding nets. However, the weight of the UHMWPE fiber feeding net is only half of the nylon feeding net which has the same breaking strength. The UHMWPE fiber feeding nets are more easily to be installed and more safely to be operated.

&#; Stronger: The UHMWPE fiber feeding nets can effectively resistant the external attacks and the bites of the feeding fishes so that they can prevent the escape of fishes.

&#; Smaller diameter: there will be less surface pollution and the UHMWPE fiber feeding nets only need to be cleaned up once per 12 months but the nylon nets need to be cleaned up per 7 months. The bigger net mashes make it easier for more water flow through meshes which can make the water cleaner and full of oxygen which means more health to the feeding fishes.

&#; Low Elongation: The low Elongation can help to keep the shape of the net.

&#; More wear resistant: The wear resistance can help to reduce the frequency of the repairmen and prolong the working life of the net. The working life of the UHMWPE fiber feeding nets can be 10years which is 2 times of the traditional nylon net.