JPH0519785Y2 - - Google Patents

Description

[Detailed explanation of the idea] [Industrial application field] The present invention relates to a load measuring device.

[Prior Art] Polar group portions on the surface of a polymeric material are oriented so as to minimize interfacial free energy with the surrounding environment during molding or film formation. This preferred orientation is not permanent and can only change orientation in response to the external environment if micro-Brownian motion of the surface segments is allowed. In addition, the surface chemical composition of multiphase polymer materials is significantly different from that inside, and if microphase separation is good, hydrophobic groups are quickly oriented on the surface in air and hydrophilic groups in water, and the chemical composition is highly resistant to the environment. is known to respond in an extremely short time.

Therefore, when looking at the evaluation of surface properties depending on the intended use of the material, for example segmented polyurethane (SPUU) used in artificial hearts, it is difficult to evaluate the surface properties of the parts that come into contact with water, which is the main component of living organisms. is important.

Therefore, one method to evaluate the surface properties of materials is to measure the surface tension when moving a sample, such as a solid polymer, from air to water or from water to air. One possible method is to evaluate the reorganization behavior of the aggregated state of the chains. In addition, in such cases, a load cell that suspends and supports the sample and a container holder that supports the liquid container are provided, and by moving the load cell and the container holder relative to each other, the sample can be immersed or pulled up into the liquid. It is conceivable to use a load measuring device that measures changes in the load acting on the sample.

[Problems to be solved by the invention] By the way, when using a load measuring device such as the one described above to evaluate the surface characteristics of a material, the load cell stably measures only changes in the load caused by the surface characteristics of the material. It is desirable to be able to measure the surface properties of a material with high precision.

This invention enables stable measurement of only changes in load due to the surface characteristics of the sample when immersing or pulling up a sample suspended from a load cell into a liquid and measuring the load acting on the sample. The purpose is to

[Means for solving the problems] The present invention includes a load cell that suspends and supports a sample, a container pedestal that supports a liquid storage container,
This is a load measuring device that measures changes in the load acting on a sample immersed or pulled up in a liquid by relatively moving a load cell and a container holder.The load cell is fixedly disposed on the mount, and the container holder is The pedestal is arranged to be movable up and down on the pedestal, and is provided with an up/down drive section for raising and lowering the container holder.

[Function] When a sample suspended and supported by a load cell is immersed or pulled up into a liquid and the load acting on the sample is measured, two methods are considered: moving the load cell and moving the liquid container.

In the method, when the load cell is accelerated or decelerated, for example while the lifting platform supporting the load cell reaches a constant speed from a stopped state (see Fig. 6A), the sample (mass: m) has an acceleration α (See Figure 6B). The load T1 acting on the load cell when stopped is T1=mg, and the load T2 acting on the load cell during acceleration is T2=mg+mα. That is,
The load T2 acting on the load cell during acceleration increases (or decreases) by mα under the influence of acceleration α,
The load cell will detect this. Also,
When the above acceleration α is suddenly applied (or removed) using the method described above, the spring system (spring constant: k) consisting of the load cell and the sample vibrates according to the equation of motion mα = -kx (6th (See Figure C).

On the other hand, in the method of (2), it is possible to eliminate the influence of the acceleration α and sample vibration on the load detected by the load cell, and the load cell can stably detect only changes in the load caused by the surface characteristics of the sample. can be measured.

[Example] Fig. 1 is a schematic diagram showing an example of a dynamic contact angle measuring device, Fig. 2 is a block diagram showing a control system of the dynamic contact angle measuring device, and Fig. 3 is a piping diagram showing a temperature control device. , Figure 4 is a schematic diagram showing the load acting on the sample,
FIG. 5 is a diagram showing the dynamic contact angle hysteresis loop, FIG. 6 is a schematic diagram showing the influence of acceleration acting on the sample, and FIG. 7 is a schematic diagram showing the displacement of the load cell.

The dynamic contact angle measuring device 10 is configured as shown in FIGS. 1 and 2, and a sample 11 is placed in a liquid container 12.
The contact angle θ between the liquid surface and the sample surface can be measured at the position where the liquid surface touches the sample wall when the sample is immersed in or pulled up from the liquid inside the sample. The dynamic contact angle measurement device 10 includes a pedestal 13, a load cell 14, a container pedestal 15, a lifting drive section 16, a temperature control device 17, and a control device 18.

That is, the frame 13 of the dynamic contact angle measuring device 10
A fixed crosshead 19 is fixed to the upper part of the guide rod 13A, and the fixed crosshead 19 is equipped with a load cell 14. The load cell 14 is
A chuck 22 is suspended from a hook 20 connected to the sensing portion via a flexible connector 21 made of thread, thin metal wire, chain, etc., and the sample 11 is held in the chuck 22. The load cell 14 measures load using a highly sensitive strain gauge. The sample 11 is made of, for example, a polymer material and is thinly coated on a flat cover glass.

The dynamic contact angle measuring device 10 also includes a container holder (movable crosshead) 15 that can be raised and lowered along the guide rod 13A, and a constant temperature bath 23 of a temperature control device 17 is installed on the upper surface of the container holder 15. The container 12 is held in a constant temperature bath 23. 24 is a container holder.

The dynamic contact angle measurement device 10 also includes a pulse motor 25 and a feed screw 26 that constitute the lifting drive section 16 at the lower part of the pedestal 13, and the feed screw 26 driven by the motor 25 is attached to the container holder 15. It's screwed on. The motor 25 is equipped with an encoder 27.

