KR20180029013A - Measuring method for contact angle of fiber - Google Patents

Abstract

The present invention relates to a method for measuring a contact angle of a fiber. The method for measuring the contact angle of a fiber comprises the following steps: packing the plurality of fibers to maintain a predetermined rate of porosity of the contact angle of a measurement cell; installing the packed fibers vertically in a surface tensiometer; and calculating the contact angle using the density, viscosity, surface tension, a change in mass of wetting liquid over time, and a capillary constant value used in the surface tensiometer.

Description

TECHNICAL FIELD [0001] The present invention relates to a method of measuring a contact angle of a fiber,

The present invention relates to a method of measuring the contact angle of a fiber, which measures the contact angle of the fiber by aligning and packing the fiber bundle in one direction during the measurement of the contact angle of the fiber.

Carbon fiber is a high-strength, high-elastic material that is a new material that can replace materials in the existing steel industry, electric / electronics and various fields. These carbon fibers are difficult to use independently of fibers, and they are mainly used in the form of composite materials and matrix materials such as polymers and metals. When used in the form of composites, the greatest factor in determining properties is the interfacial bonding properties of carbon fibers and matrix materials. Interfacial analysis of carbon fiber is an important factor. Among the various methods for analyzing the interface of carbon fiber, surface free energy analysis through contact angle measurement is largely a method of measuring short fiber contact angle and a method of measuring wetness. Among them, the wet measurement method has been measured at a rate of wetting the contact angle measurement liquid after packing the carbon fibers cut into a certain length into the sample measurement cell using the powder contact angle measurement method. However, there is a problem that the measurement error of the contact angle is large because a certain porosity is not obtained in the form of the fiber other than the powder.

In addition, the method of measuring the short fiber contact angle has a problem that the measurement error of the contact angle is large when the contact angle of the carbon fiber having a diameter of less than 10 μm is too small.

The present invention provides a method of measuring a contact angle of a fiber, which can ensure high accuracy compared to a conventional contact angle measurement method by measuring a contact angle of a fiber by a one-way packing method.

According to an aspect of the present invention, there is provided a method of manufacturing a contact angle measuring cell, comprising the steps of: (a) packing a plurality of fibers to maintain a predetermined porosity in a contact angle measuring cell; (b) installing a plurality of packed fibers vertically in the surface tension meter; And (c) calculating the contact angle using the density, viscosity, surface tension, change in mass of the wetting liquid and capillary constant value of the wetting liquid used in the surface tension meter A method of measuring a contact angle of a fiber can be provided.

After the step (a), the method may further include the step of flatly cutting one end of the packed fiber.

The step (c) may include calculating the capillary constant in a state where the contact angle is 0 using normal hexane in the test liquid, and then calculating the capillary constant using the polarity of the distilled water or the non-polar wetting liquid of diiodonethane The contact angle can be calculated.

으로 계산될 수 있다. (여기서, m은 상기 섬유를 적시는 젖음액의 질량, t는 접촉각 측정시간(초), c는 상기 모세관 상수, η는 젖음액의 점도,

은 상기 젖음액의 표면장력, ρ는 상기 젖음액의 밀도, θ는 상기 섬유와 젖음액의 접촉각 임)The contact angle

. ≪ / RTI > T is the contact angle measurement time in seconds, c is the capillary constant,? Is the viscosity of the wetting liquid,? Is the viscosity of the wetting liquid,

Is the surface tension of the wetting liquid, p is the density of the wetting liquid, and? Is the contact angle of the fiber and the wetting liquid)

And calculating the surface free energy (Γ _S ) of the fiber through the contact angle calculation result after the step (c).

)는

으로 계산될 수 있다. (여기서,

는 상기 섬유의 표면자유에너지 중 극성에너지이며,

는 상기 탄소섬유의 표면자유에너지 중 비극성에너지임)The surface free energy of the fiber

)

. ≪ / RTI > (here,

Is the polar energy of the surface free energy of the fiber,

Is the non-polar energy of the surface free energy of the carbon fiber)

The present invention greatly improves the accuracy compared with the conventional method of measuring the contact angle of carbon fiber, and enables reliable contact angle and surface free energy analysis of the fiber.

Also, based on high precision, it is expected that mechanical interface properties can be predicted according to the change of contact angle and surface free energy depending on the surface treatment of carbon fiber or sizing.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a flow chart sequentially illustrating a method of measuring the contact angle of a fiber according to an embodiment of the present invention.
2 is a view schematically showing a surface tension meter for measuring the contact angle of the carbon fiber shown in Fig. 1; Fig.
3 is a cross-sectional view showing a cross-section of a carbon fiber packed in the contact angle measurement cell shown in FIG. 2;
Fig. 4 is a photograph of the diameter of the carbon fiber shown in Fig. 3; Fig.
FIGS. 5 to 7 are graphs for squares of respective wetting liquid weights according to the time measured in the present invention. FIG.
FIGS. 8 and 9 are graphs showing the results of measuring the contact angle of a single carbon fiber and the results measured by the contact angle measuring method according to an embodiment of the present invention, respectively.

Hereinafter, the description of the present invention with reference to the drawings is not limited to a specific embodiment, and various transformations can be applied and various embodiments can be made. It is to be understood that the following description covers all changes, equivalents, and alternatives falling within the spirit and scope of the present invention.

In the following description, the terms first, second, and the like are used to describe various components and are not limited to their own meaning, and are used only for the purpose of distinguishing one component from another component.

Like reference numerals used throughout the specification denote like elements.

As used herein, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. It is also to be understood that the terms " comprising, "" comprising, "or" having ", and the like are intended to designate the presence of stated features, integers, And should not be construed to preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 1 to 9 attached herewith.

FIG. 1 illustrates a method of measuring the contact angle of a fiber according to an embodiment of the present invention. Referring to FIG. 1, a method of measuring a contact angle of a fiber according to an embodiment of the present invention includes a carbon fiber packing step S100, a step S200 of mounting a carbon fiber on a surface tension meter, a contact angle calculating step S300, (S400).

Specifically, the carbon fiber packing step S100 packs a plurality of carbon fibers so as to maintain a porosity of about 30% in a cylindrical contact angle measuring cell 20 having a diameter of 1/4 inch. At this time, about 576,000 strands of carbon fiber are packed in one direction in the contact angle measuring cell 20 shown in FIG. As shown in FIG. 3, when the carbon fibers are packed in the contact angle measuring cell 20, voids are formed by three adjacent carbon fibers, and these voids can be varied by the diameter of the carbon fibers.

Here, as the diameter of the carbon fiber, as shown in the photograph taken in Fig. 4, a sample of about 7 mu m is used.

Subsequently, the carbon fibers packed in the measuring cell are packed into the measurement cell, and the carbon fibers are cut so that the cut surfaces are constant, and the sample preparation is finished. In this case, it is important to make the cut surface flat since the uniformity of the cut surface of the carbon fiber affects the contact angle measurement.

Next, in step S200 of installing the carbon fibers on the surface tensiometer, the contact angle measuring cell 20 packed with the plurality of carbon fibers 10 is installed perpendicularly to the load cell 30 as shown in FIG. 2 .

The contact angle calculation step S300 is a step of calculating the contact angle by raising the elevation device 50 of the surface tension meter 100 up to the carbon fiber 10 so that the wetting liquid 40 provided on the elevation device 50 moves upward . Contact time should be 300 seconds. At this time, a surface tensiometer (K-100, Kruss, Germany) is used. The measuring section 60 of the surface tensiometer 100 measures the change of the mass of the wetting liquid with time.

Then, the contact angle is calculated using the density, viscosity, surface tension of the used wetting liquid, changes in the mass of the wetting liquid with time, and the capillary constant.

To calculate the contact angle of carbon fiber, use normal hexane, diiodomethane, distilled water as the wetting solution.

For reference, wet contact angle measurement using a surface tensiometer is basically a method of measuring the contact angle of charged particles and a wetting liquid by determining the wetting speed of the wetting liquid rising through voids (pores) of charged particles. In this case, the equation used is expressed by Equation (1).

은 액체의 표면장력 (mN/m), θ는 고체와 액체의 접촉각, t는 접촉각 측정시간 (sec), η는 액체의 점도 (mPa·sec)이다. 수학식 1로부터 고체와 노말헥산(normal Hexane)과 같은 완전 적심 젖음액의 접촉각이 θ=0인 조건에서 시간에 (t)에 따른 액체의 젖음 높이(h)를 측정하여 충전관 내의 공극의 평균반경 (R)을 계산할 수 있다.Where h is the height (cm) of the liquid rising with time, R is the average pore radius (cm) between charged particles,

(T) is the contact angle measurement time (sec), and η is the viscosity of the liquid (mPa · sec). From equation (1), the wetting height (h) of the liquid according to time (t) is measured under the condition that the contact angle of the completely wetted liquid such as solid and normal hexane is θ = 0, The radius R can be calculated.

From the above equation (1), the following assumptions are made when measuring the contact angle of the carbon fiber and the wetting liquid in the contact angle measurement cell. That is, the particle size and filling degree are constant, and the wetting liquid passing through the gap between the plurality of carbon fibers installed in the contact angle measuring cell is turbulent flow, and gravity is ignored. (2) for measuring the mass (m) of the wetting liquid which wetts the particles of the packed bed with time.

은 젖음액의 표면장력 값, η는 젖음액의 점도, m은 접촉각 측정셀내의 탄소섬유를 적시는 젖음액의 질량, t는 시간이다.Where c is the capillary constant, ρ is the density of the wetting fluid,

Is the surface tension value of the wetting liquid, η is the viscosity of the wetting liquid, m is the mass of the wetting liquid that wetts the carbon fibers in the contact angle measuring cell, and t is time.