Further, the temperature control device 17 is configured as shown in FIG.
8 is drawn into a heat exchanger 29, and the temperature of the heat medium inside the constant temperature bath 23 is set to a desired temperature state.

In addition, in the dynamic contact angle measuring device 10, the load cell 14 and the container pedestal 15 are covered with a windshield cover 30.

The control device 18 is composed of, for example, a microcomputer, and as shown in FIG.
(readable/writable memory) 33, an input/output device 34, and is also provided with a keyboard 35, an X-Y display section (X-Y plotter, X-Y recorder) 36, and a printer 37. The control device 18 drives and controls the motor 25 based on operation commands applied via the keyboard 35 .

Further, the control device 18 receives the output of the load cell 14 via the amplifier 38 and also receives the output of the encoder 27, thereby forming a calculation section.
That is, the control device 18 controls the load cell 1 when the container pedestal 15 is raised and lowered, as will be described in detail below.
4, the surface tension when the sample 11 is immersed or pulled up in the liquid is determined based on the change in the load detection signal, and the contact angle of the liquid under a specific temperature condition is determined based on this surface tension. calculate.

Hereinafter, a procedure for measuring a dynamic contact angle using the dynamic contact angle measuring device 10 will be described.

A sample 11 of a polymeric material or the like is thinly coated on a cover glass. This sample 11 is suspended and supported by a load cell 14 via a hook 20 and a flexible connector 21.

For example, a container 12 containing pure water (purified into ultrapure water using a pure water production device after ion exchange) is held in a constant temperature bath 23 installed on a container pedestal 15 .

The motor 25 of the lift drive unit 16 is driven, and the container 12 approaches (raises) or separates (descends) from the sample 11 suspended from the load cell 14 at a constant speed.

The output of the load cell 14 and the displacement of the container holder 15 (output of the encoder 27) are transferred to the memory of the control device 18 in synchronization with each other and stored as a load F-displacement δ curve as shown in FIG.

When the container pedestal 15 rises and the lower end of the sample 11 touches the water surface of the container 12 and a meniscus is formed, interfacial tension is observed. The formation of a meniscus on the water surface of the sample 11 at this time and the force acting on the sample 11 are shown in FIG. 4. The forces F1, F2, and F3 acting on sample 11 in Fig. 4 are
P = 2 (t + w), the surface tension of water is γ, the contact angle is θ, the mass of sample 11 is m, sample 1
When the buoyant force acting on 1 is Fb, it becomes as follows.

F1=mg...(1) F2=mg+Pγcosθ...(2) F3=mg+Pγcosθ−Fb...(3) In the above, the advancing contact angle θA is estimated from the interfacial tension FA generated when sample 11 contacts the water surface. Ru.

cosθA=FA/Pγ (4) Furthermore, when the sample 11 is immersed in water, the tension decreases because it becomes lighter by the amount of buoyancy. When the sample 11 reaches a certain depth and the container pedestal 15 begins to descend, the buoyant force decreases and the observed tension increases. At this time, the receding contact angle θR is evaluated from the tension FR when the sample 11 separates from the water surface.

cosθR=FR/Pγ...(5) Here, the above tensions FA and FR can be calculated from the load F-displacement δ curve stored above by the buoyancy slope line s1,
It is determined as the intersection of s2 and the immersion start point F0.

The immersion start point is determined from the load F-displacement δ curve as shown in FIG. 5 by reading the change in tension F0 when the sample 11 contacts the liquid surface. The setting of this tension change F0 can be changed within a range that does not impede the measurement accuracy of this device 10, so that the immersion starting point can always be read stably against disturbances such as external vibrations.

Next, the operation of the above embodiment will be explained.

According to the above embodiment, when the sample 11 suspended and supported by the load cell 14 is immersed or pulled up into a liquid and the load acting on the sample 11 is measured, the liquid container 12 is moved without moving the load cell 14. I decided to move it. Therefore, as described above, the influence of the acceleration α and the vibration of the sample 11 that occur when the sample 11 and the container 12 are brought close to each other/separated from each other on the detected load of the load cell 14 can be eliminated, and the surface characteristics of the sample 11 can be eliminated. The load cell 14 can stably measure only changes in the load caused by this.

[Effects of the invention] As described above, according to the invention, when a sample suspended and supported by a load cell is immersed or pulled up into a liquid and the load acting on the sample is measured, the load that is applied to the sample is measured. Only changes in load can be stably measured using a load cell.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing an example of a dynamic contact angle measuring device, Fig. 2 is a block diagram showing a control system of the dynamic contact angle measuring device, Fig. 3 is a piping diagram showing a temperature control device, and Fig. 4 is a schematic diagram showing the load acting on the sample,
FIG. 5 is a diagram showing the dynamic contact angle hysteresis loop, FIG. 6 is a schematic diagram showing the influence of acceleration acting on the sample, and FIG. 7 is a schematic diagram showing the displacement of the load cell. 11...sample, 12...liquid storage container, 13...
... Frame, 14... Load cell, 15... Container holder, 16... Lifting drive section, 19... Fixed cross head.

Claims (1)

[Scope of utility model registration request] It has a load cell that suspends and supports the sample, and a container pedestal that supports the liquid container, and by moving the load cell and container pedestal relative to each other, it measures changes in the load that acts on the sample that is immersed or pulled up in the liquid. A load measuring device comprising: a load cell fixedly disposed on a pedestal; a container holder disposed on the pedestal so as to be movable up and down; and a lifting drive section for raising and lowering the container holder.