First, to determine the c value, the viscosity, the density, the surface tension value using a normal hexane, and the wet mass and the slope are determined according to the time, and the capillary constant value .

The capillary constant calculated in this way and the density, viscosity, and surface tension value of the polar liquid or diiodonethane non-polar liquid, distilled water used for the contact angle measurement, The contact angle of the non-polar liquid, which is distilled water, polar liquid or diiodonethane, and the carbon fiber can be determined by measuring the change.

Next, the surface free energy calculation step (S400) calculates the surface free energy using the equations (3) to (5) when the contact angle of the carbon fiber is calculated.

Equations (3) and (4) can be expressed as Equation (5) in order to calculate the surface free energy by the Owens Wendt Rabel and Kaelble (OWRK)

은 고체와 액체사이의 표면자유에너지,

는 고체의 표면자유에너지,

는 액체의 표면자유에너지이다.here,

Is the surface free energy between solid and liquid,

Is the surface free energy of the solid,

Is the surface free energy of the liquid.

)는 극성표면에너지(

)와 비극성 표면에너지(

)의 합으로 계산될 수 있다.In Equation 5, the surface free energy (

) Is the polar surface energy (

) And nonpolar surface energy (

). ≪ / RTI >

For the method of measuring the contact angle of the carbon fiber according to the embodiment of the present invention, the wetting graphs of the respective carbon fibers are shown as a graph relating to the squared weight of the wetting liquid over time as shown in FIGS. 5 to 7.

As shown in FIG. 5, a measurement graph of a normal hexane for obtaining a capillary constant uses a liner fit in a range of 0 to 0.35 seconds.

Also, a graph of a diiodomethane measurement, which is a nonpolar wetting liquid, was analyzed for 0 to 0.35 seconds as shown in FIG. However, the data measured with distilled water is unstable due to the characteristics of non-polar carbon fiber and polar distilled water, and therefore, as shown in FIG. 6, the stable range of 1 second to 2 seconds Respectively.

FIGS. 8 and 9 are graphs showing the results of measuring the contact angle of a single carbon fiber and the results of measuring the contact angle according to the embodiment of the present invention, respectively.

FIG. 8 is a graph showing a contact angle of a single carbon fiber, and the measurement error is about 16%.

On the contrary, the measurement error of the contact angle of the carbon fiber measured by the contact angle measuring method of the carbon fiber according to the embodiment of the present invention is about 2% as shown in the graph of FIG. 9, Can be greatly reduced.

Although carbon fibers have been described in the above, it is easily replaceable by a person skilled in the art to measure the contact angle of thin fibers instead of carbon fibers.

Having described specific portions of the present invention in detail, those skilled in the art will appreciate that these specific descriptions are only for the preferred embodiment and that the scope of the present invention is not limited thereby. It will be obvious. It is therefore intended that the scope of the invention be defined by the claims appended hereto and their equivalents.

10: carbon fiber
20: contact angle measuring cell
30: Load cell
40:
50: lifting device
60:

Claims (1)

(a) 576000 fibers having a diameter of 7 占 퐉 were packed in one direction so as to maintain a porosity of 30% in a cylindrical contact angle measuring cell having a diameter of 1/4 inch, and the fiber top was fixed to the contact angle measuring cell step;
(b) installing a plurality of packed fibers vertically in the surface tension meter; And
(c) calculating a contact angle using the density, viscosity, surface tension, change in mass of the wetting liquid and capillary constant value of the wetting liquid used in the surface tension meter; and ,
The step (c)
The lifting device of the surface tension meter is raised to the fiber so that the wetting liquid provided on the lifting device contacts the fiber for 300 seconds,
The measuring unit of the surface tensiometer measures a change in mass of the wetting liquid with time,
After step (a)
Further comprising the step of flatly cutting one end of the packed fiber,
The step (c)
After calculating the capillary constant in a state where the contact angle is 0 using normal hexane in the wetting liquid,
The contact angles of the polar wetting liquid, which is distilled water, or the nonpolar wetting liquid, which is diiodonethane,
The contact angle

Lt; / RTI >
T is the contact angle measurement time in seconds, c is the capillary constant,? Is the viscosity of the wetting liquid,? Is the viscosity of the wetting liquid,

Is the surface tension of the wetting liquid, p is the density of the wetting liquid, and? Is the contact angle of the fiber and the wetting liquid)
After step (c)
The contact angle calculation results indicate that the surface free energy of the fiber

), ≪ / RTI >
The surface free energy of the fiber

)

Lt; / RTI >
remind

Quot;

And

Of the fibers are obtained by simultaneous measurement of the contact angle of the fibers.
(here,

Is the polar energy of the surface free energy of the fiber,

Is the non-polar energy of the surface free energy of the fiber)

Images